2.3L ('02-'11) Sudden Misfire

[FiremanBob]

My '01 2.3 Duratec with 295K miles suddenly started misifiring last night and threw a code for cylinder 4 misfire. Today I took it on a 10-mile test drive with Forscan running. It misfired quite badly although the CEL did not flash. I tried to attach the Forscan log to this post but apparently it is not an allowed file type. Other than fuel trim which is around -6%, everything seems ok except the misfire.

The last three times this has happened since I bought the truck in 2017 it was the coil gone bad. Probably the same this time, but I'm posting in case something else might be at fault. It would be great if I could attach a Forscan log.

 

[FiremanBob]

I guess it's a boring question. Today I pulled the plug from cylinder 4 (which was the one noted in the DTC). It looked perfect. I am pretty sure the coil is the problem and plan to get a new one tomorrow.

Attached is a screen cap of the Forscan log I did this morning with the truck at rest in the driveway. The only anomalous reading was the short-term fuel trim which ran -5-10%. I think this could be due to the misfire causing unburned fuel to go into the O2 sensor. I'll know tomorrow anyway. I wonder what other items I should run on the forscan log to get a better diagnosis.

 

[FiremanBob]

Installed new coil pack. No change. Still misfires under load from 1800-2500 rpm. But while Forscan and I can both see and feel the misfire, it doesn't throw a code. Smooths out when I get the revs up. Still running rich. Now the mystery begins. Unless someone here knows what I should look for.

I'm going to start with checking for an exhaust leak, then try a compression test. I suppose changing the plug wires should be done to rule that out, but this set isn't very old - not more than 2 years and less than 10K miles.

 

[pjtoledo]

how is the oil consumption?
when my '05 hit hi miles the rings in cylinder # 1 started loosing compression and let oil by.
that started an occasional miss that got progressively worse.

 

[FiremanBob]

Thanks, pj. Oil use is <1 quart per thousand miles. I haven't smelled any oil in the exhaust.

I ran a compression test Wednesday. Results were:

1 168
2 170
3 160
4 164

I'm stumped.