4.0L missfire problem

[almostclueless]

Compression check.....or cut to the chase and SAVE money by getting a diagnostic done by a good Ford garage.

 

[Little Egypt]

I replaced the coilpack less than a year ago.

I guess I'll have to take it to Ford, because I'm all out of ideas.

One last thing, this morning (after sitting overnight) the truck didn't start to misfire until the engine started warming up. Obviously, while the engine is cold the PCM sends more fuel to the cylinders (choke) and then leans out once the engine is warm. Since the codes are coming back as lean mix and I'm fine while cold, I'm leaning toward injectors.

Cheers,
Aaron

 

[Little Egypt]

I decided that it could be low fuel pressure (and thus probably a bad pump). Fuel pressure was good (65psi) and I was back to square one, so I took it to the dealer yesterday.

Ford charged me $80 to pull the codes and tell me it was a lean mix code. They also said it was probably an O2 sensor causing the lean mix. They said it was the left one (which is the one that I had changed last year). They wanted another $210 to change it ($100 for the sensor, $110 for the labor). I went to Advance and bought both sensors (just to be safe) for $90 and had a local shop change them for ~$80. No problems yet, but I'll have to wait and see.

Cheers,
Aaron

 

[Little Egypt]

200 miles and no problems. Looks like it was the O2 sensors. I'll check milage over the next few tanks and report back, but it seems like everything is back to normal.

cheers,
Aaron