Vectra C Throttle Body (Throttle Position Sensor)

Cass

Hey all. Looking for, well, anything. Advice, help, opinions, tips, etc.

Car went in for it's NCT today. Was expecting nothing but good things, BUT the guy comes back with a Fail/Refusal. I was stunned. Car flew it last year and it's done less driving and been better kept this year. Not to mention over €800 on new parts & tyres in the last couple of months.

The problem was the tester could not get an emissions reading, as such the car is classed as fail/refused. When I asked how he cannot get a reading he said there is an issue with the throttle. He explained that the car will not hold a constant rev at the required level to test. He said it starts to slowly rise in revs so he cannot get a constant and set reading.

I went home and tested it myself. Here is what I found.

It runs high when first started from cold (around 1,100 - 1,200 rpm) and quite quickly settles into an idle rev of 700 rpm. When I push the accelerator pedal there seems to be a "lag" but the revs climb. If I hold the pedal steady with the rev counter at 2,200 rpm or less it stays there without issue. As soon as I rev it above 2,300, lets say 2,500, it revs to that rpm, then without my pressing harder on pedal it climbs. Slowly, but surely. Eventually it comes to a rest at approx. 3,000 rpm. If I press the pedal again it'll climb higher and continue to rise a little bit more, when I've stopped pressing the pedal, until it again comes to rest at a higher rev than the pedal position should allow for.

Then an interesting thing caught my attention. When I release the pedal, at any rev, the revs stay where they are for about 1-2 second and slowly start to drop. At this point I have my foot off the pedal and the revs are dropping, but slowly. If I give the pedal a quick sharp push the rev counter almost doesn't move, whether from idle or alternating between various revs (although there is slightly more of a response when doing this from idle). If I floor the pedal, not stomping it just pushing it quickly, and then as quickly release it the rev counter and engine barely rev up past 1,100 - 1,200. IOW the delay between what I do with my foot and when the engine acts is a couple of seconds. So by the time it "knows" to rev up, my foot is off the pedal and it starts to wind down (before it's actually rev'ed up).

When the engine has settled on 3,000 rpm (example) regardless of my foot position and I begin to lift my foot of the pedal, the revs begin to slowly drop. However if I give a sharp press of the pedal as the revs are dropping, then take my foot off the pedal (not fully) as quick the revs never rise up at all, and simply continue to fall.

So I took off the air intake pipe, and there was some dirt/fouling/gunk around the butterfly valve and on the plate. I cleaned it thoroughly and inside and around the pipes. Then reconnected everything. I thought the throttle position sensor (TPS) would be external, but could not find it. I now know it's an integral part of the unit and as a sealed unit (only the jack plug extend out) cannot be removed, replaced on it's own.

So to the questions.

1. Would this be the cause of the "climbing" revs?
2. If not anything else that would cause this?
3. If it is the cause can these be repaired?
4. If so anyone any recommendations?
5. If not and a new unit is needed anyone any suggestions as to where to go for one as the prices I've found so far range from €450 upward.

I'm not one to skimp on parts, but after throwing over €800 into the car in the last 2 months, and not exactly being flush i'm trying to fix it right, but with costs as low as possible. Reason is simple, motor tax is due at the end of the month, so is the mortgage payment, and after Mother's day, 2 birthdays, and a loan to a family member so they can move house it's been a tight, tight month.

I see lots of second hand ones on Flea-bay, etc. but if i'm going to go second hand or refurbished i'll buy local so I have comeback and waiting for postage if there is an issue or return is a non runner. If this is not possible then so be it. I'll book the test as late as possible, then request a date as close to the end of the 30 day period to allow as much time as possible to get the few quid together. However I don't want to go through all that only to find the TPS is not the issue.

I never noticed the issue before the test, and what annoys me is it passed last year so the fault is/must be recent. The car drives well, and performance & economy are not effected. Well if they are it means it'll perform even better, when fixed, than it is now.


Picture of the unit in my car and a link to the one I need.

Link






Thanks in advance for any info.

dieselbug

Hi Cass

Lots of detail in your post but you dont say what year the car is and which engine.

I think your first step should be to check for any fault codes that may be stored, record them and clear them and check again after a bit of driving to see if any have returned.

Some of these can have the faults read by pressing the throttle and brake pedal and counting the flashes or something like this.

Did this car have a flat battery or have the battery replaced or disconnected anytime recently?

