I have tried to get the check engine light off for a week after getting cylinder 5 misfire code. It's a 5.9l with 130k miles
The engine idles ok and there are no apparent misses at higher speeds
1. I replaced spark plugs the wires and cap and rotor. Double checked to see the plug was sparking Not fixed
2. I replaced the fuel injector The light went out and came back after 15 miles. The new injector is making the right clicking sounds while running.
3. I used butane to check vacuum leaks everywhere including Intake manifold at the cylinder #5 intake Nothing detected.
4. I had cleared the codes let it idle 640 rpm until the code returned and recorded a snapshot- manifold pressure normal 5 psi ,short term fuel trim 0.8 , long term fuel trim 0.0
5. I did a compression check cold dry reading 125 psi and holding same with a wet oil test. Other adjacent cylinder # 7 is 130 psi
UPDATE just did a warm compression check all cylinders read 140 psi



Any ideas after all of this effort with no results?

Thanks in advance

 

Is the crank sensor still the original one? Or has it been replaced? (much easier on a van......)

Has the distributor ever been moved?

What brand/type of spark plugs are installed?

 

crank sensor is original and the distributor has not been moved the plugs are autolite. the plug is sparking.
i just did a warm compression on all cylinders they are all 140 psi

 

Ok, everything is as it should be, but, it still doesn't seem to wanna work right..... IS there an actual miss, or could this be the PCM misinterpreting something? Does it run smooth? Idle nice??

 

Not always idling perfect. Runs good on acceleration

 

What is manifold vacuum at idle?

 

manifold pressure was normal 5 psi

 

Huh? There shouldn't be pressure.... unless you are supercharged.

 

taken from a freeze frame report at 640 rpm idle

Intake Manifold Absolute Pressure : 36.0 kPa, 10.6 inHg
HMM NOW I'M THINKING LOW VACUUM CAUSED BY INTAKE MANIFOLD LEAK?

 

Yep. That would be a good starting point.