Car is a 1997 sti3
Simtek ecu,fmic, exhaust with headers, 740cc injectors, 20g turbo, walbro 255
Problem is intermittent...sometimes after driving local and when I park up it seems like it's running on 3 cylinders,only happens when weather is Warmish,
The turbo housing is cracked but didn't think that would be the cause
I have took plugs out and they are fine,leads and coil are fine also...could this be fuel related as sometimes the 255 whines
Thanks in advance
Zak

 

Best thing to do is have a comp test done. Then go from there.

 

If comp was low wouldnt it misfire all the time and not intermittent?

 

Came across a Skyline that was low on comp and funny enough it was running fine. Just felt abit slow.

 

Sh*t man I hope not,it drove perfect today and I did about 10miles lol

 

wtf,,,,,,,,,do a cel code check first

 

nothing wrong with doing a compresion test, im sure the op would have mentioned a cel light flickering on the dash if it had happend

get it checked mate

 

I once tried a cel check code due to spluttering and code came out as maf but I have a simtek so it's mafless
It hasn't flickered at all so didn't think about doing a cel code check...it does drive fine but on the odd few occasions it feels like it's going to cut out

 

hmmm,, the cel check would of found the idle control valve so thats one off the list

 

ICV was taken off couple months ago and cleaned properly

 

you need to get your ecu plugged in by a mapper or by yourself if you have the simtec software. any faults will be logged on the ecu. didnt read you had simtec

 

like you said the comp test does not add up to the symptoms,, this may seem a daft one but when the fans kick in it does tick over lower,, ??

 

nope that bit flew straight over my headlol

 

Not sure about the revs going lower when fans kick in,the revs never normally drop apart from when it's misfiring,I keep thinking it's my fuel pump failing but then again it's a couple months old

 

Did you fit the little filter the right way

 

Yes filter only goes in one way as it has a groove to sit on,I might get a swirl pot setup so might need
Someone kind enough to get me a diagram (picture and writeup preferably)

 

mine was doin the same, we changed plugs, leads coil pack, blah blah, and then the walbro fuel pump, ran fine after that.

 

Sounds like a fuel issue, something like a blocked fuel filter or faulty fuel pressure reg can make it do that and would tie up with the whining pump.

or depending on what the set up on the simtek is, it may be that the closed loop fueling isnt compensating for fuel/air temps or doesnt have closed loop fueling switched on - perhaps faulty o2 sensor. Check the map before buying a new sensor though

 

He is running a Simtek so no CEL fault codes stored.

 

It could be a fuel issue but there are many other things it could be.
The Simtek ECU suffers from electrical interference causing the symptoms you describe. It once took me three weeks to get to the bottom of this on a particular car but since then I have probably come across it half a dozen times and we know what we are looking for.
Your ECU will be locked to whoever mapped it last and we would need access to your ECU by prior agreement to get to the bottom of the problem. This would involve accessing the ECU, coupling up the laptop and then looking to see what is happening. If it is an interference issue we do not need access to the ECU but it is as well to be prepared for all eventualities.
I don't see you say what model year so it could also be a plug lead, coil pack(s) or similar.
We are in a position to look at your car 16 or 17 July in Darlington when Bob Rawle is here for a mapping weekend. We are 110 miles North of Nottingham and I am confident we would get to the bottom of your issues for modest expense if you are still suffering problems.

 

I have had this due to fuel presure issues from a faulty or HOT PFR, sometimes while in traffic the residual heat upset the PFR, I had to move it and move all my fuel lines to. Sort of a heat soak issue.

 

thanks for all replies... i have drove the car everyday for past week and its not missed a single beat
the fuel pump does occasionally whine though,thinking about getting a swirl pot setup,and a 6speed is going in next 2 weeks so will get it mapped again after that and should fin the problem

 

oh yes forgot to mention i dont have a air/temp sensor fitted to my fmic piping,could this be contributing towards the problem as i only notice it when weathers warmish or too cold

 

Yes it certainly could. How come you have a Simtek without having the temperature sensor fitted close to the throttle body on the intercooler hard pipe or silicon joiner?

 

To be honest I haven't had time to fit it or more importantly I needed to get it aluminium welded and don't have anyone to do it,also I have now forgot which wires go on the MAF connection from the air/temp sensor