Gentlemen,

Ordered a Madtuner mail order tune and recently installed in my 95 Formy Lt1. Car has Intake, exhaust, longtubes, no cat, performabuilt stage 2 4l60e with 9.5" 3000 RPM Stall 3.42 gears no internal engine mods.. Ordered the tune as a replacement computer for my car (so tune already loaded on another computer) and swapped my stock for it. Car ran great at idle before installing new computer but after install @ idle it stumbles, surges, almost like idle is too low where engine feels really rough/off balance and emits knocking type noise.. Under load/throttle above Idle it runs perfect with a noticeable gain in power... Dont know what the deal is. I never really drive the car so I dont know if it needs to "re-learn" or if there is something wrong with the tune but its def not normal.. THIS THREAD IS NOT A KNOCK ON MADTUNER! I'm sure it's something simple, i've tried to email him with no response unfortunately so i'm coming here looking for any answers/suggestions. Thanks in advance!

 

All the mods were done before the pcm swap and the car ran fine?
No mechanical work was done immediately before installing the new pcm?
Have you tried swapping the old pcm back in?
Have you contacted him to have him take a look at the tune he sent you? It is possible a table got goofed up or something.

 

So if you swap back in the stock PCM, does the stumble go away? [Edit]Dwayne beat me to the punch.

 

The first thing you should do is contact Ion. I'm sure he would love some data logs from you, as well.

 

I never swapped the old PCM back in.. I really never drive the car. In fact I installed the PCM, started the car up for a a few seconds and left. Then the next time I was at my shop (after returning stock PCM) I started the car and let it come to temp and thats when she started stumbling at idle.. Driving around its perfect! I've done zero mods in over a year and the car ran perfect with factory PCM..

 

I am going to give him a ring soon and see what he says. Need to get a cable/software to log data and send to him..