LC Running Like Bag of Nails

[mattgcupra]

Evening all,

My LC idles fine but sounds like a bag of nails when accellerating or when putting on more revs. Crusing at 70 isn't any different but acceleration power seems down. There are no warning lights on, oil and coolent levels are fine.

A couple of searches indicates that it might be coil pack or MAF sensor or possilbe a boost leak (although it does feel like i've still got boost) but I havn't had a chance to unplug and check anything yet.

I've not got vag com yet but am aware that a couple of tests and plugging in vag com should be my first course of action but I'm wondering whether anyone has had similar symptoms and what the fix was?

Any information would be great.

Cheers

Matt

 

[wisejason]

Coil pack and MAF are both the right places to start looking. If you unplug the MAF the engine light will come on and I think you should limit the test run to a couple of miles.

I'd probably start with putting a request for help in the VAG-COM section, there is bound to be someone in your area willing to help. That should light if there is a misfire or reduced MAF reading.

 

[mattgcupra]

So I started off with my basic testing today.

Left the engine running while disconnecting each coil pack one after another and there was a significant change in running sound. Each had the same affect on engine noise (presumably as it was only running on three cylinders) so I think that's pretty much ruled out a coil pack issue.

Did the same thing with the MAF. Disconnected while the engine was running and there was a slight drop in revs which then came back up (presumably while ECU suddenly doesn't have a reading and then goes to 'soldier on without it mode') but after that the engine was running pretty much exactly the same as before.

Faulty MAFs seem to be a fairly common issue do they tend to always cause the same symptoms or can the same fault affect running in different ways. I've read about MAF cleaning so presumably the affects can vary depending on fault with it/dirtyness.

Does the fact that there is no change suggest a problem with MAF or no problem with MAF??

Yes I know that VAG COM is the only definite way forward but I'm after opinions and previous experiences.

Cheers

Matt

 

[wisejason]

I've never actually encountered this problem - you'll have to hope a more informed SCN'er picks up the thread...

Did you drive the car with the MAF unplugged?

 

[mattgcupra]

Thanks for the input.

Yeah drove for a mile or so then unplugged the MAF and drove the same mile back and there was no change at all appart from the odd hesitation at idle.

The 'running like a bag of nails' almost sounds like the timing is out and a bit of reading suggests that MAF sensor will influence fueling, ignition timing etc so I think that I might head over to Euro Car Parts tomorrow and replace it. I do so many miles at the moment that I'm a bit worried that I'm going to wreck the CAT but I suppose that if that does happen it'd be a good excuse for an upgrade.

I've read a couple of threads which seem to also indicate that a dodgy lambda probe could throw up the same kind of running problems.

The more I think about it the more I'm convinced that it's sensor related but there are no error lights.

Has anyone had faulty MAF or Lambda sensor with no warning lights in the car?

CHeers

Matt

 

[mattgcupra]

New MAF installed in the carpark at lunchtime. A quick start up afterwards sounded promising but I've disconnected the battery for an ECU reset. Will give a proper update later.

 

[mattgcupra]

New MAF has not solved the problem. Ordered a VAG COM cable and will check for error codes. I should have done that to start with really. Oh well.

 

[greesha]

Sounds a bit like the problem i have. Car is still quick but im sure something is wrong because it doesnt pull like it used to in 3rd gear and above. I will try to do some logging as soon as i can to check whats wrong ;<. When i plug it into vag com it gives me fault code with a boost leak between DV and Turbo (Lee69 already told me to check all vacum pipes and breathers but its sounds like quite a challenge for me).