hi all,
i have a 95 sti and its developed a splutter at top revs, i have checked the:-
coils
changed the spark plugs
cam sensor
crank sensor
checked for ecu code (all clear)
reset the ecu
what else could it be?
i have a front mount i/c
apexi induction
full stainless
all these have been on the car since i got it 3 years ago but its now got this problem, any help would be nice, thanks.

 

by top revs you mean what number....

 

around 5k on flooring it.
ive just cleaned out the boost solenoid and it seems a bit better but still there slightley, can i clean the map sensor with brake fluid too?

 

no idea! carb cleaner might be ok,not sure on brake fluid.

 

Brake/clutch cleaner isn't it? Carb cleaner would do too I think. Prob all good stuff, much of a muchness.

Wouldn't use brake fluid - it'll be sticky and wont evaporate. The other fluids mentioned run the dirt off and also evaporate away...

 

How have you checked coils?

 

+1 ^^^

Top end of the rev range hesitations more often than not to do with the ignition system braking down in some way.

 

i changed the spark plugs once and one was faulty, so it does happen with a new set. could be those?

 

tww, it's hard to check the coilpacks visually (micro fractures can short out).

I'd try to get hold of a known working coilpack and swap it in for each of your ones in turn, and go for a test drive after each change. That might pinpoint any misfiring ones...

 

You cant swap one about as it is often more than one at fault

Replace then and you will notice the car much smoother and hopefully this issue resolved

 

Sure.

But I was on about borrowing or buying another fifth one (not swap his four existing ones about). That should hopefully pinpoint the one, or ones, that is/are playing up. Then he could buy more as necessary...

 

all four have seen the same heat cycle, the same temps, and the same nubmer of miles.. if one needed replacing then so do the other 3...

Simon

 

Fair enough. Sound logic.

Indeed, I experienced this myself on my previous WRX. Car failed MOT on CO2 emmisions. Lambda needed replacing, but still failed. Then 2 badly worn coilpacks were replaced (the knackered ones were causing inaudible low rev misfires causing rich mixture), and it passed. Then the other 2 (not so bad, but still same age, as you say) were replaced soon after...

 

hi again, thanks for all the advise, i did check the coils but as you said there could be real small cracks, ill change them for another set off my impreza based rs200, i know they are all good so will solve weather its the coils or not, thanks again, ill let you know.

 

Yeah, keep us informed...

 

well well well, after i checked the pesky coils it turns out it was them after all, there must be something wrong with one that cant be seen by the human eye, its a different car now, a massive thankyou very much for suggesting i look and changed them,
how can you check the coils when there doesnt seem to be anything wrong?

 

It's the way electrics works unfortunately. It only take a microscopic fracture for the spark to arc to it.

Can never rely on a cursory check with just the naked eye.

So is the car running perfectly now, then?

 

oh yes perfectly, i am more than pleased with it, thanks very much for everything, im sure ill be needing your expertees again, all the best, phil.

 

Glad you're all sorted.