Need help understanding diagnostics

tomo92

My car failed it nct on high lambda 1.09 HC 8PPM both at low/high idle and CO was 0.00 again at low and high idle, I've had to go out and buy a diagnostic scanner as any mechanic in the local area doesn't really want to help me solve this problem, my diagnostic is showing at idle:

DTC_ CNT 0
FUEL SYSTEM1 CL
LOAD_PCT% 12.2
ETC ℃ 66
SHRTFT1% 0.0
SHRTFT3% -100.0
LONGFT1% 11.7
LONGFT3$ -100.0
RPM(/MIN) 765
VSS(KM/H) 0
SPARK ADV 2
IAT ℃ 38
MAF(G/S) 1.93
TP(%) 2.7
02S1B1(V) 0.115
SHRTFT B1S1 (%) 1.6
02B1S2(V) 0.410
SHRTFTB1S2 (%) -100

My 02 sensor upstream steadies at 0.035 after having the car on for say 10/15 mins and doesn't move even if gas is applied I'm also getting a code p0170 I have absolutely no idea what to look for looking at these readings and to be honest I don't have the money or the time to trial and error swapping the 02 sensors or the MAF etc. Any help would be appreciated. The car is a 1.8 opel vectra petrol.

Waterson

The high lambda reading of exhaust emissions indicates a surplus of oxygen, or conversely a lack of fuel. The p0179 code I dictates that the fuel trim (which on your scanner is shown by SHRTFT is outside of acceptable parameters). The 11.7% figure at idle 767 rpm means the computer is commanding the fuel injectors to stay open for longer, adding 11.7% more fuel than its baseline setting. This is a good indicator of the nature of your problem. The lambda sensor is reporting back a surplus of oxygen. This could either be an accurate reading, in which case you need to check things like fuel pressure at the rail, or a false reading, which means the lambda sensor itself is faulty.

blackbox

Waterson wrote: »

The high lambda reading of exhaust emissions indicates a surplus of oxygen, or conversely a lack of fuel. The p0179 code I dictates that the fuel trim (which on your scanner is shown by SHRTFT is outside of acceptable parameters). The 11.7% figure at idle 767 rpm means the computer is commanding the fuel injectors to stay open for longer, adding 11.7% more fuel than its baseline setting. This is a good indicator of the nature of your problem. The lambda sensor is reporting back a surplus of oxygen. This could either be an accurate reading, in which case you need to check things like fuel pressure at the rail, or a false reading, which means the lambda sensor itself is faulty.

I'm not too sure about interpreting all the diagnostics, but if on board lambda is reading high as well as the NCT lambda reading high, it is less likely to be a lambda probe fault. My experience is that a high NCT lambda reading is likely to correspond to an erroneous low on board lambda reading that causes the injectors trim back. Another potential cause of high lambda is an exhaust leak.

tomo92

Waterson wrote: »

The high lambda reading of exhaust emissions indicates a surplus of oxygen, or conversely a lack of fuel. The p0179 code I dictates that the fuel trim (which on your scanner is shown by SHRTFT is outside of acceptable parameters). The 11.7% figure at idle 767 rpm means the computer is commanding the fuel injectors to stay open for longer, adding 11.7% more fuel than its baseline setting. This is a good indicator of the nature of your problem. The lambda sensor is reporting back a surplus of oxygen. This could either be an accurate reading, in which case you need to check things like fuel pressure at the rail, or a false reading, which means the lambda sensor itself is faulty.

I I've tested the lambda sensor the two white wires with a multi meter and they are fluctuating up and down so does that mean it is working, I had brought it up to a Suzuki garage which will cost me a fortune when I get the bill , and they said the faults that are coming up is p0170 and p0100 intermittent (maf sensor) would a faulty maf sensor drive the lambda high at nct? could this be resolved by putting in a new air flow meter as suggested by them or should I take what they are saying with a pinch of salt.

tomo92

blackbox wrote: »

I'm not too sure about interpreting all the diagnostics, but if on board lambda is reading high as well as the NCT lambda reading high, it is less likely to be a lambda probe fault. My experience is that a high NCT lambda reading is likely to correspond to an erroneous low on board lambda reading that causes the injectors trim back. Another potential cause of high lambda is an exhaust leak.

