TobyZ28

Check out this thread.

I was experiencing the Low RPM Stumble, and I'm so sure that this is the problem now. Anyone out there whos having the LOW RPM STUMBLE should go to their nearest autparts store and borrow a fuel pressure guage, then Check their pressure according to Injuneers helpful comments. I can't believe how far off mine is from stock spec AND how long i went without checking.

This is by far the EASIEST check you can do on your car. Plus, the fuel pressure guage, even if bought can be returned the next day to most stores for a full refund! (thats what im doing =p)

All that is required is hooking up the fuel guage to your fuel rail (unscrew a cap, screw guage on). And then as per the instructions, remove the vaccum line right beside it when its idling and observe the guage then. Took like 10 minutes total. VERY easy stuff. I've narrowed down the problem to my fuel pressure regulator, something in my fuel lines, or the fuel pump now.

Let me be a bit more detailed on my Low RPM stumble problem... Originally I was having a slight slight stumble around 2000k rpm. It got worse over time, sometimes it happesn around 1600 and sometimes as high as 2500 rpm. In the HIGH rpm band it was always fine though. This stumble ONLY happens on light accelleration, say im crusing at 90Km/hr and want to accellerate to 110... it would stumble almost every time. It seems to happen when warm moreso than when cold.

Now over time the car started having power problems at higher rpm. Around 4500+ RPM it would feel downright retarded, like it was missing or hitting a limiter or something. Definatly fuel related. I also just the other day had a code 55 - Lean mixture during accelleration when i scanned it.

ANyhow i had a scanner, scanned the car and at cell 15 and 14 (this is the point where the stumble happens) the Integrators were maxing out at 160 along with the BLM's at 160, for those who arent familar with what that means -> car is reporting a lean condition, if the sensors are working right the cars running very lean and/or not burning the fuel it should. The car is trying to compensate by leaving the injectors open as long as it can!

Hope this helps. I tried to make the "problem" i was having as clear as possible for all those stumblized people out there - haha!

Anyhow im real excited to be this close to fixing it. I'm guessing for me its probably my fuel regulator thats seized up since i can get above 23 PSI... oh please oh please be only the regulator!

Good luck you guys!

P.S. If fixing my fuelpump and replacing the regulator doesnt fix this stumble, i'm going to go on a madd rampage through a park with my baseball bat attacking trees.. erhm.