2 Different Mechanix STUMPED!!! | Page 2 | Ford Explorer Forums

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2 Different Mechanix STUMPED!!!

good call on the test drive swap!

where is the computer located on the vehicle?
 



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The engine died when he disconnected the vacuum line from the pressure regulator? Try that again, now. Mine won't die, and I bet that is a symptom of the problem.

When you disconnect that line, the pressure regulator should raise the fuel pressure(throttle), and you have a vacuum leak. That fuel pressure should be many psi greater than the off-throttle pressure.

Check for disconnected vacuum ports, check for leaks.

A PCM is a non returnable part, at Ford. Junkyards are a crap shoot, because the used part you get might be bad. LOL,
Don
 






Yeah I know I eneded up going to the better business bureau to get my refurbuished PCM replaced from Ford because when I bought it I asked about the warranty and they told me 90 days from time of purchase, it failed in 40 and they refused to replace it because they said my truck was "modified" well no kidding they knew that when they installed it.
I have been running a junk yard PCM that cost me $35 for over two years now....

the PCM is simple to get to, its under the passenger side plastic kick panel under the glove box, 3 screws hold the mount in place, a single 10mm botl holds the wiring harness to the PCM, you may also have to undo a ground wire to get enough slack to work on it.

Check for vacuum leaks first, it is common for the early 4.0Ls to have lower intake gaskets leak, sometimes you can get by with just tightening the lower intake bolts.
If all the vacuum hoses check out, including the one that goes to the vacuum modulator on the transmission, use the starting fluid method witht he engine running to see if the lower intake is leaking.

Again I bet your PCM is bad. :), based on what tests you have done so far and your symptoms
 






dang it, i had this long reply about fuel sync and ignition timing written up, then I saw that it doesn't do it while in park.

what I suggest is finding a Factory service manual. Find the section on the PCM and start reading the various loop modes. It should tell you exactly what sensors and systems are monitered while in park Vs while in drive. Find the differences and check those sensors.

it personally sounds to me like you're massivly retarding the spark timing.
 






Hey I know this is going to sound weird but I would try. I had the exact same problem with my 92 sport, no acceleration, real jerky when you press the gas, it came and went for some time untill it was all the time. I spent 2 weeks trying to figure this out, i did a tune up all but the wires. It was still there untill 2 weeks later i put the Motorcraft wires on the Truck and Instantly cleared up the problem. so try it i think the wires were 50 bucks. BUT THEY MUST BE MOTORCRAFT. No after market.
 






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