When I took the car for nct, I got the fail sheet and there was a few bits to be done two brackets snapped of the exhaust but I had them welded on and the mechanic doing it checked for pin holes and he found one up on top of the exhaust, but he filled it and lambda is still high.

jimgoose

Test the MAF sensor with a multi-meter, like I told you last Wednesday!

DublinDilbert

tomo92 wrote: »

I I've tested the lambda sensor the two white wires with a multi meter and they are fluctuating up and down so does that mean it is working, I had brought it up to a Suzuki garage which will cost me a fortune when I get the bill , and they said the faults that are coming up is p0170 and p0100 intermittent (maf sensor) would a faulty maf sensor drive the lambda high at nct? could this be resolved by putting in a new air flow meter as suggested by them or should I take what they are saying with a pinch of salt.

Sounds like your lambda sensor is working fine, switching at 1Hz or so between lean and rich. The MAF is ethier faulty or has a bad connection between it and the ECU. Time for a multi-meter to make sure the MAF is getting a power supply and see what voltage is coming back from it.

this any help?
http://easyautodiagnostics.com/suzuki/2.5L/how-to-test-the-maf-sensor-1

tomo92

As I don't have a wire piercing probe, I used a sewing needle with the 02 sensor I'm guessing it wouldn't do any harm doing the same with the MAF?

tomo92

jimgoose wrote: »

Test the MAF sensor with a multi-meter, like I told you last Wednesday!

I know what u told me last Wednesday but u didn't actually explain how I would go about doing it!. I wouldn't be the handiest with electrics or cars there something I can't turn my hand to I'd rather give someone a couple a €€ and problem solved

jimgoose

tomo92 wrote: »

I know what u told me last Wednesday but u didn't actually explain how I would go about doing it!. I wouldn't be the handiest with electrics or cars there something I can't turn my hand to I'd rather give someone a couple a €€ and problem solved

I explained the different wires and what kind of voltages you were looking for on each one, IIRC? Anyway, DublinDilbert has posted as good a video as you'll find on the subject. Good luck with it.

Waterson

blackbox wrote: »

Another potential cause of high lambda is an exhaust leak.

Absolutely agree with you. Im assuming that the OP's mechanic would have checked for a exhaust leak upstream of the sensor. Reading through the subsequant posts it seems theres more to this than was alluded to in the original post.

Waterson

Just had another look at the freeze frame the OP posted. The car is at idle and warm (66 degrees). The reading from the upstream sensor is 0.115 V. Sensor should ideally flip flop between 0.2 and 0.9v...could this be down to the lean emission or a faulty sensor? What car is this?

tomo92

Waterson wrote: »

Just had another look at the freeze frame the OP posted. The car is at idle and warm (66 degrees). The reading from the upstream sensor is 0.115 V. Sensor should ideally flip flop between 0.2 and 0.9v...could this be down to the lean emission or a faulty sensor? What car is this?

I had replaced the the upstream sensor with a genuine opel one and it failed again so I had to go to a different mechanic which looked at the two fail sheets I had and then checked the cat and it was clogged with all this white stuff, and also on his diagnostics it came up as a intermittent fault with the air flow meter, the car is a 1.8 opel vectra

tomo92

And most recent nct results with new upstream 02 sensor:

Low idle (740) rpm
CO: 0.00%
HC: 8ppm

Lambda 1:16

Fast idle test (2830)rpm
CO: 0.00%
HC: 7ppm

blackbox

Exhaust is way too lean.

If the engine is running lean I'd expect car to be down on power and possibly hesitating on throttle. Also, spark plugs should show symptoms of being over lean. Likely causes MAF, Lambda sensor.

If engine is running perfectly, the problem is probably downstream of engine - i.e. leak in the exhaust system - maybe cracked manifold or split flexi.

tomo92

blackbox wrote: »

Exhaust is way too lean.

If the engine is running lean I'd expect car to be down on power and possibly hesitating on throttle. Also, spark plugs should show symptoms of being over lean. Likely causes MAF, Lambda sensor.

If engine is running perfectly, the problem is probably downstream of engine - i.e. leak in the exhaust system - maybe cracked manifold or split flexi.

