Recently picked up a new to me 2000 Ram 1500 5.2L after my brother totaled the 2001 it had an occasional misfire on cylinder 5. It had factory ignition components on it so went ahead and started with a tune up new cap and rotor, plugs and wires. When i went to remove the cap I found the mounting ear on the distributor housing was cracked/broken so went and dropped a new distributor and inductive pickup in along with the tune up, reset the pcm, and set the fuel sync at 0. Now this misfire is constant and there is a light almost rhythmic backfire in the exhaust. I then went and tried to pull any codes and none were present. So I rechecked all my wire routings and firing order at the dizzy using the reroute tsb diagrams and so forth and all looked good. So I figured I'd hop on here and put out some feelers before a bring it back in the shop after work tomorrow and dive deep into the diag.

 

If it is close to or over 100k, change the crank position sensor... cleared up my random fire issue.

 

Checked the CKP and CMP signals and checked there trigger counts with scanner they both looked good

 

Do a compression test. Either that, or Cylinder Leakdown. See what the numbers say.

 

Do the trigger counts tell you is the sensor is detecting early or late?
My theory on aging CPS is, the sense window gets wider as it deteriorates, meaning the trigger could be a few degrees early or late, trowing off spark timing.
With other sensors failing, there is usually a fail safe value for the ECM to work with, secondary symptoms, and/or fault-finding paths.
With the CPS, it is either working or not, as far as the ECM knows... there is nothing to back it up, or to say it that it is working correctly.

 

If none of the above work check the fuel supply. A lean or rich fuel mixture can also cause backfiring/misfiring.

 

Spillage I assume your talking about the Crank position sensor I already replaced the CMP sensor. I'll toss a new one in and see if anything changes. It has 96k on it with a lot of factory parts, so it couldn't hurt. it was an auction truck So it sat for awhile. I pulled off my new wires and resistance tested for ****s and giggles and looks like I got a crap set found to bad wires, last time I buy autolites.

 

If you have a new factory CPS, you should be good, unless it got damaged.
After ~75k any sensor is potentially going to be a suspect.