Hope someone can help here!!! I just had a 383 stroker engine built with a complete Lingenfelter super ram Intake. The engine was built by North Jersey Performance for my 91 L98 vette. I also have the following mods: vortex ram air Induction, adjustable fuel pressure regulator set at 45psi, high volume fuel pump, 26# Injectors, no frisbee, coolant bypass for the 58mm throttle body, smog pump eliminator pulley, Lingenfelter 1 5/8 long tube headders, high flow cat, Borla exhaust, 3:54 gears, Tci street fighter trans, high stall torque converter. Lingenfelter recommended that I buy my custom computer chip from Fasterproms In florida, because that Is who they also use.
Now here Is my problem, I've just put In chip #11 and the car still runs like crap. To be more specific, while driving under mild acceleration (city driving)
when the engine Is warm, the engine starts to hesitate at 2000 rpm then back fires at 2600 rpm and continues to do both until I reach 2900 rpm and then the car takes off like a 450 hp engine should. As I said, It only does this during mild acceleration. On wide open throttle, this problem doesn't happen through that rpm range. I've had the car hooked to a computer for a block learn analysis and the numbers are right on the money????? When the car backfires the retard nocks the timing back 1 degree. Fasterproms has added fuel, taken fuel away, Increased timing, decreased timing over the course of the 11 computer chips they sent me. They also talked to North Jersey performance who built the engine to see what he put In the engine (heads, cam etc...) Lingenfelter had me remove the 40,000 volt super coil and replace It with a stock cap, rotor and coil...didn't help Then they said I had too hot of a plug(bosch plus4) and dropped down to a plug with the next lower heat range and they changed the gap from .36 to .35 Then they said my distributor might be off one tooth, but they pulled that out and It was dead on.
No matter what chip they sent me the same hesitation and back firing occurs at the same rpm range. There has also been some Isues with the car stalling at cold start up with some of the chips. Every time I Installed a new chip, the chip would run fine (no hesitation or back firing) until I had about 15 miles on the chip and the problem comes back.
I'm about ready to drive the car off a cliff, I'm so frustrated at this point and don't know what to do next. Can anyone help with a solution or suggest a corvette tuner who burns chips???????? and has a dyno???? and Is In the North Jersey area
It's been 2 months since I had the engine built and I've missed 2 race days for the corvette challenge at Englishtown NJ
:banghead: :mad :eek: :cuss

 

Sounds liike you have some really competent tuners working with you on this.

Your problem seems to be part throttle performance since you said the engine runs fine at WOT. Do you still have the stock PROM that you can try just to see if it cures the part throttle problem? It'll probably be too lean for WOT runs though.

Is the engine going into closed loop?

Can post the data you logged?

Have you tried swapping in a different ECM to see if it could be the problem?

Do you know anyone in your area who is running the same ECM that you could borrow just to see if it makes a difference?

Just my thoughts.

Jake

 

ONLY ONE THING TO DO NOW TALK TO SKI_DWN_IT HE IS THE MAN ON FORUM FOR CHIP BURNING AND DIAGNOSTICS..

 

I don't have the stock prom, my last prom was from breathless performance and never had a problem with It.
I believe the engine Is in closed loop for only a few miles until It warms up and the problen appears (as per corinthian motors In ramsey nj
I don't know anyone nearby to swap the ecm, but I asked corinthian motors(who normally works on my vette the last 3 years) and they think It's still the chip and not the ecm

 

What does your dyno graph look like through the indicated rpms? I had a very similar problem on my 396. That and an extremely lean condition at 5400rpm that could not be cleared up frustrated me to no end. I got tired of playing with it and went with the Accel DFI Gen 7. No more problem.

 

He is busy as a bee(like anyone else good) but contact ski_dwn_it to do a chip for you.

He's in Pennsylvania and is VERY good. I sometimes wish my stock computer we're still intact so He could improve it...but that's another story.

