no codes, doesn't run

[egvsuccess]

Last year, got a 2003 mountaineer awd, 4.0 6 cyl from New Orleans.
started having some intermittent miss fires at highway speed.
started showing code for fuel tank pressure sensor and the sensor test out at over 5 volts with key on, not running (should be under 3.) Then it wouldn't go over 2000 rpm and 37 engine codes showed up. Then it would run shortly, but load up and die.
Replaced ECU from another American Manufactured Explorer which took care of all codes except fuel tank pressure sensor. Same problem exists with loading up and dying.
Replaced EVAC line including the sensor and rewired according to instructions, voltage now at 2.6, but have the exact same problem with loading up. We are showing no codes with key on & engine off, but cannot get it to run long enough to run a code sequence and get another read out.
Spark plugs are sooted, but not a heavy buildup. Almost looks like they were spray painted black.
We would appreciate any suggestions. Thanks!

 

[arco777]

Might want to have a shop with a scan tool have a look. The scan tool can look at all the sensors at once and see if any are reading weird. A sensor can fail and give weird outputs to the PCM, and the PCM does not always realize that the sensor is the problem or even that anything is wrong. Comparing sensor values to known acceptable ranges would be a good start. You can do some sensor testing yourself with a multimeter and research into what the operating ranges are, but it is much easier to use a scanner and a tech who knows what he's looking at.

 

[egvsuccess]

Thanks for the reply. All that has been done, After replacing the ECU and the EVAP line, no codes are showing. Until it actually runs for a few minutes, it can't run the sequence to reevaluate. We are replacing the plugs and wires and will try to check for restricted exhaust with the short time it will run.
Any other suggestions are greatly appreciated. We were hoping someone had a similar problem that they solved.