Here we go. I have been lurking, reading, reading, and reading some more. I believe we have the problem solved but wanted some input for different angles.

2001 gmc sierra with stock computer

-L92 with katech cam/knock adapter and map sensor extension
-lingenfelter 58x to 24x reluctor wheel conversion box
-long tube headers
-K&N intake
-cam 222/224 566/568 112LSA
-nick williams 92mm throttle body

So truck has been sitting for over a year, I put gas in it and it fired up but idled rough at 1500 rpms. Had a quickie tune from previous owner.

New plugs, wires, battery, seafoam in the gas tank and it cranks and runs at around 1000 rpms.

During the tune the lingenfelter box would give a red light and the computer showed a lost signal for rpms after the motor warmed up for a bit. After a short break truck would do same thing. Called and getting new lingenfelter box because of some recall. So is there anything else that could cause the rpms to surge at idle? 800 to 1200 over and over like I was feathering the gas? The truck also would not crank unless the tps was at 60%, more or less and it would not crank. Thanks for your time.

Grant

 

I just installed an l92 in my dualsport car and am getting the tune dialed in now. You didn't specify, but I'm assuming you have an automatic. My car was doing exactly what you said with the idle surge and it was because the tune was for a "heavy" flywheel (automatic) and mine is a smaller "light" flywheel for a manual. Once i installed the "light" flywheel tune, it idles perfectly now. May not be your issue, but something to think about.