Passat intermittent power problem P0172

shamu2new

Hi

Any ideas what could be the problem here.
Ive a 2005 Passat (old model) 1.6 petrol. Got timing belt done then Coil pack replaced last year, then Oxygen sensor replaced about 3 months ago -car has been giving intermittent trouble coughing and losing power for a couple of seconds intermittently. There doesnt seem to be a pattern to when this happens. on a long drive recently the engine mgt light came on and gave a P0172 code but have done about 100 miles since clearing the light and it hasnt come back. Im debating whether to change it for an 07 or 08 as have spent a few quid on this car lately but there is only 85,000 miles on it.
Anyway - any ideas on what my next move should be - google says it might be a MAF problem?

Bobo78

May well be, you could try and clean it first to see does it helps.
It would also be recommended to clean your throttle body, idle air control valve and egr valve.
When you changed the coil pack did mechanic checked your spark plugs and leads?

shamu2new

thanks for that will get those checked over weekend. Light came back on this morning but car was driving ok? Yep the Leeds were replaced with coilpack at the time not sure about plugs though.

JP 1800

The P0172 code suggests that the system is running too rich, check for vacuum and air leaks but my hunch would be the MAF, get a cheap type from ebay for about 60 euro and see how you get on.

Bobo78

To be honest, from personal experiance I would never replace engine sensor such as MAF sensor with some unknown cheap unit from ebay. If it has to be replaced I would repalce it with orignal one or second hand one that s working properly. But I d always try with cleaning it first if it helps.

JP 1800

I understand your concern but cleaning a MAF rarely works, a cheaper unit will do the job but obliviously not as well as an OEM. If the cheaper MAF resolves the problem then the OP can buy an OEM one in the knowledge that they are not needlessly changing expensive parts.

shamu2new

Thanks for all the input so far - Im hoping to get a look tomorrow at this and will post an update

AzureAuto

Ideally remove all the guesswork and bring car to a decent mechanic with a scantool that can read live data values. The code indicates the vehicle is indeed running rich. Have the Long Term Fuel Trim values checked. If they are in negative double figures, the car's computer is trying to compensate for excess fuel/lack of oxygen in the system by subtracting fuel from the system, i.e. reducing on-time of injectors. Assuming O2 sensor is fine (again values can be checked in live data), systematically check car for vacuum leaks in pipes, condition of air filter and MAF readings. These should vary between 0-0.5 V at idle and 4.5-5V at wide open throttle conditions. makes sure there is a 5V feed going to the MAF connector with ignition on if not check engine management fuse.

shamu2new

Ok four months down the road after replacing the downstream sensor now the cat is going. Had diagnostics done and looks like I will need a new CAT. Anyone got any idea what kind of money Im looking at for this? Its a Petrol 1.6.

Nissan doctor

shamu2new wrote: »

Ok four months down the road after replacing the downstream sensor now the cat is going. Had diagnostics done and looks like I will need a new CAT. Anyone got any idea what kind of money Im looking at for this? Its a Petrol 1.6.

TBH it sounds like your original problem still hasn't been solved as cat failures are a symptom of another problem.

I would have the car properly diagnosed before you waste money on a new cat.

shamu2new

Many Thanks Nissan Doctor

I had the diagnostics and an emissions done and thats what the mechanic told me needed doing. He said it could only be the downstream Oxygen sensor or the CAT and seeing as the sensor has already been replaced its likely the CAT.

It appears that the problem originated over a year ago when the coil pack went and dumped pure fuel into the system. Im told that this affected the sensors and now the CAT. Just worried on how much a CAT is going to cost then is it likely to go again. Should I try and get rid of it and go up a couple of years or fix it and hope for best? Just looking for ideas really.

Gandr

i have a very similar prob with a 2litre Zafira.i left it with a mechanic yesterday and he reckons its a electronic problem with the throttle pedal.apparently its a general fault with the passat and some opel models.im getting the new part fitted tomoro,E210 in Newry,E240 in Monaghan......hope it works.

shamu2new

What kind of fault?

Gandr

im having the same problem with my Zafira.the mechanic first thought it was a manifold filter,but now he says its the trottle pedal.hes fitting it tomoro,we"ll see then.when the mgt light stayed on i was getting no power in the low gears,in top gear i got 60 mph max with my foot to the floor.then the light would go off and all would be back to normal.very scary at times,esp on the motorway.

Nissan doctor

shamu2new wrote: »

Many Thanks Nissan Doctor

I had the diagnostics and an emissions done and thats what the mechanic told me needed doing. He said it could only be the downstream Oxygen sensor or the CAT and seeing as the sensor has already been replaced its likely the CAT.

It appears that the problem originated over a year ago when the coil pack went and dumped pure fuel into the system. Im told that this affected the sensors and now the CAT. Just worried on how much a CAT is going to cost then is it likely to go again. Should I try and get rid of it and go up a couple of years or fix it and hope for best? Just looking for ideas really.

That sounds like a reasonable diagnostic conclusion TBH. If the original cause of the problem(failed coilpack) has been rectified then there is no reason for the new cat to fail prematurely.

shamu2new

Any idea of how much a CAT supply and fit should cost me?

Nissan doctor

shamu2new wrote: »

Any idea of how much a CAT supply and fit should cost me?

Off the top of my head I'd say anything from €150 is for a cheap universal cat to maybe €300-€350 for a good quality direct fit part.