I know where you're coming from. Hang in there. :cheers:

 

I don't remember, is a 91 MAF or Speed Density ?

In any regards, I have the "Exact" same problem with my 85, 383, Superram set-up since I put on the AFR cylinder heads. Although it doesn't backfire at 1/2 throttle at that rpm, but just hesitates fairly severely. At WOT it is fine. btw, I am running a FasterProms prom too.... (Formato chip), that has been tweaked a bit here and there by forum member Bowtye8. But I don't think its the chip in my case.

I haven't really been worried about it though... I can usually fix these things through experimentation, which I haven't really tried yet due to time restraints.

In any regards, I'll be interested in your fix. Please post any progress, and hang in there, these things have a way of working themselves out.

cheers,
Beach Bum

 

Thanks for the info

 

I have 90-91 MAP PROM information that will help, if you need it. I have gone through similar problems.

This may not be a problem, but pull a spark plug and check very closely for signs of running too hot a plug. I discovered this after about 50 chip changes.

Good luck.

 

50 chip changes :eek:
and i thought 3 different on three different motors were alot :D :cheers:

 

Well I may be slow - but my car is fast. :crazy:

 

Please send the Info, any help Is much appreciated. Thanks

 

Not to make light of your problem, which unfortunatly I am unable to help with, but if it runs fine at WOT, why have you missed the races???

RACE ON!!!

 

Yeah know...I think you are right!!! WOT no problem and that's all I use at the track. TIME TO RACE!!! But I still need to fix the problem. Any other help out there??? :steering: :party:

 

"contact ski_dwn_it to do a chip for you" Unless something has changed, he won't touch a speed density system.

 

Speed Density car are very tricky to tune. One may tuned it but chance is you won't be able to tuned for good hp or run right. Only one person can tune SD cars is Shalin that I know of who can tune SD car to run right. The down side is he won't do mail order tunes. Street tune/dyno tune only. I remenbered he told me before and say that Ed Wright SD tune are so so and he has retune Ed Wright chip and he was not impressed(specific SD cars) made a lot changes to make the car running good.


Bruce

 

My 383 stroker had the same problems a few years ago. After hooking up a wideband O2 and EGT it didn't take me long to see that:

#1. 26 lbs fuel injectors/stock fuel pump wasn't enough
#2. My fastchip programming/fuel curve/timing was way off
#3. If I didn't fix it right away I would be installing another engine very soon!

Find someone to tune your car out soon. Reading the ECM through a data logger program is only a small piece of tuning. Hook up some gages/data logger and slowly...slowing walk the car through the RPM's and STOP if your EGT and AFR go out of range.

I promise you'll learn a lot about what makes an TPI/EFI car tick before it's all said and done. I did!

Frank :steering:

 

Thanks, any additional Info would be appreciated, such as what you did to fix the 26# Injector & stock fuel pump. I already have an Accel high volume fuel pump (in tank)

 

I don't think you have a "capacity issue" with your pump or injectors although if any of them crapped out that could be it. I would get on a dyno with a wideband and a scanner hooked up and do a few dyno pulls. Then either send the data back to Formato or to someone like Jesse.

I spent over $1000 to have a custom prom burned while on a dyno near raceway park and I don't think I got good value for the money. In fact I have been thinking about giving Jesse (ski dwn it) a shot on my set up which is simialr to yours.

BTW, I first wasted $350 on an Ed Wright prom that ran like crap. I believe you can really tubne these things unless you have wideband AFR and data scans from your ecm. Just my opinion though.

 

I tried ski_dwn_it and he hasn't gotten back to me.
HELP!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Does anyone know of someone In the New Jersey area that can help me??? I just received my 12th chip last night and the same problem (hesitation & backfiring between 2000 & 3000 rpm) Is still there. This Is sooo frustrating after 2 1/2 months and over $1500 spent just trying to tune the car. I'm even thinking of selling the car, but who would buy a car with a new engine that doesn't run right. UGH!!!!!! :banghead: :banghead: :banghead: