I've a 95 4x4 with the 5.0 liter and having trouble with the idle on start-up. Someone told me it sounds like the MAP sensor. So, I got hold of the Haynes manual for 80 thru 96 2 and 4 wheel drives and it does say my map sensor should be mounted on the firewall next to the a/c condensor. It's not. I can't find one anywhere but if it's not where it's supposed to be, then where is it? Does this model truck and motor even have one? The book shows one but doesn't differentiate if it's on a 6 cyl or an 8. Help would be appreciated. Thanks

 

Is your truck by chance mass air flow.. i.e is there a sensor on the intake tube?

 

I see you posted in another thread that you in fact have a MAF - so clean it and also clean the IAC.

 

The Haynes manual wasn't updated after '92, so it doesn't show anything about MAF or CCD. MAP is the characteristic sensor for speed-density EFI, so MAF engines don't have a MAP.

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I wouldn't mess with the MAF - they're delicate, and don't often fail on these trucks until you mess with them. But if you feel the need, only use hi-quality MAF cleaner; not carb cleaner, brake cleaner, ethanol, gasoline, or anything else. CRC & BG make good MAF cleaners.

I'd look for other causes, like: dirty battery terminals, vacuum leaks, EGR leaks, sticky IAC, fouled or burned plugs, misrouted plug wires, PIP fault, low fuel pressure, leaky FPR, incorrect timing (stretched timing chain), uneven compression (sticky rings or lifters)...

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If you are using an oiled air filter such as a K&N, it's very possible your MAF is oil fouled and it needs to be cleaned.

 

I'd go straight to the sticky IAC as the most likely suspect.

They really start showing up a lot this time of year.

 

Yes, I do have a sensor in the air intake tube. That would be the MAF. Thanks for the insight and I will check the IAC.

 

Okay, I've replaced the IAC unit and dismantled and cleaned the entire throttle body. I've also cleaned the MAF with CRC maf cleaner. The TPS was replaced a few months ago. All to no avail, the truck started fine and revved to about 900 rpm then revved up to about 1200 and ran like that for a few seconds then fell off abrutly and almost died but caught itself and then ran about 900 rpm, still too fast, right? Then after it warmed up, it ran fine and the idle was right where it is supposed to be. Any thoughts?

 

900 rpm is fine, as long as you weren't in gear.

 

Well, 900 rpm may be fine when it's warmed up but my problem with fast idle is still there. My son thinks it might be a fuel pump but if that's the case, wouldn't the truck do it all the time and not just when it's cold? Simply put, the truck runs too fast when started cold but runs fine after it's warmed up.

 

How high are the RPMs when it's cold? The ECC will have the truck run at a higher RPM to warm it up when it's cold.

 

Okay, let's back up a tad. The truck just started doing this about 4 months ago. Up til then it was being driven every day. This "problem" started about 2 months after I retired when the truck has set for days without being started. But not more than three or four days at a time. The RPM's would be about 1200 to 1300 and then go up after about 15 seconds to around 1500 to 1800 then after about 20 seconds it will fall down fast and die or stumble and almost die sometimes. After it starts the second time the idle is better but still too fast for being fuel injected, I know this because I've owned a lot of ford trucks with and without FE. Then after the truck is driven a short distance the idle is good and if the truck is shut off and restarted the problem is gone until the next morning when it is restarted. Check my above posts to reiterate just what I've done. The one thing I'm thinking now is that it may be a vacuum leak somewhere but where? Thanks for all your patience.

 

Did you check everything else I suggested? Did you check for codes (not all turn on the CEL)? V8s are known to suck the plenum gasket (9H486) in near the T-40 bolt in the middle. Use a mechanic's stethoscope (or 3' of garden hose) to listen around the idling engine for an obvious hiss. The TB will hiss from inside, even though it's not leaking.

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Thanks Steve, I'll work through those suggestions although it has new plugs and wires and new air filter and new IAC. I took the truck out this morning after it sat with the neg battery post unhooked for a day and it started and idled really fast then fell off almost immediately, I restarted and then it was a little better so I waited till the idle calmed down (about 3 minutes) then drove the truck about 8 miles and shut it off. When it started again the truck idled about 1200 then fell of to about 900 so I put it in gear and headed home. When I got home it ran fine, nice low idle so I shut it off, waited and then started it again and it idled great. Do you suppose the comp. needed to reset? Also, I'm experimenting with running only on the front tank then switching to see if there may be a difference there too. The truck has a history of running rougher on the front tank when running around town, but if the tank is switched to the rear the roughness disappears. So, maybe your suggestion of fuel pressure may be a good lead. But, I'll continue to pursue all options. Thanks again.

 

There is no "reset" - what you did was to clear the adaptions. It will re-learn those same adaptions after a while, and the symptoms will return. Clearing the adaptions is only to delete bad adaptions from bad hardware that has been changed. Your IAC obviously wasn't bad (or replacing it would have changed something), so there was no need to clear adaptions.