91 Ex with miss while accelerating

[Syko]

1991 Ford Explorer Sport. 296k

Has a miss while accelerating, and a rough start in the mornings.

First start of the day the engine fires right up but shakes for a good 30-45 seconds before it calms down and I can drive.

Traveling at highway speeds or up hills is when I notice the miss the most. It seems like I can only push the throttle so much before it starts missing, I can back the throttle off and it will continue fine.

No CEL

Ive cleaned the IAC, MAF and replaced the fuel filter. New spark plugs all gaped correctly and sp wires are 3 years old.

Possibly fuel pump or ECT sensor?

Help!!!

 

[SenorNoob]

"First start of the day the engine fires right up but shakes for a good 30-45 seconds before it calms down and I can drive."

AND

"I can only push the throttle so much before it starts missing, I can back the throttle off and it will continue fine"

Sounds like the computer is having a hard time in open loop. So much so that it's running rich(or lean!) enough to miss. Have you put in different injectors?

 

[Syko]

Thanks for the reply,

I havent changed the injectors, engine is pretty much stock. No leaky injectors either she wouldnt start with full throttle, not a blip.

I just tested the TPS and it came back within spec.

 

[TxGasRacer]

http://troubleshootmyvehicle.com/ford/4.0L/how-to-test-a-misfire-1