Ok, so I have a 1989 f-250 with the 351w, It's got 97,000 miles on it and i've got an idle issue, it either idles really erratic surging from 500-1000, it just goes up and down, or else it idles up at almost 3000 rpms, I've already replaced the IAC , the PCV valve, the Throttle position sensor, I've also replaced quite a few vacuum lines, My questions is, what else could be the problem? none of these have fixed or even helped the problem. I've checked for codes and the only codes I'm getting are from the egr being deleted. Id appreciate any input thanks.

 

put the EGR back in it.

people always move away from factory setup then wonder why **** doesnt run right...

Sorry rant over.

 

And that will do nothing to fix the issue.


To the OP:

The most common cause of a rolling idle is a vacuum leak. I suggest to replace all if the vacuum lines to eliminate future problems. I also advocate testing each vacuum circuit with a hand held vacuum pump/gauge.

A worn throttle body can be a source of a vacuum leak.

TPS is the second most likely cause of a rolling idle. Verify your new TPS is working properly.