I saw that many people have had problems with this in the past, but I did not see that anyone got to the bottom of this.

I would love to hear what kinds of things people have done to fix this problem...that is IF anyone has found a fix for the infamous surging idle.

 

I guess nobody has figured this one out yet. lol

 

After trying everything else, this worked for me.
http://mustang.c-f-m.com/index.asp?P...ROD&ProdID=649

Frank

 

I had the same problem surging idle and stalling. All I did was take the IAC off and cleaned it with carb cleaner and the problem went away, it runs fine now.

 

https://www.ford-trucks.com/forums/s...d.php?t=289737

https://www.ford-trucks.com/forums/s...d.php?t=494352

https://www.ford-trucks.com/forums/s...d.php?t=335894

all i can say is good luck.

 

Well, I have every manual that Ford ever published for my rig, I have every diagnostic tool that I can think of that would actually help in my situation (vacuum pump, vacuum guage, fuel pressure guage, OTC BREAKOUT BOX, volt meter etc. etc. etc.) AND I have a complete set of KNOWN GOOD sensors, egr valve, fuel pressure reg for the rig.

That being said, I think/hope that it's just a matter of going through some long hours of maticulous diagnostics.

I will report back with my findings.

 

grena,

I've been chasing some driveability issues on my '92 5.0L M5OD for a long time, and have given much hard-earned cash to dealerships. My general conclusion is that the dealer's techs pretty much have severe cases of recto-cranial inversion, and don't seem to know the difference between a muffler and a lug-nut.

So, yes, you're probably in for some extensive trouble-shooting. The idle surge on mine was caused BY THE DEALER, which I made them correct. However, I still had a random miss after a complete ignition tune-up. Turns out, this was caused by some expensive but not so high quality plug wires. Less than 10K on them, and they give a wonderful light show in the dark. Put the Motorcraft wires on, and it smoothed up considerably, but still a little sputter once in a while. New fuel filter, better again, but still not quite there. I've managed to whittle it down to ping/stutter under heavy throttle with a few sensor replacements.

Last night, while oggling it for the work needed for injector cleaning, I noticed some oily looking accumulations on the intake at the joint of the upper plenum and main intake. Uh-oh. Then, I read somewhere in here, that upper plenum intake gasket failures are fairly common on the 5.0/5.8 engines. This would have been nice to know just before I gave the dealer a blank check for a tune-up last year.

Look under the plenum, on the 1234 side of the engine. If it's leaking, dust will accumulate on the joint. The middle bolt on the plenum on that side is different from the other five, so I don't know if this is a design culprit or what.

So, today, I start disassembling and cleaning. Gonna be a long job, but looks like it's gotta happen.

 

alot of times cleaning your ICV with carb cleaner can do more harm then good. Ya it works sometimes but the carb cleaner can get into some of the elect. parts and usualy make them worse. The best thing to do it get a new one from your local autoparts store. I got one for $69 with a lifetime warrenty. its not the most expensive one they had but with it soo easy to install and lifetime warrenty i said what the heck. good luck with your truck!

 

I'm reasonably certain my ICV is working. If I disconnect it, it KILLS the truck. I'm not saying it and the TPS are properly adjusted, but definitely working. I can see where this would give me issues idling, but WOT going up a hill? Not likely. ICV don't count much when the butterflies are opened. This is one adjustment that Open_Wire has discussed in many threads about poor idle quality. I'm not having issues with the idle any more, at least nothing I'd call serious. There's an occasional shudder during idle, but VERY random and not very frequent. I kinda relate this to the crapoline we're all paying nearly $3.00/gal for, and possible starvation by means of constipated injectors.

Since my previous post, I've swapped the Motorcraft plugs installed last year (abt 15-20K on 'em) for a new set of Bosch Platinum II's. Again, significant improvement on low end/idle, but still being an asthmatic at WOT. All the Motorcraft plugs I pulled out looked like they just came outta the box, with the exception of the rust on the outside. To me, this just seems a little too clean with a year of use on 'em. All dry, all clean, all still at .056 gap (by label on truck)

Ran another test to check for leaking injectors (albeit the removed plugs told me so). Pushed the accelerator to the floor, and hit the starter. No start, not even a remote suggestion it was gonna hit on one cylinder after sawing on the starter for nearly 30 seconds. So, the injectors ain't leaking. Maybe plugged up with the fine quality fuels the oil companies are screwing us for. HATE it when I get lumpy gas. I replaced the filter earlier this week too. When I poured the residual fuel out of the inlet line, there was a lot of crud in it, that felt very gritty. Nothing looked like rust, but more like the tank's had very fine sand poured in it. Doesn't seem to have affected the pump, though. 42 PSI static test, 32 PSI idling, spiking to 40 when popping the throttle. same results with brand new FPR. This is well within specs. But, if the aforementioned crap made it past the big filter, apparently the nylon screens in the injectors have filled up with it.

The truck has NEVER smoked except on one occasion when I had a FPR fail on me at about 60K. Then, it ate nearly 12 gallons of fuel in 75 miles. It looked like a coal burning locomotive coming down the highway then. The tail pipe has ALWAYS been clean, and free of any soot deposits. The first one actually rusted from the inside out because of the water vapors from normal running.

Thanks for the well wishes for good luck. Looks like I may have to kill a few chickens to fix this one. Not looking forward to pulling the plenum to get to the injectors, but everything's pointing me in that direction. I'm beginning to think I may need to replace everything between the Michelin XC LT4's.

 

Well, my surging idle problem is not caused by any of my SENSORS. One by one I substituted with known good, and nothing ever changed. It's not a vacuum leak either. I couldent get the motor to pick up any PROPANE no matter how much I released and where I released it. Furthermore, I substituted the EGR valve, IAC and Fuel Pressure reg one by one with known good. Again, nothing ever changed.

That leaves the wire harness, computor and ????????????????

What else could cause the surging idle?

It has to be something electrical or vacuum controlled right?

Next, I plan on hooking up the BREAKOUT BOX and looking shorts and opening in the harness.

 

So far, nothing is jumping out at me as being abnormal as I continue to troubleshoot with the BREAKOUT BOX.