RB20 stuttering...

[240luvr]

Hey guys, I swear I've seen this topic covered before but I failed in finding it in my search... if you know where it is, link me up to it and call me an idiot haha.

I have an RB20DET in my S13, it has an RB25 turbo, TurboXS manual boost controller, SAFC for the tune, upgraded ECU, Walboro 255, Coil packs eliminated, FMIC, 3" turbo back...

now for the problem at hand... When running the car hard and WOT, I get this weird stuttering/surging between 4 and 5k... like I hit full boost (14-15psi) at 3400, then the boost gauge like vibrates between 13 and 15 and I loose power and you can feel the vibration through the entire car, then around 5k it boosts perfect to 14-15psi again and pulls like crazy all the way to the rev limiter... Doesn't do it in unless trying for full boost.

I've checked the ECU for codes, throws a 55...which last time I checked is all clear. It didn't always do this it just started about a week ago. I had a stock ECU in when it started doing it so I swapped to my upgraded one, and no luck still does it. Tried taking and adding fuel between 4 and 5k through the SAFC and that didn't do anything either.

Lastly, it seems to have happened after I replaced the water pump... possibly has nothing to do with it, but possibly does. Could the CAS not being set just right cause this? I just figure that if the CAS or timing was off it would always run like crap, not just between 4 and 5... Any thoughts will be appreciated.

[Carl H]

change your plugs, they are proly fouled out.if that doesnt help then could be a failing ignitor or lack of proper voltage to the ignition system.

[240luvr]

Thanks for the quick reply I'll try to swap plugs tonight and see what happens.

[240luvr]

Alright, ordered some plugs from a local shop that I used to work at, they'll be here Tuesday, so I took my current ones out and cleaned them up and it helped a lot. So I know when the new plugs come in and I get it re-tuned all will be well.

Thanks again... and from now on I gotta keep it simple.