Cass

dieselbug wrote: »

Hi Cass

Lots of detail in your post

I try to cover as much as I can, but sometimes run away with the length of the post so apologies for the short novel.

but you dont say what year the car is and which engine.

Ball.

It's 2004, Vectra C, 1.8 petrol, GTS, z18xe. I think that is all the names, etc. associated to it.

I think your first step should be to check for any fault codes that may be stored, record them and clear them and check again after a bit of driving to see if any have returned.

That would be the first advice I would give too, but you know that old saying about "do as I say, not as I do". I'm kinda annoyed, and pissed off, and now in a hurry to resolve this. IT's stupid, and there is no reason for me to be like this, but I pretty sure the fault lies in the throttle body/TPS.

Some of these can have the faults read by pressing
the throttle and brake pedal and counting the flashes or something like this.

Doesn't work on mine. Tried it twice and nothing.

Did this car have a flat battery or have the battery replaced or disconnected anytime recently?

It did.

I found the battery was always sluggish to start the car. If I turned the ignition on (anytime, hot or cold, etc) and left it on for more than say 7 - 10 seconds she nearly wouldn't turn over. I changed the battery to a higher amp one and problem solved. Car turns over without an issue and the sluggish start with the ignition on for any period of time does not cause an issue.

This was about 7 months ago.

dieselbug

You may well be correct in believing the problem is the throttle body, but....It would be poor practice to fit a new one on a hunch even if it's a good one and poor advice from me to agree with you.

The reason I asked about the battery is the throttle body may need an adaption after a disconnection as it's learned values may be lost.

But my advice is still to get it scanned and look at values for the throttle sensor, MAP, check egr etc. Doesent this car also have manifold intake flaps? another potential problem area.

Clean the throttle body, get it scanned and a throttle body adaption carried out, it may be money well spent.

Cass

dieselbug wrote: »

You may well be correct in believing the problem is the throttle body, but....It would be poor practice to fit a new one on a hunch even if it's a good one and poor advice from me to agree with you.

I apologise if any of what i said came across as "feck off, i'm doing it my way". That is not my intent. I have a friend, locally, that used to work for Opel and he has the diagnostics tool with tech 2 on it (which i believe is one of, or the latest tool needed). I'm going to try him first as i've had time to calm down. Just absolutely annoyed that such a small problem went unnoticed by me, caused my car to be refused, and costs so much if i have to buy new. All the work i done was "unnecessary". By that i mean i wanted to replace them to know it was done, and done right. The car would have passed with the old parts on it.

The reason I asked about the battery is the throttle body may need an adaption after a disconnection as it's learned values may be lost.

Ah yeah. I know about that. It's meant to relearn itself usually within 20 - 30 minutes of normal driving, but i get what you're saying.

But my advice is still to get it scanned and look at values for the throttle sensor, MAP, check egr etc. Doesent this car also have manifold intake flaps? another potential problem area.

Not too sure actually. Must check. Seems the z18xe has slight variances against other Vectra models as i learned when i checked the TPS prices and availability.

Clean the throttle body, get it scanned and a throttle body adaption carried out, it may be money well spent.

I gave it a wipe in situ, but as i don't have a gasket and due to the fact i might damage the one in it i cannot clean until i get a spare. However it will be one of the first things on the menu.


As said above the car runs well. No chugging, spluttering, failure or laboured starting, nothing. Economy is approx 40.8mpg, and acceleration is by no means slow. The highlighting of the issue with the throttle body and TPS has me thinking and i'm remembering back and wondering if it caused some "issues" i remembered. For example while the acceleration is good i notice that when i keep my foot on the pedal at a certain point if the car goes pass a set rev range it starts to accelerate more without me pushing the pedal. Like the turbo lag you'd experience in a car with a turbo.

Also when overtaking is the delay between when i push the pedal to when the car accelerates down to this?

It's the reason i'm so sure (or think i am) it's the TPS. You know one of those things that you never cop yourself, but when it's pointed out there could be an issue you start to put 2 & 2 together.

dieselbug

No I didnt read your post that way at all.

But it goes against the grain to just fit parts without proving first they are the parts causing the problem. ideally test, test, test first and prove your diagnosis.

Tech 2 will be ideal for this car, may also be worthwhile to get him to check the software is the current one for this model.

MAP sensor is a typo should have read MAF I dont think this model has a MAP.

There are some variences of this engine and some will differ from others.

Let us know how you get on.

Cass

PukkaStukka wrote:

If its hunting up and down like a sine wave then get someone with a scan tool or scope to check the O2 sensor."