The car will hesitate when started from cold for maybe the first 30 seconds to a minute and then it picks up, but if I am driving down motorway car hesitates unless I have the throttle pushed straight to the floor, I have went to 3 different mechanics now as my usual mechanic has closed up shop, and the first 2 mechanics say it was the upstream 02 sensor so I replaced with one of the internet and it wasn't the right one, so I replaced it with a genuine opel one €150, and the lambda reading was higher than previous, so I brought the car to a third mechanic and he said it was the catalytic converter, but I've done a little reading on it and if the cat was clogged shouldn't the HC and CO be alot higher.

jimgoose

Has the MAF been checked or swapped out?

tomo92

Could a faulty maf sensor cause such a high lambda reading? I have a scanner with live data and the car stays in OL_ FAULT I assume that would have something to do with either the 02 sensor or maf?

tomo92

jimgoose wrote: »

Has the MAF been checked or swapped out?

The MAF has been swapped with one from the local scrap and it ran worse than the one originally in the car.

jimgoose

tomo92 wrote: »

The MAF has been swapped with one from the local scrap and it ran worse than the one originally in the car.

And what does that tell you?

tomo92

jimgoose wrote: »

And what does that tell you?

My sensor is better than the 1, from the scrap yard, and btw if you don't have anything that might be helpful towards the situation don't bother commenting trying to be a f***ing smart a*se

jimgoose

tomo92 wrote: »

My sensor is better than the 1, from the scrap yard, and btw if you don't have anything that might be helpful towards the situation don't bother commenting trying to be a f***ing smart a*se

It tells me the scrap one is furked and the experiment failed because it told you nothing useful. That will be the end of my smart-arsery. There's no helping some people.

tomo92

jimgoose wrote: »

It tells me the scrap one is furked and the experiment failed because it told you nothing useful. That will be the end of my smart-arsery. There's no helping some people.

I wouldn't have put this post up if I wasn't looking for help, when people are asking questions that are to make me look stupid thats a little annoying, I'm not a mechanic I can do basic bits with cars that's all, emissions definitly not that's exactly why I'm trying to finding the source of the problem on here as mechanics are all saying different things.

jimgoose

tomo92 wrote: »

I wouldn't have put this post up if I wasn't looking for help, when people are asking questions that are to make me look stupid thats a little annoying, I'm not a mechanic I can do basic bits with cars that's all, emissions definitly not that's exactly why I'm trying to finding the source of the problem on here as mechanics are all saying different things.

I'm not trying to make you look stupid and I apologise if I gave that impression. I'm trying to lead you along the lines of thinking about the problem like an engineer, as opposed to running around to endless mechanics who don't know much more about it than you do. And I think that MAF sensor could be the root of the trouble. Test it, have it tested, or replace it with a known good one.

tomo92

jimgoose wrote: »

I'm not trying to make you look stupid and I apologise if I gave that impression. I'm trying to lead you along the lines of thinking about the problem like an engineer, as opposed to running around to endless mechanics who don't know much more about it than you do. And I think that MAF sensor could be the root of the trouble. Test it, have it tested, or replace it with a known good one.

Its grand, to be honest I'm fed upto f**k with it now at this stage 3 mechanics already 2 said 02 sensor replaced with a genuine part the third says the cat is clogged and also the MAF sensor but the maf sensor doesn't show on my scanner only p0170, as the car is a 04 and I've put 500 quid into it so far I don't want to put a cat in it and a genuine maf sensor and the problem is still there,

John T Carroll

blackbox wrote: »

Exhaust is way too lean.

If the engine is running lean I'd expect car to be down on power and possibly hesitating on throttle. Also, spark plugs should show symptoms of being over lean. Likely causes MAF, Lambda sensor.

If engine is running perfectly, the problem is probably downstream of engine - i.e. leak in the exhaust system - maybe cracked manifold or split flexi.

It has alot of the hall marks of air dilution, the op might look at his last (passed) NCT and compare the CO & HC with his very low readings now and that will give him a good clue. Normally, an engine fitted with two 02 sensors will flag a fault code if there is genuine emission problem as the cat is working harder and there will be a "mismatch" between the two sensors.
My familys Bora with > 180K miles failed on high lambda (only one sensor on this model) but had miracusouly low CO & HC figures, even though there were only apparently tiny pin holes in the rear box I replaced it and it passed the NCT and the CO & HC figures increased but were still within limits.

tomo92

John T Carroll wrote: »

It has alot of the hall marks of air dilution, the op might look at his last (passed) NCT and compare the CO & HC with his very low readings now and that will give him a good clue. Normally, an engine fitted with two 02 sensors will flag a fault code if there is genuine emission problem as the cat is working harder and there will be a "mismatch" between the two sensors.
My familys Bora with > 180K miles failed on high lambda (only one sensor on this model) but had miracusouly low CO & HC figures, even though there were only apparently tiny pin holes in the rear box I replaced it and it passed the NCT and the CO & HC figures increased but were still within limits.

