Okay all, still have misfires on a 3.9L #1 and #5 and sometimes a stall. All sensors have been replaced. 250K so I tore the head off and replaced with a used but reground all the valves and checked guides, springs etc. No change so I'm wondering what the next plan of attack might be. While in the vehicle, replacing the head check distributor movement relative to crankshaft movement and there is none. No play in the distributor. PCM was replaced but no resolve. Not all the time does it do this, intermittent. Fuel pressure and injectors all check out fine. Any ideas as what to check next, open to input. The only thing I can't do is replace the PCM with a new one because they don't make them anymore. I'm kinda leaning toward this since I believe I covered everything else unless I missed something. Anyway, thanks in advance on what you gearheads might think....sell the truck "or" continue on? Truck still runs strong so it's hard to give up.

 

Question: did you replace the O2 sensors?

 

Yes, 02's have been replaced a few times actually, just to make sure. I stopped at a truck place and talked to one of the guys there, explained everything. He told me to eliminate the cat, he does a lot of trucks with problems on one side of the engine? I found out some testing techniques as well such as temperature readings and monitoring voltages on the 02's to tell if the cat is not doing what it is suppose to do so, I will look at this first before temporally bypassing it. I literally did everything else. I did replace the cat about 5 years ago. I know you asked me about the 02's and like I said I replaced them but I guess if the cat is not up to par it could effect the way they operate? Thanks for the reply....if I ever find out what it is I will be sure to post since it seems like I'm not the only one faced with this issue. Too curious to give up now.

 

Have an update. Although the crank position sensor was replaced, apparently defective. I started all over again with the sensors and this sensor is the hardest to replace so I saved it for last....lazy on my part. New parts guys, they suck and are NOT dependable. Anyway, many people said here crank or cam sensor and they were right! This one had me fooled!