5.8L idle woes

[daddygeee]

I own an '88 F250, 5.8L; my good friend owns an '89 F150, 5.8L with the same symptoms so I'm looking for a two-for-one solution. Both idle very high cold and run poorly until mid throttle. No hesitation on acceleration nor stumble. TSP? or Idle Solenoid? Both guzzle fuel. Ideas from my new found Fanatical Ford Friends?

 

[mrfixit]

sounds like EGR problems to me. But before you go buy a new EGR valve, check the condition of the Vacuum line going TO the EGR. There is a TSB out on that, even a Recall, because the heat from the exhaust manifold would fuse the line shut. The fix is a heat shield and to replace the defective line, rerouting it with zip ties away from the hot spots.

If either of you wind up needing a new egr, lemme know. I got one brand new in the box for about 45 bucks, lol... I bought it back when I had the aforementioned troubles with MY 88....

 

[Skandocious]

Yeah my first thought was the IAC (idle air control), but the EGR is a possibility too. Both of those parts can sometimes be cleaned instead of replaced, depending on your problem. So don't go throwing parts at it quite yet.

 

[daddygeee]

As we speak I'm cleaning the throttle body, IAC, and egr port. The TSB I read said not to clean the IAC with carb cleaner but to use the special super duper cleaner Ford provides (is this intake manifold spray cleaner?). Is this relevant or just clever, aggressive marketing to saps like me who are afraid of their own shadow? I'll put some vac on that line to ck integrity; vac prob. makes sense. Thx.

 

[mrfixit]

I know it's a pain to spend the extra bucks, but my position has always been that if I must err, I'd rather err on the side of caution. That being said, since I don't have a MSDS sheet on the ford product in hand, I'm going to say it's entirely possible their product may be certified to not damage o-rings, or other sensitive components. However, since this is WELL beyond warranty, it's not like using another product would void such warranty... In other words, the choice is YOURS, lol.
Also pull the sensor off the top of the EGR and make sure the diaphragm still has its integrity.

 

[Skandocious]

I have heard of guys using a generic solvent like a carb cleaner or brake cleaner with no adverse effects on the valve.

 

[bowtiehatr]

check for a vacuum leak where the upper and lower mainfolds meet. seen many gaskets go out. also the tp sensor could cause a number of issues as well, bad thing is you have to use a meter to diagnose due to lack of pids. the only way the egr will cause a issue if it is stuck open or if the gasket is leaking where it meets the intake. also you could have a bad 02 sensor, map sensor, iac, the list goes on. see if you can get some codes pulled and holler back.

 

[mrfixit]

Map sensor for sure would cause poor mileage and bad idle, but it would pretty much be through the whole range, wouldn't it? These 5.8's are known for that cheesy vac manifold too, with all the vac lines attaching in one place, and the MAP sensor line seems to be prone to it more than the others. Trace that vac line back to it's connection and make sure it hasn't slipped off!