Advanced Tuning Question- High RPM throttle cut and limp mode
#1
Advanced Tuning Question- High RPM throttle cut and limp mode
I'm looking for some real knowledgeable help with an issue on my 418 LS3 swapped 99 FRC.
I have a newly installed 418 LS3 swapped into a 99 FRC vette track car that originally had an 350 LS1 with a 78mm throttle. The engine was professionally built by a very reputable builder and usually runs fine. However, at WOT at high rpm's the car will completely shut the pcm down and go into limp mode, sputtering and missing until the car is shut off. It then fires right back up as normal and runs great until you repeat the high rpm WOT. It seems to need to have WOT and about 5200rpm both to occur. NO FAULTS ARE SET
We have had 2 different throttles, 3 different pcms, and cals ranging from the current tune back to stock and nothing helps. I have one of South Texas's best tuners working on this, as well as the engine builder, and we are all stumped.
If anyone has any input or incite I would appreciate it.
Thanks,
Mike
I have a newly installed 418 LS3 swapped into a 99 FRC vette track car that originally had an 350 LS1 with a 78mm throttle. The engine was professionally built by a very reputable builder and usually runs fine. However, at WOT at high rpm's the car will completely shut the pcm down and go into limp mode, sputtering and missing until the car is shut off. It then fires right back up as normal and runs great until you repeat the high rpm WOT. It seems to need to have WOT and about 5200rpm both to occur. NO FAULTS ARE SET
We have had 2 different throttles, 3 different pcms, and cals ranging from the current tune back to stock and nothing helps. I have one of South Texas's best tuners working on this, as well as the engine builder, and we are all stumped.
If anyone has any input or incite I would appreciate it.
Thanks,
Mike
#5
I'm going to say either the LS3 tb or the MAF is hitting the fail point. At that shut off point see how many hertz it's reading. May need to be patched under the OS tab of hpt