Hello everyone,

I need some advice. I have a 1998 ram 5.9 has 111k miles. I have put new spark plugs, wires, Cap, rotor, coil, map sensor, iac, TPS, Valve cover gaskets, all new fluids, and just got done with plenum repair all new vacum lines and upstream o2 sensor. I have a bit of a rough idle and it had it when I bought it a couple months ago. Can’t figure out what it is. Did compression test and leak cylinder test and all checks out great. Could the downstream o2 sensor be the problem? I also have no cat. Can’t figure this one out. Any help would be greatly appreciated. Thanks

 

Downstream won't be the issue, it really doesn't have much of an effect on fueling. It's just to monitor the cat. What brand front O2 sensor did you put in? If it's a bosch, that's likely part of the problem. NTK or Denso O2 sensors only please.

 

Yeah I put NTK.

 

Ok, so, that shouldn't be it.

Do you get any codes for misfires? Can you check misfire counters? See which cylinder(s) is(are) the issue?

 

no codes. Misfire counters?

 

Yeah, need a fairly billy scanner that can read data. Misfire counters should be listed for each cylinder. (assuming the PCM can count, the one in my truck sure can't...... I had a DEAD miss, that NEVER set a code.)

 

hmm ok. Im gonna look more into that and see if I can get a good reader. What about the purge solenoid would that have anything to do with it? Thanks

 

Maybe if it is stuck open, which would essentially be a vacuum leak.

 

thanks for all the information. I’ll let you know what I find. Gonna check the purge solenoid tommorrow and see if I can get a good scan tool to count the misfires.