I've seen alot online and a high lambda reading suggests a leak in the exhaust, I've looked at the previous sheet which it passed and the HC is 8ppm and the CO is 0.08% and the lambda for that test is 1.03 ( scraped past) I've had the exhaust checked and they said there's no leaks, but the car does sound abit like a diesel car, could maybe the exhaust manifold have a leak, as I've put my hand over the exhaust and not seen anything blown out from any part of the exhaust.

John T Carroll

tomo92 wrote: »

I've seen alot online and a high lambda reading suggests a leak in the exhaust, I've looked at the previous sheet which it passed and the HC is 8ppm and the CO is 0.08% and the lambda for that test is 1.03 ( scraped past) I've had the exhaust checked and they said there's no leaks, but the car does sound abit like a diesel car, could maybe the exhaust manifold have a leak, as I've put my hand over the exhaust and not seen anything blown out from any part of the exhaust.

It can certainly be a pain tracking down some of these faults........ the needle test you did on the upstream 02 sensor is quite a good one, if the reading is flip/flopping constantly between say 0.2V and 0.9V and assuming that the O2 sensor is correct then the fuel injection period is constantly increasing/decreasing to keep the fuel mixture correct, that's how all fuel injection systems work, this should result in a Lambda reading of 1.0 in a perfect world but obviously any air leak upstream of this will indicate a lean mixture and the fuel trim will increase based on the reading that its getting. There might be some evidence of this in the +11.7% fuel trim reading, I think a fault code is flagged if its >10%, I wouldn't get too hung up on that just yet, you might try disconnecting the battery for 20 mins or so, this will reset the LTFT (long term fuel trim) and then reconnect the battery and go for a spin to warm up the engine and then take another diagnostic and see what readings you get, also carry out that needle test again (on upstream O2 sensor) and ensure that its constantly flip/flopping. Also check any vacuum hoses thoroughly for any cracks etc. Don't know if you were able to verify that the MAF sensor is OK or not by taking voltage readings. In my experience re vacuum leaks I have found that if the idling speed is say 750 RPM to 850 RPM, then the engine will idle almost exactly at the lower limit if there are no leaks.
I don't want to go on and on as this can only lead to confusion but generally speaking if you have plenty of patience then you will sort it out, best of luck.

tomo92

John T Carroll wrote: »

It can certainly be a pain tracking down some of these faults........ the needle test you did on the upstream 02 sensor is quite a good one, if the reading is flip/flopping constantly between say 0.2V and 0.9V and assuming that the O2 sensor is correct then the fuel injection period is constantly increasing/decreasing to keep the fuel mixture correct, that's how all fuel injection systems work, this should result in a Lambda reading of 1.0 in a perfect world but obviously any air leak upstream of this will indicate a lean mixture and the fuel trim will increase based on the reading that its getting. There might be some evidence of this in the +11.7% fuel trim reading, I think a fault code is flagged if its >10%, I wouldn't get too hung up on that just yet, you might try disconnecting the battery for 20 mins or so, this will reset the LTFT (long term fuel trim) and then reconnect the battery and go for a spin to warm up the engine and then take another diagnostic and see what readings you get, also carry out that needle test again (on upstream O2 sensor) and ensure that its constantly flip/flopping. Also check any vacuum hoses thoroughly for any cracks etc. Don't know if you were able to verify that the MAF sensor is OK or not by taking voltage readings. In my experience re vacuum leaks I have found that if the idling speed is say 750 RPM to 850 RPM, then the engine will idle almost exactly at the lower limit if there are no leaks.
I don't want to go on and on as this can only lead to confusion but generally speaking if you have plenty of patience then you will sort it out, best of luck.

