2000 Ford Expedition Go's crazy sometimes w/ lingering prob

Tiny
AJCALDWELL22
  • MEMBER
  • 2000 FORD EXPEDITION
  • V8
  • 4WD
  • AUTOMATIC
  • 130,000 MILES
This car appears to run fine most of the time. Every so often the gauges will go crazy and it will start missing and quit. Wait a little bit and it will start and run fine. The trans mission doesn't shift right all the time either. Took it to a mechanic and he says that all the engine sensors have coded at one time or another. And that the TPS sensor stays at low voltage all the time, and the brake switch on the master cylinder stays on all the time. Also I noticed the digital odometer is dim sometimes and go's out sometimes. It also will rev up on its own part of the time when at idle or just started it and wont go back down. Need help please, most mechanics around here dont want any part of electrical problems. Is there a way I can test the ECM or at least change it out with one from another vehicle to see if it helps. Thanks
Saturday, May 22nd, 2010 AT 10:58 AM

7 Replies

Tiny
CARADIODOC
  • MECHANIC
  • 34,403 POSTS
Hi ajcaldwell22. Welcome to the forum. Don't go blindly replacing random parts. That's the most costly, least effective way to solve a problem. The clue is the dim odometer display. That right there rules out the Engine Computer.

The instrument cluster is the most intelligent, (complicated / unreliable) computer on the vehicle. All of the other computers talk to it and need its signals to operate properly. Based on your observation of the gauges, start by inspecting the connector pins for the cluster. The symptoms you described suggest low voltage due to a poor electrical connection or a component failure in the cluster itself. You MIGHT be able to get a clue by loosening the cluster's mounting screws and lightly flexing the housing when the problem acts up. If flexing it makes it start working properly, look for loose terminals or other points that can be re-soldered. Be sure to leave the ignition switch turned off when unplugging the cluster.

Caradiodoc
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Saturday, May 22nd, 2010 AT 3:32 PM
Tiny
AJCALDWELL22
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Expedition has been running pretty good except a slight shifting issue, ( not wanting to downshift from 5 to 4, can push OD off to get it to) until yesterday when it finally went crazy again, OD light flashing gauges half way working, oil pressure light flashing, and would not shift as if it were in limp mode, finally I just pulled over and shut it off. Tried to restart and it wouldn't start. Let it sit for about 20 minutes and it started and ran fine. I did try flexing the instument cluster a little like you said, and the odometer light was definatly affected to the point it went out, but didn't help the car run better. I think I will pull the cluster out to check for obvious shorts, and see if I can find the grounds to it. Can the cluster itself cause all those problems at once? I did notice the ECU was warm to the touch after I shut it off.
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Tuesday, June 1st, 2010 AT 9:17 AM
Tiny
CARADIODOC
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Yes, the cluster can cause a whole bunch of seemingly unrelated problems. I'm not sure which year they started using a FEM, (front electronic module), but that and the cluster are BOTH involved with honking the horn. Two computers to turn on a ten-dollar relay instead of the horn switch that worked fine for 80 years! Also, if your vehicle has a GEM, (generic electronic module), check the connector for it. I read a lot about windshield water leaks on pickup trucks that cause corrosion on the connector pins. That module is the counterpart to Chrysler's Body Computer. It runs door locks, power windows, wipers, interior lights, stuff like that. If you simply unplug it, plug it back in, and the problem does not occur again for many weeks, clean the connector pins and module terminals. The scratching action of removing the connector can shine up a spot on corroded pins and make them make better contact for a while.

If you can catch it while the problem is acting up, use a cheap digital voltmeter to measure battery voltage while the engine is running. It must be between 13.75 and 14.75 volts. If it is low, the computers will do strange things. Computers get confused and do weird things when the power supply voltage is low.

Caradiodoc
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Tuesday, June 1st, 2010 AT 11:00 AM
Tiny
AJCALDWELL22
  • MEMBER
  • 3 POSTS
Problem has progressed, I took the Inst Cluster out took it apart, no obvious loose connections, good news is the odometer is working fine, no flickering. Took the PCM apart, no obvious bad places, The problem now is that the temperature gauge goes to hot and floods it out before I can try to start it, I can tell if it will start just by looking at the temp gauge, if it says hot, wont start, if it stays in normal range it will start. Also tried another battery in it, no luck. I un plugged the coolant sensor and turned the key on and it still goes to hot with light on, and I havent even started it yet. I noticed that the coolant sensor and TPS sensor are both in the same harness and both have coded but that wire harness goes behind the motor by the firewall where I cant get to it to check it. I also took the plugs loose on the fire wall that come from the fuse box in the engine comp to the inside of the cab and looked like moisture in it so cleaned it out and applied electrical jelly to it I thought I had it figured out, it ran for one day and now the temp is stuck on hot and it wont start again, tried taking plug back off and on again, no luck. I need to find a electrical trouble shooter to find this short, I give up I have taken this rig almost completely apart to no avail
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Monday, June 7th, 2010 AT 9:16 PM
Tiny
CARADIODOC
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With so many seemingly unrelated problems, one thing they might all have in common is loose or corroded grounds. A number of different circuits have their ground wires tied together in a single terminal that is bolted to the body. Look for those behind the left kick panel and under the hood.

Caradiodoc
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Tuesday, June 8th, 2010 AT 6:02 AM
Tiny
AJCALDWELL22
  • MEMBER
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Now i'm getting somewhere, . Maybe. I noticed that the temp sensor gauge would act up without the car running and the switch on, so I had someone sit in the car and watch the gauge while I wiggled and pulled on every wire I could find! Finally found that the plug to the ECU box by the battery affected it. After checking the grounds to it thoroughy, I come to the conclusion that it is in the plug to the ECU or the ECU side of the connection. There seems to be just a little bit of movement on the ECU where the plastic peice connects to the metal and flexing that will make it act up. The ECU gets pretty hot also. If I cant get this fixed, how do I go about getting another ECU? Can I get one at a junk yard to plug in to try? I heard they needed programed. I dont know how hard they are to match up. If it is not that then its in the harness plug. And it looks tough to get apart. Thanks for your advice
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Sunday, June 13th, 2010 AT 9:49 PM
Tiny
CARADIODOC
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I would ask the folks behind the counter at a local salvage yard about replacing the ECM. I don't think programming was an issue yet in 2000. I'm happy you found a way to make the problem act up, but I can't imagine how so many things could be affected all at once. It seems unlikely that a lot of pins in the connector are making bad contact or a lot pins in the computer have bad solder connections. Is it possible moisture got in the conector and there is some corrosion between a few pins?

Caradiodoc
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Monday, June 14th, 2010 AT 2:19 PM

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