Cold start/spark plugs query?

[richie777]

Hi,

I was wondering if anyone can help, i have recently brought a 53 leon cupra with 100k on the clock and have started having trouble with starting from cold which has gotten worse over the last couple of days.

I have read through various posts and know there could be a fair few things that it could be, i.e coil packs, temperature sender, spark plugs, MAF, TB but i was wondering if someone has had the same problem and could steer me as to where to start first as i dont get that much time with work and everything to work on the car. Plus i know what i am like and will just change everything for the sake of it.

Scenario - Turning the engine on from cold the revs go to about 1200rpm then after a second or two drops down to about 700rpm and the engine starts to shake and judder before the revs continue to drop before stalling, if i put my foot on the accelerator there is nothing there, it feels dead. (this has got worse the last couple of days). On second start up the revs are fine and it doesnt stall.
Moving over there is a slight juddering of the car until i've driven for about 2 minutes then everything seems okay apart from the occasional power loss for a few miles.
Leaving work at the end of the day everything is fine apart form again the occasional power loss which is why i'm a little confused

I have noticed in the service history that the last service 2k ago the spark plugs were changed, now i'm not too clever on cars so was wondering that if one of the plugs is knackered or that the gap is wrong on them would it be possible for it to cause this problem or am i way off?

Thanks in advance

 

[Jimski]

Initially looking at the problem mate i would lean towards coil packs and a throttle body clean.

However, have you got access to VAGCOM? this may highlight the problem, whereabouts are you?


Jimski

 

[SimmoCupra]

I had this same sort of problem. I spent loads. Plus had lots of people posting with the same sort of problem.

I went through, 2 x MAFs, full set of Coil Packs, spark plugs, and cleaned the throttle body. PLUs did the Maf plug dielectric grease. None of which made a difference.

The only thing I seemed to learn was, When its missfiring (which is what the judder would be) if you can go this with the bonnet up. you can unplug the MAF. This made mine instantly better. BUT this was a new MAF!! What The F~@@...

I didnt have VAG Com, but have had some dealings with ECU's in the past and know that they are adaptive, i.e they will learn.. So, I decided to do an ECU reset, i.e unplugged the battery for 1/2 hour. whilst changing the coolant temperature sensor as well. (as this was my thinking that the ECU thinks the coolant is at some random temperature (-45Deg or something) and applies the IGN and fuel constants to suit. until the cold start enrichment has cleared (which is why the initial revs are higher 1200rpm).

Admittadly the MAF is probably the problem, and will probably not show up a Dash fault code. But unless you reset the ECU after changing something (or could do it with VAG COM) the ECU will have learnt to drive with a knackered MAF, and changing it would have no effect. unless reset.


I'm sure someone will try to correct me, but hey mines working now.. and thats exactly what I did to cure it. (people dont sem to post the cures on here, just the problems. ) hope that helps.

(in short, try unplugging the MAF when its "juddering" , when cold in the morning. and go from there. ) if you search my previous posts. you will probably find the same symptom.

Si

 

[richie777]

Thanks for the quick replies.

I'm in Birmingham mate and dont have Vagcom but was really thinking about purchasing it.
From what i can tell from posts i've read it may very well be worth the £300.

SimmoCupra - sounds like you had a nightmare mate which is why i thought i'd ask on here before going through the same painful process myself, so basically what your saying is that whatever you change the ECU really needs to be reset to make a difference?

Stupid question time - where is the MAF?

 

[richie777]

Just on top of all that, is Vagcom the be all and end all? would it tell me everything i need to know?

 

[SimmoCupra]

have a search on here for MAF's. Its just after the airbox.
As you stand looking at the engine with the bonnet up. Airbox on the righthand side. its the round cylinder thats bolted to it. before the intake goes into the turbo.

 

[AwesomeSarah]

Hi
For what a coolant temp sensor costs , my advice would be check yours , if it is black then replace it anyway
My son got a coolant temp sensor as a prezzie when he first got his MK4 Golf
Then try a throttle clean and reset before going to folk out any moneyon larger items
If the CTS is black , it would not hurt to replace it anyway
The throttle body too , and not expensive for them
Then think about paying for VAG com
Sarah