I have a problem maybe someone could help me. I have a 1999 lightning with alot of mods. The problem I'm having is when I crank up my truck it will idle at 1500 for a couple of seconds then down to 900-1000 which was normal before may problem started. Now my truck idle's up and down sometimes almost cutting off I cleaned my air filter and and my mass air sensor checked for vacum leaks found none my next thing to do is buy a new IAC sensor I guess. Anyone have any suggestions?

 

Indeed sound like the IAC! I've had to put a couple of them on my Mustang GT and that sounds like the symtoms I had.

 

Most likely the issue, you should try cleaning it first. Sometimes it works, other times,,,,

 

I tried that also the other day. Im going to buy a IAC sensor tomorrow.

 

I just changed changed my iac not to long ago. Tried cleaning it, but no luck.

 

Were you have the same problems as I listed.

 

My truck had the same idle problem. Replaced the TPS on the passenger side of the throttle body and the problem was solved. The voltage on the tps was .75 volts and would not increase when I moved the tps. Put the new one on, set the voltage at .99 volts and the shift was smooth and the idle was back to normal. Check your TPS voltage first.