Misfire when cold

[scrote]

Hi folks. Can anyone give me any advice on a problem i've had over the last few weeks? I've got a Cupra 20VT (not R) and when the weather is cold I sometimes get a terrible misfire and erratic idle speed on start-up. It can last for a few seconds to a couple of minutes and then things are fine. I've had it in to my local VW dealer but they found nothing on the diagnostic as it wasn't doing it when they had it in. Anybody had anything similar or heard of this problem before?

 

[Gezz]

It depends what you mean by misfire, my car stuttered like it was going to stall when cold and no power in 2nd but seemed fine in higher gears. once warmed up it was fine,

That was my MAF, once changed its been fine.

 

[scrote]

This is similar as it seems to be worse as soon as it's put in gear. The revs drop right down but it never actually stalls.

I guess I could try disconnecting the MAF when it does this to see if the stuttering stops.

It's frustrating because it's intermittent and by the time I get out and get the bonnet up it's normally stopped.

 

[MrJohnnyB]

Sounds similar to what i have... try unplugging the maf and then starting the car and see if you get a reoccurance of the issue, if you dont then it's the maf. Doing this will turn on the epc light, however if you leave it plugged in for a while it will go back off.

Additionally have you tried cleaning the throttle body? It kinda sounds like the symptoms of a dirty throttle body, but that said normally this wouldnt stop after a few mins....

 

[scrote]

I've thought about the throttle body but as you say if it was dirty or obstructed i'd expect to have problems all the time not just start-up.

How much does a new MAF cost as it seems to be the cause of a lot of issues if it's playing up? It may be worth replacing just to be on the safe side. I've only recently had the car so don't really know it's history apart from it has a FSH.

 

[MrJohnnyB]

You can get one from GSF car parts for £43 i believe (www.GSFCarparts.co.uk) same as europarts (the site is currently down!). Stealers charge 67... Thanks to CupraKev for that info that i jsut stole and took the credit for!

 

[scrote]

Thanks for that. Think i'll change it and see what happens.

I'll keep you posted.

 

[stewbie55]

Thanks for that. Think i'll change it and see what happens.

I'll keep you posted.

Let us know how you get on as I have exactly the same probelem at the moment. Only does it when cold in the morning and dies (but doesn't stall) as I try to pull away, but very intermittent.

I assumed mine was a coilpack as it sounds like a genuine misfire, but haven't run a diagnostics check yet.

Maybe I should try unplugging the MAF in the morning before starting it to see if it cures the problem??

 

[traumapat]

I've thought about the throttle body but as you say if it was dirty or obstructed i'd expect to have problems all the time not just start-up.

How much does a new MAF cost as it seems to be the cause of a lot of issues if it's playing up? It may be worth replacing just to be on the safe side. I've only recently had the car so don't really know it's history apart from it has a FSH.

the gunk in the throttle body could be rock hard 1st thing... id check it anyway.
what exactly does the rev needle do when at idle?
i had a cold start issue where needle would move back and forth +/- 200rpm. seemed to clear just after cold start cycle usually. it was cured by packing dielectric grease in the maf connector... have a search on here for dielectric
in my case moist air was causing an arching in the connection.

 

[DPJ]

You can get one from GSF car parts for £43 i believe (www.GSFCarparts.co.uk) same as europarts (the site is currently down!). Stealers charge 67... Thanks to CupraKev for that info that i jsut stole and took the credit for!

For goodness sake don't get their cheapest MAF - get the genuine Bosch one.

 

[traumapat]

For goodness sake don't get their cheapest MAF - get the genuine Bosch one.

agreed. dealer for mine. might be 20 quid more but at least im confident it does what its sposed to. its not worth the hassel and doubts.

 

[DPJ]

agreed. dealer for mine. might be 20 quid more but at least im confident it does what its sposed to. its not worth the hassel and doubts.

You can get Genuine Bosch ones from Euro Car Parts and GSF - come better packaged than the dealer supplied ones.

 

[traumapat]

You can get Genuine Bosch ones from Euro Car Parts and GSF - come better packaged than the dealer supplied ones.

yes but i get coffee and 10% as the guy thinks i own a garage

 

[scrote]

Traumapat - the revs do similar thing when it's playing up, dropping from 900 to about 500 very briefly as though it's about to stall but never does. That's a good call about the MAF connector arcing as it would explain why it only does it when cold/wet.

To everyone else I appreciate the advice about getting a genuine replacement part to ensure reliability - i'll price one up locally.

Thanks again for eveyone's input.

 

[traumapat]

Traumapat - the revs do similar thing when it's playing up, dropping from 900 to about 500 very briefly as though it's about to stall but never does. That's a good call about the MAF connector arcing as it would explain why it only does it when cold/wet.

To everyone else I appreciate the advice about getting a genuine replacement part to ensure reliability - i'll price one up locally.

Thanks again for eveyone's input.

my thinking was the same... logged the maf at idle one morning and the figures were all over the place until a min after it had settled from the auto choke.. by then i think it had burnt any moisture off.
you can get the grease from various places including ebay... 2.99 a tube ish. it didnt cure instantly but improved over 4 days until perfect.

 

[stewbie55]

Well I unplugged my MAF today before starting and no idling problems.

Do I try the cleaning / greasing approach or just buy a new MAF

 

[Feel]

Could be the things as mention, could also be the coolant temp sensor making run rich - do you have a green top one?

Also, I've had intermittent misfires when a coilpack is on it's way out - odd misfire when cold, then later "full" duff coilpack symptoms until the car wamred up, then later still the coilpack goes.

 

[SimmoCupra]

Mine's doing exactly this. I've just removed and cleaned the MAF sensor. (in me lunchbreak). It seemed a little better, although I can still feel it stutter.

Time to bite the bullet and buy a new MAF...?!??

BTW - when it is stuttering it does sound like the dump valve has lifted and is dumping through the intake. Or the N75 valve has opened? (Can hear it in the passenger footwell kind of noise.) (007P DV and Green filter).

 

[SimmoCupra]

So, After cleaning once the engine was coming of its cold start enrichment there was chattering noise coming from the engine (just idling) (Possible wastegate??) then stopped after a throttle blip..

So, Just disconnected the MAF when I got home. And all seems much better! New MAF time methinks..

 

[scrote]

Managed to get the bonnet up at the weekend while it was running rough. Disconnected the MAF and hey presto! it ran fine.

Going to try the dielectric grease trick first (just awaiting delivery). If this doesn't work then i'll fit a new MAF.