Whats causing this?!

[Dan_the_man]

My cupra has started having a few issues.

When I start it up, the idle is lumpy. It goes between 800rmp and 1000rpm and the needle moves up and down, then might settle for a bit and there is a slight misfire every now and then.

Sometimes if left at idle the needle will rise to 1000rpm and just idle like that?

What should I be checking first?
The car is due a service so could it just need some new spark plugs? or could it be the MAF on the way out?

Thanks

 

[Kevgrady]

Check the MAF, unplug it and go for a run see if it improves, if it does go get a new one

 

[Dan_the_man]

The car runs fine when im driving though? Its just on idle i notice the issues?

 

[Kevgrady]

Had the same problem and it was the MAF on mine

 

[Rik N.I.]

Have you not tried to diagnose it yet?

 

[Dan_the_man]

I dont have VAG Com. So was just trying to get some ideas really as its booked in to Seat on Fri. Would prefer to sort it myself if possible.

 

[cuprabaz]

For the idle re-align the throttle body and for the misfire check plugs and coil packs. There are a few in depth threads about the throttle body just runa search for it.

 

[Rik N.I.]

Before I got vagcom it only cost me £30 to get seat to put it on their comp then just fixed the problems myself

 

[JIMYU]

i could be something as simple as the coolant temp sender,,,this can cause strange idle sometimes

 

[RichN]

i could be something as simple as the coolant temp sender,,,this can cause strange idle sometimes

YUP I agree with this, mine was all over the place, anywhere between 800 and 4k rpm.

Get somebody (not Seat!) to run VagCom on it, see what it's logged and go from there.

 

[JIMYU]

seat have never charged me to do a fault code print out...it takes all of 2 minutes! my local revo dealer are also happy to do it (and I don't even have revo). Being polite and friendly will get you far

 

[GeorgeF]

as jimyu said just run it down seat and get erm to plug there comp in. i work for vw and we dont charge. could be loads of things though. throttle body clean and basic settings is a common for 1.8T's, maf sensor, coolant temp sensor so before u go bolting bits on see if she has in faults in her.

 

[Dan_the_man]

UPDATE - Thanks for the replies, well it got worse today. Noticed that the idle had got worse and also on the little cpu that tells you how many miles of petrol you have left was very innacurate, i.e I put in 10 quid and it said 30 miles left!

Whilst driving home the misfire started to get worse, so i pulled over. Then it wouldnt start, lights on dash flashing like mad.
So i suspected the ECU (my last one filled with water), so i took it out, opened it up and left it for 5 mins. Screwed back together and it started first time, and drove all the way home fine?

So could I have another damaged ECU? although there were no visable signs of water? Confused!

 

[goble]

or the mulitiplugs for the ecu have corossion in them and causing poor connections

 

[GeorgeF]

would have thought there would have been signs of water if it got in there. infact i know there would be. wat did u unplug the ecu? mite have resealed a poor resistive terminal. if u unplugged the ecu mite have reset sumin. best to pop down ur local dealer and get erm to plug their comp in. bets to be safe than sorry

 

[StanTheMan]

Fill every connector with dielectric grease, cover the ecu internals in the stuff. You'll never have a problem again.

 

[Dan_the_man]

car went on diagnostics at SEAT... Lots of totally random faults.

none of which pointed to anything specific, this is exactly what happened last time when water got in!

Some of the codes were turbo related ie overboost, Nsomething valve, one of them side nearside indicator lamp intermittent failure or something!

How are forge coming on with the ECU cover? I need one asap!