in a mornin wen started my 94 wrx sti seems to run rough like its its reluctent to rev over 2000rpm then it will rev over ok this only lasts about 5 mins untill warm also noticed that revs stick to about 1700 rpm from time to time any ideas ? its driving me mad. cheers lads and lasses.

 

coil packs at a guess..

if you run an extra earth wire between neg battery terminal and engine it might improve for a bit.. but best to replace coil packs anyway if never been replaced as they break down over time internally.

 

any idea how much 4 coil packs will cost me ? ? cheers

 

£200~250.

As Performance were selling them at a good price.

Simon

 

I think that the engine is lean during the warm up. Confirm that by insatlling an A/F meter. It should be below 13:1 when cold and increasing towards 14.7:1 when the engine has reached 80 degrees.
Have your injectors cleaned and if the problem is still there install a fuel pressure regulator and increase the prssure by 0.3-0.5 bar.
This has nothing to do with the coil packs since if they were the problem, the engine would missfire in full throttle.

 

You are suggesting that if there is a problem with the fuelling rather than checking it he fits an adjustable fuel pressure regualtor and increases the fuel pressure.. nothing like solving the symthom rather than the cause.
Nothing to say for screwing up the overal fuelling map.

It won't misfire on boost with faulty coil packs unless he is running over standard boost.

You can check the coil pack theory by reducing the spark plug gaps.

Simon

 

I did not say go and install a fpr. I said confirm that it is lean with an A/F meter first and before installing the fpr, i said clean your injectors.
Read more carefully.
Most probably since it is lean at idle, it will be lean through out the entire map and when increasing the fuel pressure, you will do it with the A/F on.


This is a common problem among those older models. The fuel pumps start to loose some ability, the injectors get dirty etc.
I suggested the least expensive solutions.

I did not mean to offence your opinion, but my experience with these models suggests that the failure of coil packs does not only affect the idle but gives more problems and since this car is ok when warmed up, then it shouldn't be the coil packs.

 

if fuel pump is weak then it will show up as a problem when warm too..

idle uses less fuel than on boost, even when enrichment is applied.

seen injectors with over 150k on them with no problems..

possible an injector has failed though..

I am still inclined to think coil packs.

Simon

 

Here we clean injectors every year and almost always seem to have some dirt. Ok, I suggest you clean the injectors but remove them from the engine and take them to a specialist and have them cleaned and checked and have new o-rings installed. This costs a fraction of byuing new coils. If the problem insists, try the coils that Simon suggests.

 

ok stavros and simon cheers guys yer the car is fine under throttle revs rite up ok runnin standard boost i think just under 1 bar according to standard sti gauge could be wro ng tho as ive heard these gauges arent that acurate ill try the cheapest 1st and see wat comes of it.cheers guys