ok, i've posted other threads with little help so i'm hoping i can get some help on this one. i'll try my best to explain what is going on here and see if anyone has any ideas.

truck does it when up to normal operating temp only. i'll drive it, stop, and throw it in park, then the engine has a real rough idle with a misfire intermediately. but if i rev it a little it seems to go away or even if i put it in gear so there is that little bit of load on the engine then it seems to also go away. there are no codes and not even unusual smoke when it misfires. what's goin on guys?

 

Have you changed your fuel filter lately?

 

You're not going to get a good answer to this - I know, I've tried for over a year now. I have pretty much the same issue, and so do some others here.

I've replaced air and fuel filters, all sensors, injectors and tubes, turbo, lift pump and fuel lines, VP-44, diagnosed both DC and Cummins computers, diagnosed the timing box, electrical lines and harnesses, resoldered connections, cleaned out the intercooler, adjusted the valves, etc.

Problem persists - a rough idle and a slight miss after warm-up that gets worse as the ambient air temperature goes up, but disappears completely at 900 rpm and above. Power is good, fuel economy is good, smoke level is appropriate to injectors, turbo, and box, etc.

On the other hand - if this thread yields a good answer, I'll be very, very happy.

 

Possible fuel leak letting a small amount of air in? Just a shot in the dark.
CJ

 

Are you sure there are no codes?

The symptoms you describe sound like a crank position sensor, but I believe they did away with that on the O2's. Try the cam position sensor. Unfortunately it is behind the VP up near the front of the block and I'm not sure it can easily be changed with the VP in the way.

Let us know what you come up with.

 

Your right, it does sound like a CPS. Some of my gauges were irractic also.

Dave

 

you can change it but it's not fun getting it out is the word---chris

 

This is a good point....are you just doing te key on/off trick or actually using a code reader?

 

Your rough idle is probably from your Jammer 3”s they tend to give a bad idle.

 

My rough idle occurred before I installed the J3's.... The list I gave were things I've done since I first noticed the condition.

There's been at least a dozen threads by different people on this issue in the last six months - all with the same problem, all with trucks in the model years '01-'02. That problem, in all cases I'm talking about, has -not- been eliminated by the "normal" diagnoses - filters, VP-44, fuel pressure, injector problems, sensor problems, etc.

 

well i just got back from precision diesel, (the place where i bought it) they used a scanner and performed an injector cut out test, and most everything seem to be ok, they found one code, you know the ECM calibration failure or whatever that's normal with a smarty. so, next tuesday night i'm supposed to take it back so they can check it out more thoroughly wednesday. they are suspecting that something in the pump was screwed up during calibration or either its just a factory defect part. but they're gonna check the pump, the wires going to the pump, and the ecm as well. and they said if its the pump then there'll be no charge.

to be continued...

 

It is interesting that you say that the idle smoothes out at 900. Mine bucks at 1100 to 1275. I was going to say weak injector till I read further. Were they pop tested before they were installed? Sounds like an electrical or electronics problem. Has anyone changed the PCM ? After changing the ECM that cost did me in for quite a while. Problems like this have the dealers use the drb ( Is it the PEP module? ) with the drb. This will and can show what the signals and voltages look like . Since everything is controlled electronicly.