I have been having a idle issue with my truck. When I first start the truck it idles up and then down like normal but then a moment later the rpms drop down sharpley and then back up almost like a lopeing idle and runs rough like a slight miss. The idle in drive has been somewhat rough as well. I was thinking it may be a idle air control or mayby just needing a tune up. I bought the truck about 3 weeks ago so not sure when it was tuned up last. Anyone else have this issue?

 

My truck also did this. It ended up being the tps. Mine threw a few codes that helped me narrow it down. If cleaning the IAC doesnt fix it get the codes pulled. I hope you get it resolved. I know how it feels to buy something and start having issues pop up.

 

I have an 87 f 150 and I was having rough idle problems and it would often stall if I let off the accel. pedal or put it in gear.
I changed the Idle Air Control and the situation improved, but it wasn't quite right still (would stall and run rough once in a while-not as often though)
Then I changed the Throttle Position Sensor (TPS) and so far (knock on wood) the problem is gone.
You might try that. They were easy parts to change out.

 

2/3 can of Seafoam through air intake, 1/3 can in the gas. Won't fix whats broke, but it will improve the performance while your getting around to fixing them. Removes carbon deposits in combustion chambers & cleans Injectors. Repeat just proir to oil changes.(Cat/o2.safe)

 

i had this problem in my 97 4.6. i agree... run the seafoam! made it almost seem worse for a short while, but drove it for bout fifteen minutes, and i have never had the problem come back. that was about a month ago.

 

I had the same problem with my 96 150 5.8L.... it ran rough after start up and i had to give it throttle to keep her running.... i had to laugh though because it ran like what i call " a chevy motor" but after some time the problem disappeared without fixing or replacing anything! now the only code i'm getting is 172, where my left bank is running lean.

 

How many miles on the O2's?