S3 stuttering, then fine after coil change, then stuttering again.

[sje00]

So My brothers S3 with Beach buggy hybrid is having some problems.

We had it mapped by Badger5 but only got to 280bhp due to the wrong spring in the actuator (too weak)

We drove it home ok. But a day or two afterwards it developed a nasty hesitation at 3000rpm. So my brother replaced a Coil and it dissapeared.....until the next day. Where the stutter was backl with vengence!

It now happens all over the rev range when a decent amount of throttle is applied.
He changed to 2 oldest coils yesterday and the problem disappeared. For a few hours of mixed driving, it was fine. But its back now.
He has a brand new Fuel pump to go in.

But we are unsure of the:

1. What is causing this?
2. Why when we changed the coil packs it stopped doing it then returned?

Any ideas??

 

[Kodak]

have you changed the spark plugs and gapped them to 0.7mm might be worth ago or you could go with the 2.0 tsfi coil packs and set the gap to 1mm I believe

 

[sje00]

when the engine got rebuilt with forged rods and new rings and bearings etc it had new plugs.

i personally am unaware of the gap.

 

[dre_S3]

Have you checked the wiring that goes to the coils more or likely cracked and showing bare wire ?

 

[Westy]

Could be more then just 1 coil pack. If you don't know the history of all 4 coils I'd change all of them for genuine ones. A remap will always highlight weak coil packs.

Also as Dre said, it could be the coil pack wiring.

Best thing to do would be to find someone with VCDS/Vagcom and scan it. If its a coil pack you'll have an error pointing to a misfire on a specific cylinder. You move the coil pack from that cylinder to another, clear the code and then see I the error follows the suspect coil pack.

 

[badger5]

Are you swapping old cold for other old coils?

New coils and all 4 are what I would be fitting and a new set of plugs, gapped 0.7mm, so ign system can be deemed as good as it can be.
Whether its an ign only issue or fueling (lean misfire) the afr's would need to be seen to judge if its leaning out causing misfire and the fuel pump and sustained pressure is ok or not.

Have you fitted the correct actuator spring yet?
440's on the hybrid not really adequate without a 4bar fpr, but doable if the pumps delivering the 4bar + boost sustained. (550's the injectors of choice for this application) and actuator of 12-15psi to stop it from being blown open.

 

[badger5]

AEM Wideband is suggested so you can see what your narrowband ecu is actually up to..
AEM 30-4100 DIGITAL WIDEBAND UEGO O2 AIR FUEL RATIO CONTROLLER FREE UK SHIPPING | eBay

Well worth it to keep an eye on things, as lean and boost = disaster potential

Narrow band ecu cannot make fueling changes to compensate for fueling issues under boost/wot....

 

[sje00]

all the coilpacks have been replaced recently now.

The spring hsn't been changed yet. We wanted to sort this issue first, then proceed with further mapping.

 

[badger5]

checking afr/fuel pressure is key tests

 

[Kodak]

how did you get on with this was just interested to see if you got to the bottom of this

 

[sje00]

I suggested to brad to whip the plugs out and check the gap size. At the time of asking he had already put the old plugs back in and funny enough, its absolutley fine! no hesitations at all now. so he's got some brand new never been used plugs, that i'm going to gap for him and we'll try these in time for the rest of the mapping to occur, once the actuator spring has been swapped.
Hopefully, further mapping turns the car into the animal it should be. Get some more mid range and top end out of the ******!