Running a 5.3 LM7 modded into an 86 k10. For whatever reason, on startup, the engine comes to life as normal, revs up to about 1200 rpm or so for a moment, and then begins to settle down towards idle rpm. However, (most noticable when cold), just as its starts to drop back toward idle rpm, it jumps again to about 1500, as if started again, and will then settle back down to normal idle.

When warm, it does do this at all, or not that I can tell. Mid-way to operating temp, it still does, but less noticable. Mostly happens on the first start of the day. Not an issue, just curious why it does this? Don't have any DTCs, but I do have an intermittent p101 that comes and goes. Ideas?

 

MAF flow code will cause a fluctuation like that. Make sure you computer calibration is for the MAF you are using. Are you using the 5 wire or 3 wire with separate AIT sensor?

 

Thanks. I was/still am having intermittent p101 codes, which would go with you're theory. The computer is setup for the stock 5 wire maf which came stock on the engine. I haven't changed the intake setup whatsoever; stock intake flexy-rubber hose with tight clamps. Only aftermarket peice is a cone K&N attached to the end of the hose.

 

Mine does this too so I'm curious as well.