Engine light and engine stutter

[christii]

So my 2008 GTI Manual has an issue.

The car has its check engine light on. Codes a P0300 - p0304. Multiple misfires on all cylinders.
New plugs, coil packs, upgraded fuel pump.
Car has a K04 kit, Powervalve exhaust, upgraded S3 intercooler.
Tuned 2+ 365bhp.
The car stutters, backfires and shakes at 3500bhp when revving at stand still. Not when driving.
It might of had the issue before the K04 kit and tune because the awful previous owner had the check engine light covered up!
Heading back to the tuner next week but he doesn’t think it’s the map or ECU.
Anyone have a clue what it could be?

[christii]

Also, I’ve ordered another ECU on eBay, when it arrives I might swap them and see if the fault is still there. Or at least give it to the tuning company to try.

[rich83]

Impossible to say with the information provided so far.

Are those the only fault codes?

[GVK]

Has the car been tuned to 2+ previously then got an issue or is it being tuned, only to find an issue?

Have read on here and on the various FB groups about stage 2+ cars breaking the ringlands on the pistons.

Compression test and leakdown required.

[pudding]

Yep, I think I'd be starting with some data logging and then mechanical checks if that all checks out.  A compression / leak down test might not be a bad idea.

[christii]

Impossible to say with the information provided so far.

Are those the only fault codes?

Yes, those are the only codes.

[christii]

Yep, I think I'd be starting with some data logging and then mechanical checks if that all checks out.  A compression / leak down test might not be a bad idea.

I did ask my mechanic to check for a gasket, he assures me it isn’t,  though I’ll double check to see if he did a compression test. Would the stutter be a symptom?

[christii]

Has the car been tuned to 2+ previously then got an issue or is it being tuned, only to find an issue?

Have read on here and on the various FB groups about stage 2+ cars breaking the ringlands on the pistons.

Compression test and leakdown required.

No, the car wasn’t tuned before. Though after the tune is when I noticed the covered up engine light from the previous owner. And then realised the light was on.

[pudding]

Yep, I think I'd be starting with some data logging and then mechanical checks if that all checks out.  A compression / leak down test might not be a bad idea.

I did ask my mechanic to check for a gasket, he assures me it isn’t,  though I’ll double check to see if he did a compression test. Would the stutter be a symptom?

It won't be the head gasket, they never pop on these engines.

Stuttering and back firing etc with no load (revving when stationary) doesn't necessarily point to poor cylinder compression.  It could be sensor / fuel delivery related, so data logging is the next step. If the crank sensor goes, 3500rpm is about your limit in terms of revs, so might be worth checking that.  Does it drive past 3500rpm on the road?  Any hard rev cuts?

[christii]

Yep, I think I'd be starting with some data logging and then mechanical checks if that all checks out.  A compression / leak down test might not be a bad idea.

I did ask my mechanic to check for a gasket, he assures me it isn’t,  though I’ll double check to see if he did a compression test. Would the stutter be a symptom?

It won't be the head gasket, they never pop on these engines.

Stuttering and back firing etc with no load (revving when stationary) doesn't necessarily point to poor cylinder compression.  It could be sensor / fuel delivery related, so data logging is the next step. If the crank sensor goes, 3500rpm is about your limit in terms of revs, so might be worth checking that.  Does it drive past 3500rpm on the road?  Any hard rev cuts?

It drives ok, maybe a slight misfire at idle. Though I noticed it stuttering slightly when engine braking. Anyways it’s currently at Autotune to see if they can find what it is. Fingers crossed they figure it out.

[pudding]

Good stuff.  Please do let us know how it goes as so many people never follow up on problems, leaving 100s of threads unanswered for newbies 

[christii]

Good stuff.  Please do let us know how it goes as so many people never follow up on problems, leaving 100s of threads unanswered for newbies 

Result!!

It was the ECU! Autotune transferred the map onto the new ECU and no more engine light.
The car is driving better as well. No more stutter, and before it was pooping and banging a lot. I thought it was the map but it’s doing it far less now.

 

[pudding]

Interesting! I've not seen an ECU fail on these cars before but anything's possible I guess.  Glad it's back to full health again