I have a 1993 F250, 5.8 liter. When the truck starts, it stays at about 2500rpm idle. A local mechanic looked at a bunch of things but nothing helped. Any ideas?

 

Have you checked for vacuum leaks? Don't laugh, it will do it....





That's some IDLE!! I go down the road at approx 2000 RPM running 70...

 

I think they did check for vacum leaks. It is my father-in-laws truck. He said at idle it will do 50mph going down the road.

 

The most causes of a high idle like that is a vacuum leak as mentioned before, a faulty TPS or IAC. It is always a prudent idea to check for codes before replacing any parts. How did this "mechanic" check for vacuum leaks? If the IAC is unplugged does it still happen?

 

I do not know if this will help you, but my truck idle's at around 2000 rpms. When I got it the seller said that was normal, bull----. I replaced ever sensor, upper intake gasket, vaccuum hoses, check codes and it stills does it. I have been all over the internet and find people with the same problem but no answers. What I discovered about a month after I got it, if I hit the gas (rev the motor for a brief second) right when the motor starts running, the idle goes down to normal about 98% of the time. If it still idle's high I just repeat the above step. I been doing this for 2 1/2 years and 20,000 miles. I think mine is the computer, but I am to cheap to replace it. I figure I just keep driven it until it breaks down. It cound also be one of the new sensors I replaced was bad when I got them.(autozone brand)

 

I have the same problem, not sure exactly what the idle is since its a 94 but its way too high. I have unplugged the iacv so its not so rough on it. Also having trouble with it shifting late and hard, im wondering if it is my pcm since it also wont return any codes. If anyone has any ideas on this it would be very appreciated, thanks.

 

Very classic symptoms of a faulty TPS. My truck exhibited some of the symptoms mentioned earlier when I first purchased it. After tracking down and repairing many vacuum leaks it would still intermittently jump idle RPM and like a previous reply "blipping" the throttle usually corrected the issue until the next start/run cycle. Finally traced it down to a corroded TPS connector. In the process of metering the TPS, which tested good by the way, I found the green corrosion. Cleaned both ends, applied some dielectric grease, works like a champ.

 

Many people have the same issue with the brand you mentioned.

 

Very well could be the computer if you can not do the Self-Test.

 

I just unplugged the tps and plugged the iacv back in and that put the idle back to normal and drove to the end of the road and it shifted at the normal times so I will pick one of those up tomorrow and see if it fixes it