97 expedition 5.4 stumble at 1300 - 1500 rpm

[James Meyers]

Engine stumbles when slowly accelerating. When I reach 1300 rpm egr valve lifts off its seat. Continues stumble thru until I reach 1500 rpm. Egr drops back on it seat and it smooths out. New egr. (Old one had a leaking diaphragm). New backpressure transducer. No codes are thrown. Ecm is signaling vac relay to allow 3 in vac to egr at 1300 to 1500 range then drops off. Just annoying. It idles, starts & runs great other than this. O2 sensors check out fine on scanner. Coolant temp 190. Doesn't do it in open loop.
This is my first post. Take it easy on me guys. I'm new at this!

 

[MikeA]

Take a look at your
MAF (mass air flow ) sensor, might need cleaning or replaced.

But first make sure there is no air leak between the MAF and the throttle body, if there is a leak, this will cause problems, there should be zero leaks in area just mentioned.

MAF sometimes , gets over looked as a possible problem, because it will not always throw a code out, but will cause hesitations and make the motor feel like its dumping power.

To clean MAF , spray it with CRC brake cleaner.

I dont remember the specs on testing MAF, shouldn't be hard to find on internet, or someone here knows .

 

[James Meyers]

Thanks Mike for the fast response. I will definitely try the MAF cleaning and get back to you. Have checked for vac leaks but not the air intake. Will add that to the list. Thanks again for your time.....

 

[Mr67Stang]

watching...

 

[James Meyers]

Hello again! Just did a thorough inspection of air intake ducting for leaks and connection status. It's in good health. Did test to confirm status of the MAF sensor.. The voltage and ground test are good. Voltage at operating temperature at idle is
. 954. At 1500 and 2500 voltage is in spec. and moves smoothly through rpm range. I hope you have some more good suggestions on further testing as I'm at a brick wall.

I'm not sure why ECM is sending a signal to the vac regulator solenoid at 1300 rpm then drops it at 1500. Something is talking to the ECM feeding it bad info.
I've been swearing at it. ( hasn't helped)

Any and all suggestions would be appreciated!

 

[MikeA]

inside the throttle body there are two small ports from the EGR valve. these ports may be clogged up with carbon, open your throttle up and if its all black inside, remove throttle body and clean, specially the 2 small port holes to the egr.

Have you tested the egr vac solenoid?
Has your check engine light come on, if so what codes show up?

 

[James Meyers]

More info. For thought...
Tested vac solenoid ohms. Looks good. Did vac test with tee in vac line while driving. My testing source said I should see 5 in vac under acceleration. Only have 3 in. vac. Not sure if it's a faulty solenoid or my Guage. Hate to sling more parts at it if I can narrow it down to one thing.

Still TESTING in TEXAS......

 

[James Meyers]

Sorry I missed your post Mike.
I have removed the throttle body for inspection earlier when I found the faulty egr. Port is clear. Did a thorough cleaning of the throttle body at that time. I have done a lot of testing and checking before I ever posted on this forum. I am running out of ideas.
I know people on here are alot more knowledgeable than me. I really appreciate the fact there are people like yourself that share your time and knowledge with a guy like myself.
Forgot to mention that no codes displayed

 

[MikeA]

Ok, just seen your post

Did you test the egr itself?, had to reread original post, you replaced egr already

 

[MikeA]

Found this link, lets see if it helps us

http://easyautodiagnostics.com/ford/4.6L-5.4L/how-to-test-the-egr-system-1