edgy

OK, here is the dealio


Fairly recently, I started noticing a problem on hard acceleration with my IS as most of you know I am .net OG and still have a custom supercharged/supra TT block-GE head/GS400 TB motor.. has been runnng awesome for 4+ years the motor has been perfect, only problems I have had recently is some down time with my SC after popping a belt finally last year after 2+ years of abuse....

I drive alot in traffic and still drive the car almost daily, when I am hard on it i kept feeling like the Rev limiter was kicking in early.... when i finally paid close attn to the gauges etc i noticed that:

1 - it happend regularly at just over 4500 rpm.....

2 - it happens ONLY if i am pushing the gas pedal past 50% throttle
(IE : if i am at half throttle, accelerating steadily but not aggerssively
the car will run steady thru 4500rpm to redline and NOT misfire/cut out.)

3 - it feels like the typical rev limiter/cut out, or like Ignition is misfiring badly
pretty much like i lost a Cyl.

4 - misfire/cutout happens in any gear if I rev. hard thru 4500 rpm

5 - when I felt it originally, I always lifted immediately & shifted assuming I
hit the rev limiter...but i began to feel like " damn that seemed to hit
early" .... & I have had NO CE LIGHTS in this time. other than the hi-rpm
issue the car starts & runs normally nothing strange.

6 - In testing this recently I kept my foot down for a second
or two after i felt the misfire and BAM!!! ...CE lights galore,.. can't
remember all the codes....but when I looked them up it was basically:
- Evap. Emissions Sys. problem, - PCV valve, Charcoal canister issue etc.
- O2 sensor problems B1-S2 failure + B2 S2 failure...

7 - all CE ligts clear when i reset the ECU by killing power and they do not
come back again unless i hold my foot down again for a second after the
misfire/cutout hits at 4500PM, then they all come back again. If driving
normally & not hard, I do not get any CE lights at all.


I have checked for Vacuum/ boost leaks after the MAF sensor thru my entire intake system etc and i found nothing, the AF ratios when this hits are in the 12. range...nothing abnormal based on how it was running before this problem arose.

I have replaced the MAF sensor with a brand new one, no improvement


FYI... i am still running the I manage electronic fuel pressure management to add fuel under boost & from what i can tel lit is working perefectly as usual. I am also running an HKS DLI ignition systemr And a Turbo XS ignition amplifier. i ran them both as a test after i got the HKS to see what happened and i noticed no problem so I left them both in they connect to the ECU totally differently so i was curious if they woudl complement each other or cause a problem... the Turbo XS connects to the ECU harness untder the ECU cover while the HKS connects to the Ignitor leads right in the engine bay... i have run the car like thsi for almost 3 years....with no problem. ( and no discernable improvement either...) I am planning on pulling out the Turbo XS unit and selling it as i think the HKS is fine for my needs on its own.


Because it is a hi rpm over 50% throttle only issue i have a concern that it could be VVTI related... / or some kind of fuel problem...? Ignition problem?

Obviously,...I am at a loss.....


Finances are tight as a **** still and i really need to try and troubleshoot this as far as i can go on my own before i have to bite the bullet & pay some one to help me figure it out... So as many things as I can check off the list as possible causes for this pain in the *** problem will be a big help to keeping the cost of this repair affordable for me.


I appreciate Any help or advice you guys can offer, so many of you guys here have much more extensive knowledge than i i defer to your collective genius

Help!



Ed G.



......Still kickin, Still boostin' & bustin my **** to keep my head above the water line.......barely