Hello folks, I'm having a problem with my 2001 expedition, problem has been off and on for a long time, now its dead "Misfire on number 7" today I changed the cop, injector, and plug. Injector is not getting power, checked with noid light after I bought the new injector. harness is good, checked with volt meter from pcm connection back to connecter. Took old injector and plugged it into number 1 connecter, and it clicked like crazy, hook it back up to #7 and nothing. Does this sound like the pcm to you guys?

The old cop is good, and I am pretty sure the old injector is good, tested them both on the truck. I should have tested the parts before I bought new, but oh well, whats done is done, got some spares I guess..

2001 expedition
5.4
4x4
xlt
117,000 all stock

Thank you for reading this and any help you may offer

 

Check the harness and the plug connector for the injector. If everything else works when moved then its a wiring/connector issue.

 

Harness is good, ive checked it from the plug back to the pcm connection, resistance was also under 5 ohms on the wire.

 

The #7 COP pink wire goes back to the PCM. The #7 COP red wire should have +12v to ground on it with the key on. Does it? Tip: the COP red wire is common to all 8 COPs.

The #7 injector tan wire goes back to the PCM. The #7 injector red wire should have +12v to ground on it with the key on. Does it? Tip: the injector red wire is common to all 8 injectors.

 

you got me on that one, i'll check them tomorrow All i checked was continuity and resistance Thank you, Alloro

 

Cop and injector have 12 volts Hooked the noid light back up to recheck and discovered that the #7 injector is getting a pulse for the first 4-5 seconds after engine start up, then it shuts #7 down. The other injectors fire normal. It will also pulse once every 5 seconds or so

 

As difficult as it might be, it would rig a jumper wire from the pin/connector at the PCM for the #7 injector, run it to the noid light, then run +12v to the 2nd side of the noid light. If the noid light acts the same as when it's connected at the injector I'd say bad PCM. If it flashes steady then I'd say wiring harness intermittent connection.

 

Thats a good idea, I have the ecm out now so making a jumper wire would be less difficult, i'll get everything set up and test it again then post results. Thank you again Alloro

 

Well bypassing the harness altogether has the same results Crank sensor or cam sensor maby? If it was those though, I would think my problem would be more random, thinking out loud here so to speak...

ECM injecter circuit fault is what im leaning towards now. Thanks for all the help so far

 

Ditto. If it were the crank or cam sensors more than just cylinder #7 would be affected, all of them would be.

 

I have a ECM on the way, I will post results after the dealership has reflashed it, and with luck will conclude this thread.

 

update

new ecm and flashed by dealer problem still persists. When truck first starts it flashes noid light when rpms drop it kills injector. Im out of ideas

 

I suggest doing a compression test on cylinder 7, seems the pcm is shutting off the injector because its detecting a misfire, this is done to prevent cat burn up, if cop is good , good plug , injector , voltage pulse on cop, etc. look for the other misfire issues, head gasket, valve not seating, rocker issue

 

New update - keeps getting stranger

checking the cam sensor I noticed while it was unplugged the injecter would fire as normal! Ahha, I found it, I go to the parts store buy new sensor, install it, plug it in, guess what same problem injector still dead. Im getting very frustrated at this point.

 

problem solved turned out the connector inside the new cop was broke.. Noticed it when I pulled the plug to do a comp test... Thank you everyone that helped out.....