5.9L rough idle, running rich?
 

hello everyone. i'm new here, and i have a 98 dodge ram 2500 with the 5.9L v8. recently it has been having a rough idol problem, and it tries to stall on me in the middle of intersections sometimes. if i shut it off then start it up again it runs fine for a little bit, then starts idoling rough again. i plugged in my code reader and i have been getting a bunch of different o2 sensor codes, usually po132 and po138 (bank1 sensor1 high voltage, bank1 sensor2 high voltage) and po135 (sensor 1 heater circut malfunction) so i replaced both o2 sensors but its doing the same thing. the codes don't always come up, just every once in a while. i removed the air cleaner and started it and it idols great without it, so i cleaned it (knn filter) and it's STILL running rough. for some reason it's running rich, and starts to suck in a lot more air which is when it starts idoling rough. my dad thinks it could be a vaccume leak or bad pcv valve, anyone have any imput?
thanks,
Will

Check your plenum. :D

yea i did the plenum gasket when i replaced the engine. and correction, i meant to say pcv valve, not pcp :icon_bricks:

Aftermarket PCV valves don't always have the correct flow rate. Get one from the dealer. Less than eight bucks.

Clean the throttle body. Disconnect the battery, remove TB, take off IAC valve on the back, and clean ALL the passages thoroughly. Reassemble, reconnect battery, fire it up, and see if it is happier.

And you need to figger out why you are getting the O2 codes, and fix it......

the throttle body was cleaned when i replaced the engine also. i checked my pcv valve and it seems to be working fine. i must have a vaccume leak, it's definately running rich, which i think is why the o2 sensor codes are coming up. idk, im stumped. what is the best way to test for vaccume leaks? thanks for the imput heyyou

Hmmmm..... whats fuel pressure look like?

As to vacuum leaks, a key spot on these trucks is the cruise control motor--which is conveniently located under the battery tray.

Also check the spot where all the vac lines tie together on the pass side of the block, kind of behind the intake (exact directions, I know).

I'd think you'd be having the "wild vents" issue if a vac leak was to blame however.

what exactly is the wild vents issue?

When driving with the a/c or heater on, giving it gas switches blower output to the defrost, then back.... or some such. Never dealt with it personally, but that's the idea i get from other's descriptions of it.

Do a search for wild vents... there's a thread that comes up with many pages that has a lot of good info on chasing vac leaks. I believe sheriff420 is the op of the thread I'm speaking of.

EDIT: this is the thread I'm speaking of https://dodgeforum.com/forum/2nd-gen...ild-vents.html

Are you still getting the O2 sensor codes?

If so, which code(s)? If its just the Sensor 2 code, you may have a bad/clogged catalytic converter. Sensor 2's sole purpose is to check that. Only reason it'd trigger a code is if the sensor itself has failed, or the converter has failed.

What brand/model of sensors did you use?

i used bosch o2 sensors, and im getting codes po132 and po138, which is bank1 sensor1 high voltage and bank1 sensor2 high voltage, so my truck is running rich.. and ohh i'm not sure if the vent thing is happening to me, ill check. thanks!