Newbie to LS motors. Swap problem

**soberover** · 11-29-2022, 12:48 PM

Greetings. I'm an old shade tree from Texarkana, TX. It's good to be associated with you folks cause I'm an LS rookie, and I need all the help I can get. I swapped a 2000 LS1 4.8L into my 1995 Silverado, standard cab with short bed. It had a 4.3L v6. After mounting and setting the engine and trans(4L60e), I installed a stand alone harness from one of the cheapies. Everything hooked up ok and i bought a reflashed PCM with vats, rear o2, egr, and all emissions deleted. I kept the old computer to run accessories and stuff. I'm running true 2 1/2" duals with flowmaster 50 and out the back. I use front O2 sensors. I installed a BTR stage 1 cam with 208/209, .492/.492, 107 LSA. BTR said springs not necessary, but I installed BTR springs that are one step up from stin the truckock. All new rings,bearings,oil pump,all gaskets. So I have 2 pcm's in the truck, one for engine and other for all the rest. Also constant 55-60 lbs fuel pressure.
Problem is this: Sometimes engine will rev to 4500 rpm on start-up and take 30 sec or so to come down. Sometimes engine will accelerate on it's own and if I go to neutral, the rpm's are about 4,000. The engine does not idle well and will surge and die when letting off the throttle. No vacuum leaks with smoke test. New TPS, IAC, MAF ,MAP. It's drive by cable and it's free. No codes and I'm stumped. Does anyone have any ideas? BTR said I don't need a retune on the PCM with the cam. Thanks

**bluehawk2000** · 12-03-2022, 05:26 PM

You need a tune

**soberover** · 12-05-2022, 06:25 AM

Thanks, I appreciate it. New MAF solved all my problems, though I will get a tune for the BTR cam idle. I had a new aftermarket MAF, but I replaced it with an AC Delco OEM, MAF. Lesson learned on the aftermarket sensors. Never again, they're junk. Thanks again

**bluehawk2000** · 12-05-2022, 07:50 AM

Originally Posted by soberover

Thanks, I appreciate it. New MAF solved all my problems, though I will get a tune for the BTR cam idle. I had a new aftermarket MAF, but I replaced it with an AC Delco OEM, MAF. Lesson learned on the aftermarket sensors. Never again, they're junk. Thanks again

No reason to have an after market MAF with what you're running, and if you do put one on it, you most definitely need a tune. Here is a link that explains it a little more.

http://www.ls1.com/forums/f9/attende...aining-145347/