lumpy acceleration and idling :(

[cus]

i have a mk3 ibiza cupra and i'm getting the following problem..

i have lumpy idle, but only when changing down gear and coming to a stop.
also its lumpy when accelerating, but okay if driving slowly (still a tiny bit rough though)
just had a coil go on me last week.
only error code on vag-com was to do with my cambelt (getting sorted this weekend)

could the cambelt be causing my issues,even though the error code has been there for months and months?

also just moved my maf sensor closer to the air filter, should i try moving this back?

i've done a throttle body alignment as well.

should i check my coilpacks and spark plugs and make sure they are all seated okay?

oh, btw, it was okay for the first couple of days after getting my coilpack replaced.
i'm confused #

could this be signs of another coilpack going?
maf going?

 

[Damoegan]

Could be the MAF mate. Quite often when one coil pack goes another will follow soon after so it could be another coil pack.

 

[cus]

cheers. no faults are getting picked up on vag-com.. but is it common not to appear?

i'll move my MAF sensor back again and see if it makes any difference. i'll also rerun vag-com tonight and see if it picks anything new up

 

[Damoegan]

vag-com wont pick up a dieing coil pack of MAF, only if it has died.

Try unpluging the electrical connector on the MAF and see how it drives. If it drives better then you need a new MAF.

 

[cus]

i'll try that as well. thanks for the quick replies!

 

[RichFred]

Yeah I agree, but I'd wait and see if the cabmbelt is causing it, once it's done, and the codes have been cleared, if your problem persists i'd go for (in order of expensiveness!) coolant temp sensor, that usually only causes problems when it's not warmed up properly, e.g. crap cold starting etc, but it's not unknown for it to cause shitty running generally. Then the coil packs and/or your MAF, have you tried disconnecting it?

 

[cus]

Yeah I agree, but I'd wait and see if the cabmbelt is causing it, once it's done, and the codes have been cleared, if your problem persists i'd go for (in order of expensiveness!) coolant temp sensor, that usually only causes problems when it's not warmed up properly, e.g. crap cold starting etc, but it's not unknown for it to cause shitty running generally. Then the coil packs and/or your MAF, have you tried disconnecting it?

1. gonna disconnect it once i leave work and see if it makes a difference.

its fine on cold starts, so thing the coolant temp sensor is doing its job.

2. will move my maf back so that it sits next to the TIP and not the air filter (as it was like that before the problems occured)

3. gonna run vag-com again and double check for codes.

4. should i then test the 3 coilpacks that haven't been replaced? i have a spare one anyway.

does that sound like a good order to do things in??

 

[Damoegan]

I'd start by doing the MAF test mate.
Then if you have a spair coil pack I'd use that and swop it with the other 3 older ones one at a time and take it for a test drive. If its a failing coil pack you should then be able to eliminate the faulty one.

 

[cus]

I'd start by doing the MAF test mate.
Then if you have a spair coil pack I'd use that and swop it with the other 3 older ones one at a time and take it for a test drive. If its a failing coil pack you should then be able to eliminate the faulty one.

never thought of doing that. i'd definately prefer this then pulling them out one by one!

cheers, very helpful

 

[-pseudonymous-]

You could try logging blocks 014 and 015 in Vag-Com on idle. This should give you a missfire count on each cylinder which may also give you idea if a particular coil is faulty. But coil packs tend to play up under load so Damoegans method might be worth a try.

As above Vag-com will only throw a fault code if the maf is fried, not if its just a little poorly. You can try disconnecting it to see if it improves but probably best off logging block 002 to see if its reading healthily.

 

[cus]

i dont have a registered version of vag-com. so cant log anything. but i'll try the steps above and i'll see what happens

at least i have a list of things to check!

 

[-pseudonymous-]

Oh right, didnt realise you didnt have the full registered version although im pretty sure you can still log measuring blocks 001 to 025 in the engine module so you should be ok.... worth a try.

Good Luck.

 

[cus]

disconnected my maf and everything seemed to run a lot better. pretty much perfect i'd say.. apart from one funny thing.

i boost hard to make sure i got fully boost still and it usually goes to 18psi.. it hit over 20psi before i took my foot off!

thought it must be the gauge just bouncing up too quickly.

reconnected my maf, whilst driving home put my foot down again and it hit 25psi and then limp mode.
i've checked all hoses for splits, checked intercooler pipes, everything.

any reason why it would do this? vag-com is out of the question as i cant find me cable. i know its a guessing game, but any ideas? my n75 is clamped in place fine, but iguess it might be that? help lol

 

[Damoegan]

Could be a failing dv. I had a problem with a Bailey DV30 where it stuck in the open position so could not dump the boost. Is there anyone close to you that you could try there dv? or do you have the standard dv try that.

Just a though mate.

 

[cus]

so if its failing and in the opening position the boost would increase and not stop?

 

[cus]

well.. moved my MAF back to the TIP, before my elbow join.. and its working fine now! lol.
hopefully i haven't spoke too soon, but its idling fine and pulling fine. i'm just not gonna boost high for a while until i have chance to check my dumpvalve.

its an AMD Turbo Dynamics one, anyone know if you can get a repair/service kit for these??

 

[dogsxxx]

ive had a similar problem,if your dv is failing it either showed up as 'boost pressure valve malfunction'or 'turbo to dv pressure drop',i replaced the dv with a oem till the forge comes and it cleared my faults.The other thing i did today cos my idle was lumpty and felt like it was misfiring was cleaed the throttle body...got some carb cleane,cleaned it then put some injector cleaner in petrol tank...reset the tb in vagcom and now idles alot smoother