You can say that again a pain in the a*se, I have tested the new one and it's switching on the multimeter and also on the scanner I have, but the car still shows OL_ FAULT on the scanner, I have checked again today for vacuum leaks absolutely nothing I can't see anything wrong, what I did see was on the flexi pipe on exhaust is covered in gun gum so started the car hopeing I hit the jackpot and nothing came from it I held me hand around it that long it nearly stuck to it, the idle is fine when started cold the idle goes from 1100-1200 rpm back down to normal no hunting from the car or revs going up and down, the mechanic said there is a code for the MAF sensor but it doesn't show that code on my scanner only the p0170 so il check the MAF tomorrow and see if that might be the problem.

greasepalm

you mentioned a stuffed cat are you using a 5w-30 engine oil and topping up oil very regulary.
does car do short journeys and not a good long burn.
thinking something like cataclean to clean exhaust system out.

http://reviews.halfords.com/4028/616247/reviews.htm

tomo92

greasepalm wrote: »

you mentioned a stuffed cat are you using a 5w-30 engine oil and topping up oil very regulary.
does car do short journeys and not a good long burn.
thinking something like cataclean to clean exhaust system out.

http://reviews.halfords.com/4028/616247/reviews.htm

I recently changed the oil 10w-40, she's topped up, I only own the car a month now and I don't do long journeys very often other than that I'd do maybe 20 miles a week in it, I put dipetane in it before the first nct would that be just as good as cat a clean

greasepalm

what year is car if its 2002 onwards you are using wrong grade of oil and clogging up egr and cat,modern engines use a low ash oil which leaves very little soot when burnt.gave up in using dipetane as it wont clean your cat.20 miles is nothing in a week.

tomo92

greasepalm wrote: »

what year is car if its 2002 onwards you are using wrong grade of oil and clogging up egr and cat,modern engines use a low ash oil which leaves very little soot when burnt.gave up in using dipetane as it wont clean your cat.20 miles is nothing in a week.

The car is 04 opel vectra 1.8 petrol and I don't think it has a egr valve, do you think I should change the oil and filter? I barely use the car but I need to have a car unless I'd be f**ked, 20 miles most weeks then sometimes the odd trip upto Dublin

greasepalm

get a can of cataclean and put into fuel tank when 1/4 full and go for a 20 mile drive,get a local garage to check emissions after to see how much it drops.
google egr valve shows one in your model.
because car is not driven for long causes exhaust to become clogged with contanements hence needing a motorway burn

tomo92

greasepalm wrote: »

get a can of cataclean and put into fuel tank when 1/4 full and go for a 20 mile drive,get a local garage to check emissions after to see how much it drops.
google egr valve shows one in your model.
because car is not driven for long causes exhaust to become clogged with contanements hence needing a motorway burn

Will do that first thing tomorrow and then have it checked, il look up Google now see if there is one where it's located, and what should I do with the oil change it out or leave until next service?

John T Carroll

tomo92 wrote: »

My car failed it nct on high lambda 1.09 HC 8PPM both at low/high idle and CO was 0.00 again at low and high idle, I've had to go out and buy a diagnostic scanner as any mechanic in the local area doesn't really want to help me solve this problem, my diagnostic is showing at idle:

DTC_ CNT 0
FUEL SYSTEM1 CL
LOAD_PCT% 12.2
ETC ℃ 66
SHRTFT1% 0.0
SHRTFT3% -100.0
LONGFT1% 11.7
LONGFT3$ -100.0
RPM(/MIN) 765
VSS(KM/H) 0
SPARK ADV 2
IAT ℃ 38
MAF(G/S) 1.93
TP(%) 2.7
02S1B1(V) 0.115
SHRTFT B1S1 (%) 1.6
02B1S2(V) 0.410
SHRTFTB1S2 (%) -100

My 02 sensor upstream steadies at 0.035 after having the car on for say 10/15 mins and doesn't move even if gas is applied I'm also getting a code p0170 I have absolutely no idea what to look for looking at these readings and to be honest I don't have the money or the time to trial and error swapping the 02 sensors or the MAF etc. Any help would be appreciated. The car is a 1.8 opel vectra petrol.

I am just looking again at what I assume are the two O2 sensor readings.....
02S1B1(V) 0.115 (upstream?)
02B1S2(V) 0.410 (downstream?)

