So as you can see from my signature line, I did a lot to my engine. After I got it running a few months ago, I have been tracking down and repairing one issue after another. Some days, it runs like a champion with no issues whatsoever. . . the engine runs smooth as a sewing machine; it sounds amazing; has tons of power; better than I hoped for. But some days, it almost stops running and I have been banging my head into the wall trying to figure it out. Here are the symptoms:

1) It began having an intermittent rough running a couple months ago. It would start normally and run normally for a while but then it would start missing and "hiccuping"/stuttering where I felt like I was being jerked forward and backward while driving and the engine suddenly loses power and begins having detonation chatter under even the slightest throttle. Sometimes after turning the truck off for a couple minutes it will run normally after that and sometimes it won't. Most times this occurs after the engine is up to temperature, but sometimes it begins before it is even warm. Engine is not even getting close to overheating, no CELs, and not throwing any codes at all. When it runs normally, it runs well at light throttle and WOT with no detonation/pinging whatsoever; just smooth. Thought it might be water in the gas. I dumped the tank and refilled it with gas from another station and flushed the lines -no dice. I then replaced the crankshaft position sensor, camshaft position sensor, and throttle position sensor. The problem persisted.

2) Not long after the intermittent rough running began, it started exhibiting starter kickback which is a dead giveaway for crossfire. I used the Dodge TSB and re-routed every plug wire at least 2 inches away from each other. Starter kickback stopped. Intermittent rough running persisted.

3) Two plug wires were getting too hot from being encircled by a vertical header tube loop (shorty headers) and causing the coil to get too hot from resistance. I put high-temp insulated sleeves on the plug wires. Plug wires are not getting too hot, but the coil wire is still getting firecracker hot at the boot where it connects to the coil. Intermittent rough running persisted.

4) I noticed while it was idling smoothly in the driveway one day, it made a "blub" sound and the rpms briefly dropped and a single small puff of black smoke came out of the exhaust (the truck does not smoke). I believe that is a single cylinder flooding event where the fuel air mixture in one cylinder was too rich to ignite. It continued idling normally after that. This gave me a theory: if an intermittent sensor or electrical issue can incorrectly richen the A/F mixture in a cylinder to the point that it won't ignite, it could also make it way too lean (which could explain the detonation chatter at barely any throttle on an engine that normally doesn't detonate even under WOT).

5) Yesterday, I drove 190 miles without the slightest hiccup. Engine was powerful and smooth. Today I started it up to go to work and it was running rough before I even got out of my neighborhood.
Any thoughts would be really appreciated.

 

You have an intermittent failure on one or more of your critical sensors. What brand are the cam, and crank sensors? Do you have the ability to do data-loggin?

 

The new crankshaft position sensor is a Delphi. The cam sensor (distributor pickup coil) is Standard Motor Products. I have an Innovate LM-2 wideband O2 datalogger that I can use.

 

Think I would run some logs, one when it is running right, and one when it's not.... see what changes.

 

Sorry to resurrect my old thread, but sorting out my intermittent misfire issues had to go on hold for the last year due to having another baby and finishing up school. Hope this is ok, because my first post in this thread really gives a thorough background on my truck's problem and I thought we'd just pick up where we left off.

As mentioned earlier, this is not a mechanical issue but some kind of electric gremlin. A genuine intermittent that doesn't throw any codes -and those are notoriously difficult to track down. Neither the AutoZone rental Bosch scan tool nor my AutoEnginuity standard OBD-II scanner picked up anything anomalous -even while the engine is misfiring heavily, so I bought the AutoEnginuity enhanced Chrysler suite that allows me to read every sensor in the vehicle. It has over 100 different parameters it can measure, but I can only monitor 9 at a time, so I need some help choosing what to look at since the standard parameters look normal during the misfire events.

What should I monitor for my next run?

 

Fuel trims, ignition advance, fuel sync, if you can...... tps, ect.....

 

So I logged some data from my truck one day when it was running perfectly and I logged a day when it was misfiring and running rough. Here's what changed: On the good running day, the AFR would hover around 14.6-14.7 during idle and light throttle, richen to 14.4-14.5 under light acceleration, and richen to 13.5 at WOT. On the bad running day, the AFR hovered between 14.6-14.7 when I started the truck, but two minutes later, it went to 14.8 and stayed there. No matter what I did, it didn't budge from 14.8 for even a split second; idle, light throttle, WOT, it didn't matter. Does this sound like an O2 sensor issue?

 

Yep. Did the truck ever get into closed loop?

 

No, it didn't.

 

Need to find out why. Could be engine temp, could be O2 sensors not ready, or a few other things I just can't think of right now.