problem spluttering at high revs

[nip]

sod that then, anyone got any coils i could test please

[JP]

I 've just read this thread and by pure chance I was going to ask something similar. A little background on mine along with problem and findings.

First of all I'm running a 10v Turbo on Kjet. What I found was when under full load from around 4000rpm I get quite harsh stuttering/misfiring. So I figured I'd systematically work through. I've done the zener diode mod first of all incase it was the fuel pump cutting out. No difference.
Next it became less frequent and less pronounced by fitting an electronic boost controller as it eliminated rapid rise of boost and over excessive spiking. Which was when the issue was most pronounced.
However the problem still persisted so I figured I may be running lean so I added a 5th injector (or 6th in this case). Again the car pulled smoother but under full load it still persisted.
Except when the engine was cold ?!?! Rather strange I thought and then figured when the engine is cold I got a higher fuel pressure as it is a kjet so maybe the 5th injector wasn't upto the job?.
ok so next I fitted a wideband data logger. Under full load at 17psi it was holding fine at 11.5:1 afr if fed in gradual with no stuttering. However if I floored it the afr dropped to 10.6:1 and the misfiring/hesitation occurred.
This led me to the conclusion that the issue isn't fueling but quite clearly spark. A change of leads and coil has not resolved it nor a fresh set of plugs.
This however where the issue lies the plugs. From experience running 9sec v8's with nitrous trackside we used to have similar issues where the increased combustion temperatures and pressures of nitrous or forced induction caused problems with the spark jumping the plug gap (in effect you blow out the ignition spark). This was resolved in 2 ways. #1 was to lessen the spark plug gap in 2 thou increments until the desired result was achieved. This worked in conjunction with dropping a heat range on the plug to stop predetonation. #2 solution was to uprate the coil to a high voltage one to aid the spark in jumping the gap.
I feel that your misfire is the result of the spark plug type and gap. Which is the same conclusion I have come to on mine.
This however is where I was going to ask the following. Which is which spark plug do people run on the tuned 10v's? As all the literature I read people say my symptons come from running single groundstrap plugs and you are best of sticking with the standard 3prong ones. However it has come to my attention they appear not to be upto the job.
For your engine I would start by looking at which is the best plug and gap for your application and see if this resolves your issue.
HTH JP

[nip]

thanks RWD ive recently changed the plugs , i know the coil boots r knackered, i think what im gonna do is swap them around

[dest]

When on full boost, does it feel like the car is jerking on and off the boost quickly?
Mine is doing the same, Ive got a nasty feeling that its going to need new coil packs

[nip]

yes dest thats exactly whats its like, have u checked the coil boots matey

[dest]

Yes, when the plugs were changed I noticed a couple of them looked abit worse for wear!
Would changing just those make much difference though?

[nip]

yes i been told so , but i cant really see it myself, mine does it when hot

[dest]

As already mentioned, it seems daft to buy new boots when the coils come with them, but the cost is alot different!
Is it worth the risk of buying new boots and hoping it sorts it, or take the plunge...

Mine seems to pull better when colder too (not that I make a habit of it, just to check)

[nip]

lol , thats where im stuck , what would be a good remidy is swap coils from say urs to mine and see if there is any difference

[PeteRR]

A swap-and-see would be ideal. But if the coils are the originals, and/or have 100K+ miles on them, it would probably be as well to change them all anyway. Especially if your keeping the car for any length of time.

You could also go for the 1.8T coil conversion which is cheaper than the O.E. set-up. (and includes the POS's).

[nip]

thanks pete, how does the 1.8t conversion work, also how easy is it to swop, just phoned up my mate can get coil packs for 300 quid for s2

[PeteRR]

The 1.8T conversion from 034 comes complete with a loom. I gather it's just a case of removing your old coil cover (complete with old coils) fit the new coils in the plug recesses, plug in the loom and that's about it. (leaving your old coil cover off).

I may go this route myself. You'll find lot's of discussion on here about them if you do a search for '1.8T coils' or 'coil conversion' etc.

[nip]

ok cheers pete il look into this was hoping to leave the coil cover on tho

[Jamo]

Dont do the 1.8T conversion it's false economy! They don't like heat and the S2 engine bay fries they.

If in doubt speak to Carl Avant Nip.

Also could be the POS at fault. I don't know how you check them though.

[Jamo]

Dont do the 1.8T conversion it's false economy! They don't like heat and the S2 engine bay fries they.

If in doubt speak to Carl Avant Nip.

Also could be the POS at fault. I don't know how you check them though.

Consider this S2 coils need change once every 10 years the 1.8T can fail withing 6 months to 2 years. They have already gone past the J suffix release as they continually fail and VAG have to keep releasing new improved versions.