I dont know how your diagnostics work but when the Bora failed on a Lambda of 1.1 I got hold of a VCDS and with that I could monitor the upstream (only one fitted) O2 sensor and dump the readings into a spreadsheet every 0.5 sec and then average the results which were 0.405V, this would be considered a bit low as I think 0.45V results in a Lambda of 1.0, anyway after replacing the rear box the average reading was still practically the same at 0.407V BUT the Lambda (NCT) was now 1.02, a pass. In your case I dont know why the diagnostics is showing a steady 0.115V whereas your needle test is flip/flopping correctly. Your downstream O2 sensor is showing a steady 0.41V, this would/could be correct as this a different type of sensor (wide band), now if that 0.41V is accurate then its quite close to what my average was and if there are no leaks downstream of it then I would be surprised if the NCT Lambda wasnt < 1.03.
Obviously you dont want to be just throwing money away so if you already havn't done so why dont you bring the car to one of these exhaust centres and get it up on their ramp and get them or yourself to look for any pin holes etc, you can always give them €10 or so if no leaks found.

greasepalm

as you have just changed oil and filter,just try cataclean and a burn first as having a cleaner system is a better start.

Waterson

From the emissions results, I don think your CAT is at fault, as you said the CO and HC readings are good, plus the reading from the downstream (post CAT) sensor is steady which is a good indicator of a correctly functioning CAT.
Its very easy to stop seeing the wood for the trees in these situations, so recapping:
You have a very lean running engine. This is why you have a lambda reading over 1.
You have a new genuine oxygen sensor fitted, so we can assume it is reporting back to the ECU correctly.
You have a power loss issue/hesitation throughout the rev range.
You have checked the entire exhaust system for leaks, (which the first mechanic confirmed) and apparently there are none, so that rules that out.
You have checked for vacuum leaks, which it seems based on the steady idle and no report of 'hunting' are not evident.
The MAF output can be chaned on a scantool live data. There should be an increase from 1.5 V at idle to around 4.5 V at open throttle along a relatively smooth curve.
Your car does have an EGR valve. It is very common for Opel valves to not seat properly due to carbon deposits. A valve stuck open would cause power loss issues as the air/fuel mixture is being diluted, but they usually log fault codes. There is a chance that your scantool may not be reading out all the codes. You may also experience cutting out when decelerating. Function of the EGR valve can be checked using live data. A comparision of EGR desired readings and EGR actual readings will show the position of the valve. It should be closed when idling and open at various RPM's as per its design parameters.
The next step would be to check the fuel system. Ask your mechanic to test the fuel pressure at the rail. The specs can be found online, I would imagine something like 3 bar would be acceptable. If fuel pressure is low, work back and check/change the fuel filter.
Following this, a check of the fuel injector function would be advisable.
All of these checks can be done without expenditure on new parts and is part of the diagnostic process for these faults. Im sorry you havent had a good experience with your other mechanics, but as much data as you can accumulate will help with the eventual diagnosis. Good luck sir.

tomo92

Just a update: I put in a can of cataclean yesterday and no noticeable difference, I have tryed to take the cat of and have a look on Sunday but I had all but one nut loosened but the head on it was rounded as I didn't really want to cut it so I just put it back on and left it as it was, so I looked underneath the car and the flexi had the mesh that should be attached to it was hanging on the downpipe and the flexi bit was covered it gun gum, I blocked the exhaust but I couldn't see that far up and as I didn't have a helper it was abit hard on my own, I took a look for the egr and cannot find it on the car I don't think the car has one I haven't checked the MAF yet that is next on the list, the mechanics were I am I think are looking to make easy money of me I think and at the end of day I still have the same problem with a lot less money in me pocket so I have decided to go to a mechanic up in Dublin in the next week or two I used him before for a few bits he's always steered me right

blackbox

If the flexi is dodgy that would be my main suspect.

NB as far as I know, cat does not significantly affect lambda readings - it mainly removes HC.

Have you looked at the plugs? You should be able to tell from them if it is running too rich or too lean.

John T Carroll

blackbox wrote: »

If the flexi is dodgy that would be my main suspect.

NB as far as I know, cat does not significantly affect lambda readings - it mainly removes HC.

Have you looked at the plugs? You should be able to tell from them if it is running too rich or too lean.

In general, if the emissions are OK and there is a high lambda with a properly working pre cat O2 analyser then in the vast amount of cases, the problem is downstream ie a holed exhaust.
tomo92,s Opel MAF is showing a flowrate of 1.93 G/sec, a 1.8 Litre engine idling at 765 RPM should, from my basic calculations, have an airflow of around 4.5 G/sec and that is why the LTFT is +11.7%, but having said all that, there is no reason, in my opinion, why the Lambda shouldnt be within spec. Long before any diagnostics, I used to stick my "needles" in lots of 02 sensors and if the reading was flip/flopping between say 0.2/0.9 volts then there was no problem there and the NCT Lambda was within spec.

tomo92

blackbox wrote: »

If the flexi is dodgy that would be my main suspect.

