97 expedition 5.4 stumble at 1300 - 1500 rpm

[MikeA]

Test TPS (throttle position sensor)

I can not think of anything else to check, leaves me pointing to pcm/ecm may be the problem, if not bad connection someplace.


Tossing this one out there, try clearing pcm, or if you are lucky like I am and have a junkyard near, to get a used one cheap for testing

 

[James Meyers]

Thank you Mike.
My 97 is the same as your 98.

That is the link I've used to diagnose my system.
Went through each step carefully on each device. Even double checked the backpressure transducer. Everything tests OK. That's what has me stumped. I keep going back to the ECM signal to the vacuum solenoid at 1300 rpm. Why am I getting a signal?
Wondering if ECM is faulty. Been told they don't go bad very often. Usually something is telling it to do whatever.

 

[MikeA]

Try clearing pcm , get a cheap used one from junkyard for testing, can not think what else could be problem.

I am pointing at pcm or loose wiring.

 

[James Meyers]

Latest update!

Checked TPS as per one of your last post. Found a gap in signal going to the PCM. I'm hoping this cures my problem. Gap in throttle movement is near WOT. Stumble is lower in rpm range but still could be the culprit.
Will keep you posted. Just ordered one from Rock Auto. Be here end of week.
Thank you again for your time Mike. YOUR THE MAN!

 

[MikeA]

I hope that fixes it for you!

 

[1997SCEBFEX]

I've replaced the TPSs twice in almost 20 years (purchased May '97). it does get memory especially that rpm range for a lot of roads I drive.
hopefully it's your huckleberry.
Let us know.

 

[James Meyers]

I am glad to announce that with the help from the guys on this forum that I have solved my problem. Received a new TPS today. After instalation and test driving confirm that was the culprit. I can't explain it but my fuel trim numbers are closer to being neutral than before. Idles and runs better throughout rpm range.

Not only did I solve this problem, I got an education regarding the engine control system.

Thank You for your time........

 

[MikeA]

Glad your all fixed .

Thanks for coming back to post problem solved