2000 AWD Hot Stalls - Idle good

[canthony15]

This is my first post and I hope it doesn't get too long winded. Last summer we took my 2000 AWD (5.0) to the mountains towing a medium sized pop up tent trailer. We were in the tunnel crossing the continetal divide when I pressed the gas and felt the car slow down. I thought the engine had died but I let up on the gas and the tach looked OK. Press the gas and it jerked a little and had no power. Fortunately we got through the tunnel onto a long steep downgrade of about 2 miles. The problem remain, press the gas and the engine slowed down. I pulled over and looked around under the hood (like I would find anything). after a few minutes, I restarted it. Started right up and idled fine. It ran OK for a while and then the problem repeated. I pull over. The idle is fine but I press the gas and the RPM drops instead of rises. Turn off, wait a few minutes. Restarts fine and we go another 20 miles. We finally made it to our camp site. Two days later we drove back to town with no problems. There was a code about low fuel pressure so I replaced the fuel filter and drove it until yesterday (nearly a year). Yesterday it hit 103 here. driving in town for about 45 minutes with MAX AC, I got the same stall pattern again. I got it home and parked for 30 minutes. Drove it around for 30 minutes with AC off and the problem repeated. This year there are no codes. When I pull over, the engine idles fine but pressing the gas causes the RPM to drop to very low value. I tried just holding the pedal down and the engine almost dies and then revs up a ways and then drops back down and revs up a little higher and back down (peddle still on the floor) revs up even higher. Up and down like this about a dozen times, each time the max RPM it reaches is higher until the RPM peaks high enough that I am uncomfortable with it and I let up on the gas. Takes maybe 15-20 seconds to cycle through all that. The idle always seems fine. Always starts immediately. I drove it to work today (19 miles) with no problems. I have to see if I get home tonight since its supposed to hit 100 again.

I've read about similar problems and about the IAC. But none of the posts I've read have the "good idle" symptom, and none of the posts I've read say what it was that eventually fixed the problem. Last summer, I was sure it was the fuel pump with the low fuel pressure code, but I replaced the fuel filter and never saw the problem again (but I haven't towed since then). This year I didn't get any codes. The symptom only seems to happen when conditions are extreme, at least so far. I have no clue how to approach this. I am thinking about buying a new IAC but I don't want to wait until I'm towing 100 miles from home to find out it didn't work. The vehicle has 87000 on it and the only problems so far were a bad spark plug wire and a broken spring in the transmission. Ideas anyone?

 

[exploded99]

If it idles ok, then the IAC is fine. The IAC has nothing to do with engine operation above idle - as soon as you touch the accelerator pedal, the throttle position sensor takes over.

I think, since you had a fuel pressure trouble code, the place to start is with a fuel pressure test, preferably on a really hot day with the engine fully warmed up. Sounds like your fuel pump is getting flaky.

The 5.0 does not have a separate fuel pressure regulator - the pump develops 65 psi (that's a lot). Acceptable tolerance is +- 8 psi if I remember correctly.

 

[ronin2501]

I have experienced this same issue but ONLY in high temperatures. What I have found is that the Ignition Coil is getting to hot. The resistance values would raise and the ignition output would be dimished. This would cause a miss at cruising speeds (towing, or not) and if I turned the engine off, it caused a no start condition. I don't know if this holds true for Ford, but on some vehicles "Namely Mitsubishi" when the ignition control module or coil fails or has an open the PCM or "ECM" will cut off the fuel. (In my case both of my O2 sensors reported a lean condition with scanner hooked up while this problem was occuring at a cruise speed, and also reported a code 214 CID Cylinder Identification Circuit Failure)

If I let my Explorer sit for a few hours I could go right back out and it would start back up. I have a non-contact thermometer and the temperature variance would be close to 125 degrees on the Ignition Coils before it would begin raising resistance values. Soon afterwards the problem would start again.

Replacing the Ignition Coil resolved this issue for me permanently.

(I would also check to see that the voltage supply to your ICM and Ignition Coil matches the same voltage reading as your current battery output)

 

[asessnios]

can't say for sure, but to me that sounds like a fuel delivery problem .

unless your engine is missing randomly until it gets warm..i wouldnt suspect ignition coil.