badssz

OK guys - I REALLY need your help! I am stumped - please read and see if you have any ideas.

I have got my new motor and supercharger in - here is what I have so far....

94 z28 - 6 speed

383 Stroker - Done right
Hooker L/T headers
EGR block offs
52 mm t/b
30# injectors accel
MSD ignition system
AFPR
G-maf - Installed on the Pressure side of the s/c
Vortech S-trim supercharger - with approx 8lbs of boost.
All the other toys that go along with it -

Here is the problem:

At low rpms - or less than 1/4 to 1/2 throttle - it loads up - but if you just crack the throttle a little more 1/2 or more - it runs awesome! If you let it idle, it will eventually kill it's self from overfueling.....I hooked up the scanner and get this - ZERO codes - nothing!!!! All the components that the scanner can read - seem to be doing great. The only thing that I could see that may be a possible concern - was that one 02 was reading like 1200 and the other was like 580. It has not set a Check engine light or anything - so I don't know if that could possibly be the problem or not.

I really don't know where to start - I did check the msd system - disabled it, and re-connected the OE stuff and the the same thing. The only other thing I can think could possibly suspect would be the PCM - I had it tuned, but That is the only other thing I can think would be controlling the air/fuel mixture and making it run poorly.

I am basically ready to jerk this system off the car, and go N/A - I love the supercharger and it runs awesome - but damn - it's been hell to get it right - and I'm still not there.

Please Help me out!

Paul

badssz

Anyone????

Tim240z

What fuel pressure at the rails?

Injuneer

How are you adding the extra fuel for the S/C? Do you have an FMU, or is all fuel pushed through the stock injectors by the PCM? If the latter, who did the programming? How did they address the limits of the 1bar MAP sensor?

If I had to guess, I'd say your MAP reading is too high and the PCM was assuming your are under load, and adding extra fuel.

Under what conditions did the O2 sensors produce the readings you note? I didn't think they could go up to 1200????

badssz

ok - My fuel pressure is 45 psi.

The maf is a aftermarker G-MAF, and the injectors are 30# accel's and the pcm has been re-programmed by Ion at madz28 - But I can't seem to get ahold of him......

The 02 readings were taken at idle....

and I thought it may be the map- so I unplugged the connector to it and drove it home (5 miles) with no change to driveability. Is that normal?

Tim240z

Seems like too much pressure at idle (off boost). My N/A Z28 only runs about 34 lbs at idle.

badssz

Yea - I think I read in another post that the accel injectors are only supposed to be set at like 39 or something like that....I will adjust it down, but will that really affect it that much? Doesn't the pcm control the injector pulse?

badssz

ttt?

Injuneer

Set your fuel pressure at whatever you told Ion you were going to run it at. He should have asked you that question, and then programmed the injector constant appropriately. And, set your fuel pressue to specs (whatever you told him you were running) with the vacuum line off.

Running 45psi vs the 39.15psi generally used for pintle style injectors will only increase the flow rate by about 7%, which should be within the capability of the PCM to adjust for... but I'm not sure you are measuring your fuel pressure correctly. What is the MAP reading at idle?

badssz

Well - after a lot of testing today I have come up with several things that might help.

everything I scanned appeared to be operating properly except the 02's the right bank was reading at 1093 constant the left bank would show anywhere from 130 to 900 - and woud just change almost immeadiatly. I am not sure how they are supposed to read, but this seems odd to me.

the map was reading between 34 and 37 depending on request for throttle - seems ok - all the other sensors seemed to be fine - I checked for a vacuum leac around the intake manifold and intake tubes - none.

When I first started it, it ran awesome - for the first 5 miles, never missed or overloaded at all. Then when the temp got to about 180 degrees, started loading up - almost like when the pcm went into "closed loop" - at idle - it would load up, then idle fine, and intermittently miss, whne it would get to the point of almost dying like 300 rpms, it would correct it's self and clean up instantly. This leads me to believe it's in the pcm and the fuel curves are most likely off - unless the o2's are soo far out of wack, it's reading lean and totally dumping fuel, killing one bank of the engine, until i manually override it. by opening it up and forcing more air into the engine - I dont know.....Help!

Thanks

Paul

Fastbird93

Try swapping your O2's from side to side and see what happens. The one that's reading from the 100's to the 900's and bounching back and forth sounds like it's fine, but the one that's dead at 1093 shouldn't be like that. An O2 that craps out most likely won't set a code unless is totally craps out.

If you swap them side to side, you can watch the O2 Mv and see if the problem switches sides. At least that way you'd narrow your larger problem down to a side or an O2.

badssz

Just a update - picked up a new o2 sensor today, I'll be putting it in shortly - hope it works. I think it's the best place to start though.

PS - thanks for all the help.

Later

Hetfield

I bet you a case of beer that o2 will fix your problem.

badssz

Well Hetfield, I drink Bud Light in bottles!

The Damn O2 sensor did nothing - still runs like ****..... Any suggestions?