vetteboy86

First of all, by high RPM I really mean in the ball park of 5k. I don't know exactly.

I've come a long way in trying to pin this annoyance down. Things I have replaced and added along the way include: AFPR, fuel injectors, fuel pump, fuel filter, MSD6AL, coil, module, cap, rotor, plugs and wires are fairly new.

I originally thought it was a fuel delivery issue, and went through the fuel system, but it turned out not to be. I then looked at ignition components, and that didn't have an effect. So with the help of this forum, I did some tuning of my own, on top of tuning I had custom done. I also installed an LM-1 in the car. When I first started using the wide band, my wot afr was down in the high low 11's high 10's. I have since then been able to control it in the middle 12's with no change, up to mid 13's with no change.

So I am curious as to what else can cause this problem for me. I am now wondering if it is a timing issue. I don't see any spark knock in the high rpm's with datamaster. However the person that burned the chip must have done something, because as soon as I jump on the gas, the computer pulls 6 degress of timing, but slowly gives it back while the rpm's increase to redline. I could post a picture of the log. I had a buddy look at it a while back and he though it was goofy, but I would imagine it has a purpose.

Well any suggestions would be great.

IroczInOz

Could it be an injector reaching max duty cycle?

I am just guessing here, what kind of injectors you running and what kind of power you have?

vetteboy86

I'm not sure what kind of power I am making, but the motor is a moderately worked 383. I put 30# injectors in. The duty cycles on them look good however while scanning in Datamaster. I can go to a log and get an exact number for you though. So what I don't understand is why my afr looks decent. I would think that if I was running rich or going lean, my afr would reflect that.

I have also thought of the possibility of a bad plug wire or something on the opposite side the motor then my wideband is in. However I have gone through a set of wires during this issue.

vetteboy86

Plus, I think i may be rich because I do notice some popping out the exhaust when this occurs which indicates un-burnt fuel during the exhaust cycle. Could this be a timing issue, not enough?? or to much??

vetteboy86

This sounds similar to my problem, but I don't believe I am going lean because my afr looks fairly steady. info.https://www.thirdgen.org/forums/tbi/...st+out+popping

But it does feel as if I am hitting some kind of rev limiter. I actually took the chip out of the 6AL because I thought it was defective.

vetteboy86

Well if what datamaster is telling me is correct, my fuel injectors are not going static. At 5200 rpm's, injector pulse width is 7.07 and injector duty cycle is 61.5.

IroczInOz

Do you do your own chips? What kind of rev limiter is on the chip, check that. You might also want to duck into the DYI PROM forum and ask in there.

vetteboy86

Thanks for the reply. When the motor was rebuilt, I thought I could manage on the factory settings, but was wrong. I had a company burn me two tunes. I have since then been modifying that. To my knowledge the rev limiter in the software is 10k rpms. I questioned my MSD 6AL for a while and pulled the rev limiting module out of it.

rgarcia63

I believe we're n the same boat.

Don't think it's a timing issue.
I was getting a MAF and EGR code, I swapped with a friend, no MAF code, but still had EGR code and ran the same. Replaced the MAF, one code to go.

What Cam? Is it self EGRing? Disable EGR and do a test run.
I came to the conclusion that my comp cam 262 was self EGRing so I disabled the ECM EGR and that took care of the code and the wall I was hitting at part throttle, but still had a noticeable missfire, and afterfire.

I have a crane HI6s box/LS92 coil and their 8.5mm firewires, but found that their box requires 300-800 ohms/ft, but their wires are only 25 ohm/ft. I replaced the wires with a custom set from Kingsborne Wire Werks (500-800 ohms) that greatly reduces the missfire barely noticeable now, and a random afterfire, still there, randomness increases as it warms up.

Headers?
SLP 1/34" with A.I.R. is what I have.
A leak can cause those symptoms, because it's random now I'm suspect that heat expansion, and or vibration is causing the leak to come and go.

I do hear a ticking noise, but thought it was my injectors, now I not so sure.
Will post when I find out whether it's a leak, or not.

We may have the same symptoms, but may need totally different solutions.

vetteboy86

I have disabled the EGR, and currently have no codes stored. I do have a set of longtube headers on the car. I haven't noticed any signs of leaks though. I thought about adding or taking away some timing to see how the issue changed. I don't to go crazy, as I know what that can do, but with ignition and fuel out of the way, unless there is something mechanically wrong i'm at a sever loss.