NB as far as I know, cat does not significantly affect lambda readings - it mainly removes HC.

Have you looked at the plugs? You should be able to tell from them if it is running too rich or too lean.

By looking at the flexi pipe and with the amount of gun gum that was on it ( the whole top half was covered with it) with what I've been reading online and what everyone has suggested on here that might be what the problem is. I did check the plugs and the tops of them were black and the threads were all oily.

tomo92

John T Carroll wrote: »

In general, if the emissions are OK and there is a high lambda with a properly working pre cat O2 analyser then in the vast amount of cases, the problem is downstream ie a holed exhaust.
tomo92,s Opel MAF is showing a flowrate of 1.93 G/sec, a 1.8 Litre engine idling at 765 RPM should, from my basic calculations, have an airflow of around 4.5 G/sec and that is why the LTFT is +11.7%, but having said all that, there is no reason, in my opinion, why the Lambda shouldnt be within spec. Long before any diagnostics, I used to stick my "needles" in lots of 02 sensors and if the reading was flip/flopping between say 0.2/0.9 volts then there was no problem there and the NCT Lambda was within spec.

The 3 mechanics I have went to, 2 of them said the maf sensor is showing a fault it just hasn't came up on my scanner only the p0170 code , maybe because my scanner wouldn't be as good as theirs I'm guessing, I will have to get a new sensor as the previous owner must of had the same problem as their is a scrap yard sensor in it from the marker that is on it, the new genuine 02 sensor is working perfect both on the live data scanner and also on the multimeter.

tomo92

Alright everyone something strange happened yesterday, I put €50 petrol in the car on Monday the most I put in the car since I bought the car and yesterday I was driving home and the engine light knocked of, so I had to do one more stop and after that I got back in the car and light was still of, would anyone know what this is all about because I literally can't get my head around it.

PukkaStukka

I noticed from your original post that the engine temp is indicated at 66c. Is that as hot as it gets? If so it might not run closed loop.

tomo92

PukkaStukka wrote: »

I noticed from your original post that the engine temp is indicated at 66c. Is that as hot as it gets? If so it might not run closed loop.

No that is a min or 2 after engine started

PukkaStukka

tomo92 wrote: »

No that is a min or 2 after engine started

What temp are you reading when its at normal operation? You need to confirm that its reaching and reporting normal operating temperature otherwise you won't get closed loop running and the emissions will be all over the place.

John T Carroll

PukkaStukka wrote: »

What temp are you reading when its at normal operation? You need to confirm that its reaching and reporting normal operating temperature otherwise you won't get closed loop running and the emissions will be all over the place.

You will always know when on open loop as both the STFT and the LTFT are both reset to 1.0, for fuelling calculations, for some reason the LTFT sometimes reads -100 on VAG cars at any rate, I checked out a Polo from cold a few weeks ago, it started out with a coolant temp of 7C and a STFT of 0.0. within 2.5 minutes it went to closed loop at a coolant temp of 30C, I dont know if it was the coolant temp triggered the closed loop or the fact that both O2 sensors were up to temperature.

PukkaStukka

John T Carroll wrote: »

I dont know if it was the coolant temp triggered the closed loop or the fact that both O2 sensors were up to temperature.

Yeah it's what the temp sensor sees coupled with no anomalies seen on the other sensors. It's best just to confirm that the OP is seeing correct temps when he connects in. Also, his scan tool might not be displaying non OBD / manufacturer specific codes that could help with the process here.

I don't know the Opel MAF that well but some MAF's need scoping rather than just voltage measurement. The airflow at idle showing at 1.2grams seems a little bit low to me.

tomo92

PukkaStukka wrote: »

What temp are you reading when its at normal operation? You need to confirm that its reaching and reporting normal operating temperature otherwise you won't get closed loop running and the emissions will be all over the place.

The car does go upto operating temperature, but when the car is driving it varies between 85℃ -90℃ and then when it is stationary it goes up to about 92℃ and the fan kicks in then

PukkaStukka

tomo92 wrote: »

The car does go upto operating temperature, but when the car is driving it varies between 85℃ -90℃ and then when it is stationary it goes up to about 92℃ and the fan kicks in then

And these numbers you are seeing on the scan tool tomo?