R33 Gtst S2 Running Rough - Help Needed!

[01kings10]

Lately my R33 GTST S2 has been running really rough, the car 'vibrates' while idling and under throttle the shake gets worse, as if the car is missing.

Also if I give the car a small rev at idle, the idle screws up and fluctuates better 100-800rpm. I can correct this by free revving the car to about 3k RPM???

Since I bought the car 3 months ago it seems as it has lost a fair bit of power throughout the rev range due to these problems.

The story behind it:

I installed a powerFC in the car which had a tune for another car, I ran this for about a week then took it out because the car was running too rough (the car was running very smooth with the stock ECU). This is where the problems started!

After putting the stock ECU back in I found that these problems continued, and the car is still running rough.

So far to try and fix the problem (thinking it was a simple misfire problem) I've replaced the spark plugs with platinum and reset the ECU, but no luck

Some info on the car:

• RB25DET 140,000km
• New platinum plugs
• New Walbro 255lph fuel pump
• FMIC
• 9psi boost
• Pod filter
• 3" turbo back exhaust

Would really appreciate any sort of help!

Thanks

[markdem]

get yourself a nice little - slow but sure - process of elimination going. i'd be looking at:

connections (this includes pipes: air leaks)

timing

fuel systems

start simple, then get more technical

Edited November 17, 2011 by markdem

[Nanogrip]

Try cleaning out the idle air control valve. Easy work and there is a very detailed thread about it somewhere in the forums. Check it out as part of your process of elimination as suggested by markdem