Hey Pukka. She is not hunting at all. She starts well, runs well, and the economy is pretty good as outlined above. I don't pretend to be a mechanic but i'd imagine if it was the O2 sensor etc. she would be showing hunting signs like you describe (hope that is not a jibe because i'm the Mod of shooting/hunting )

dieselbug wrote: »

No I didnt read your post that way at all.

Who could blame you. I got bored reading it. TL:DR.

But it goes against the grain to just fit parts without proving first they are the parts causing the problem. ideally test, test, test first and prove your diagnosis.

You're dead right and i'm in the process of getting her tested and trying to source a gasket for the throttle body incase i damage the one on it. I intend to strip it down, clean the crap out of it (literally) and rebuild to see if it's something as simple as gunk build up in the pipes/intakes.

Tech 2 will be ideal for this car, may also be worthwhile to get him to check the software is the current one for this model.

Will do.

MAP sensor is a typo should have read MAF I dont think this model has a MAP.

It's the MAF sensor alright, but i'm following ya so far.

There are some variences of this engine and some will differ from others.

Tell me about it. On some models the TPS sensor is mounted onto the side of the throttle body, but not contained within it. It's a two screw, and €40 fix. Because mine has it built into the body it's a €500 fix (new). Hence the reason i'm not jumping in with both feet. Even if i had the cash i wouldn't do that as it goes against the grain to replace without checking.

Let us know how you get on.

Will do and if anyone has any recommendations regarding checks, repairs, refurb, new, etc please feel free to post. Something local/Irish as time is a factor.

Cass

Just back from Opel mechanic. He ran the diagnostic, and got nothing. Not one fault. No codes to clear, no issues detected. He took it for a spin (about 10 mins) and came back and still nothing. He held the throttle pedal and while it took a little "finesse" it held at the desired range of revs.

He asked about performance, economy, hunting, etc. and when i told him i'm getting no issues and good performance he simply said "i cannot find anything to fix or even look at. As far as i'm concerned there is no reason the car could not have been tested".

So looks like i'm back onto the NCT crowd to ask for another test. I believe i can question the validity of the test if i'm not happy with it and can show the reason why, but me being me, i'm wondering whether to go through that process as it requires paying the full fee again (refundable if the car passes, not if it fails again), and to have the last test questioned then go back to the place where it was tested originally and possibly the same tester whether there will be "issues". OR just pay for the re-test and stick her back in as is?

Cass

Update number two.

Retest done yesterday and it failed again. The guy was spot on and took time to test it properly. He got it held at a rev between 2500 - 3000. She passed everything else, and under idle it passed without any issue. He said the issue comes from the high rev. Bear with me on this.

He said that the car is still revving unusually (hunting if you will) at the high rev. I don't like the idea of how they test the car in the NCT. No car should be highly revved in idle without a load on the engine. It's not good for it. It concerned me a little as he was at it for quite a while and Vectra C's are prone to heating up on a good day. Not overheating, but the temp will rise when in stationary traffic. The fan always kicks in at the designated temp, but still. Anyway he said that on the last test the lambda reading was 1.25 and on this it was 1.08. That is still outside the 0.97 - 1.03 range.

Now as the tester the last time never completed the emissions test i never copped this and as soon as he told me i immediately started to think it's nothing to do with the throttle body or TPS, but the MAF or one of the lambda sensors. While no code appeared on the diagnotic that it not unusual. I'm starting to think that one of the lambda sensors is not running right (dirty, burnt out, etc) and because it's giving inconsistent readings to the ECU the engine is revving up to "compensate" for the misreadings it's getting from the sensor. So it's running rich.

The thing is after weeks (actually months) of brimming the car, driving and brimming i can say she is doing 8.9 miles to the litre. So 40.5 miles to the gallon. That is an average of high and low readings from the last 10 fills. So whatever issue there is is so sublte it's not showing codes and not effecting performance (or to a detrimental level).

In retrospect i have to put my hands up and say dieselbug was spot on. Had i listened to someone say then done as i did without having it properly checked before hand i'd have said they were throwing good money after bad. However i have it going back to the Opel mechanic tomorrow, with all the information and to narrow down which part exactly is the issue. I'd rather not have to fork out the price of new parts, but i'm skeptical of using second hand ones and suffering another possible fail. So prices for the lambda's i've gotten are on average €50 each and for the MAF between €135 to €250. Depending on brand.

One other question. After the retest what way am i fixed ffor another retest? Is it a full test now or another retest?