I've been dealing with various engine codes all relating to cyl 6. p2317 and p0616 I think. Ignition coil insufficient ionization and misfire on 6. Replaced the coils and no luck, replaced the spark plugs and unplugged the battery at the same time and it went away for several hundred miles. I celebrated, danced in a little circle and thought all was well.

Then I encounter a sequel "The Code and Crappy Idle Return." Check engine light comes on during my usual 5am commute to work, I pull over and check the codes to make sure p999999 "Your truck will detonate in 30 seconds" wasn't coming up. Codes were P2317, 2 B codes for Battery voltage high and Battery was disconnected as well as the usual washer motor voltage high code. I cleared the codes and went on my merry way hoping it was a blip.

Well today the code came back AGAIN for a trilogy much like the Chucky movies. The truck was running much like an old school tractor, I shut it off and restarted it and babied the truck home. Misfire on 6 code as well as intake air temp sensor high voltage. I returned the ECU to stock with my superchips programmer, codes went away, and did a 100 mile or so round trip.

I'm now awaiting the next round of codes. Does this sound like a problem with the computer or should I start checking compression on 6 and replacing injectors as those are the last 2 things I can think of that could effect the same cyl time after time.

 

I wonder why that IAT sensor is acting up with cylinder 6. Could be completely unrelated to eachother but who knows. High voltage so then it has an open circuit? I would rent or buy a compression tester like you insisted. Just remember that all plugs have to be removed to do the compression test..which is annoying!

 

It could just be a single sensor. On my wife's 2006 Durango, the oxygen sensors being faulty caused a intermittent misfire on cylinder 4 code. Replaced the front O2 sensors, "reset" the computer's learning curve using the SCT tuner, and never had it return.

 

I just thought/think it's weird I keep getting random other codes that go along with the misfire but they only show up once and then once the codes are cleared all is well again. I will have to do a compression test this weekend.

 

Chances are that you have a misbehaving sensor, intermittent connection somewhere, or a poor ground connection between the engine and battery. I'd start with the connections to all the sensors and the computer, check them out, clean as necessary, and then use di-electric grease on assembly. Next, I'd look for test specs and procedures for each sensor and get ready to check them out if the plug and ground investigation proves futile. It's a matter of logical, systematic debugging rather than a shotgun approach. You may find something with a compression test, but I don't think you will - you'd have the problem constantly, a compression problem doesn't appear and disappear.

Look at whether the problem manifests itself when the engine is cold or is it after it's somewhat warmed up, then, if it runs OK cold, check the list of sensors in the open & closed loop configuration - one of the sensors that comes into play when the engine warms may be providing a sporadic or erroneous signal to the computer.

Another thing that's crossed my mind is whether you've "poached" anything with the e-fan hookup. If there's any place in that circuit for the back emf to go when the power is cut to the fan motor, it can fry electronics that are normally up-stream from it - that's why I always put protective devices on any inductor I install to prevent an inadvertent component toasting.