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Random codes, sensors changed, ECM rebuilt, still runs badly.
SES comes on, o2 sensor bank 1. Changed, fixed. New plugs put in a few weeks later and it starts idling rough, so I changed the wires, still rough. Went back with Motorcraft plugs, acted a little better, but not for long. SES came on, getting lean and/or misfire on bank 2. Problem: downstream o2 sensor. Clear codes, they come back. Same problem, even worse. Upstream sensor. At this point, I know what I must do, just change ALL the sensors. It just hit 80,000 anyway so might as well. I have changed plugs, wires, 4 O2 sensors, MAF sensor, fuel filter, and it just gets worse. Truck dies immediately after starting. Runs OK with a rough idle after a warm-up. Last code said possible faulty ECM.
Took it to a highly recommended mechanic. He agreed. Sent ECM for test, problem found, fixed, got it back, starts and runs great. Kill it and as soon as it's restarted it throws random codes. Clear the codes and it starts fine, kill it and it throws a whole different set of codes.
Random codes every time. MAF Sensor, o2 sensors, possible faulty ECM, lean and/or misfire condition both banks, any code you can think of, that's the code I'm getting. Clear the codes and the next time the SES light comes on I get a whole different set of codes. ECM was rebuilt, just got the truck back today, waiting to see what the diagnostic cycle comes up with.
**UPDATE** OK so it drove great all the way home, this morning it doesn't want to start without mashing the gas, spits and sputters and coughs until it warms up. Less than 50 feet from the driveway and SES pops.
Took it back to the shop and spent 1.5+ hours with myself and two techs going through everything we can think of. All wiring and harnesses, connectors, clips, sensors, valves, and controllers seem to be fine. Fuel pressure is within specs, no intake leaks, changed a short piece of hose that was rotting away at the pcv valve, but found nothing out of range of Ford's specs.
It was suggested that possibly the back-flow valve in the fuel pump is failing. Going to try priming it a few times before starting in the morning sto see if an empty fuel line may be the problem, although I am starting to doubt it.
Last edited by Stevil; 05-02-2012 at 10:00 PM.
Random codes every time. MAF Sensor, o2 sensors, possible faulty ECM, lean and/or misfire condition both banks, any code you can think of, that's the code I'm getting. Clear the codes and the next time the SES light comes on I get a whole different set of codes. ECM was rebuilt, just got the truck back today, waiting to see what the diagnostic cycle comes up with...
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