I purchased a 2000 Dodge Ram 1500 V8 5.2 L Automatic 4 door cab without muffler and tail pipe and missing upstream 02 sensor. The engine wasn't able to rev more than 3000 rpm with check engine light on indicating the O2 sensor, so I replaced both O2 sensors (Upstream & Downstream) changed all new spark plugs, distributor cap, rotor & spark plug wires, muffler and tail pipe, then engine rev up-to 4,500 rpm. Next day when I started up and heard some whistle noise in the engine area. I took the truck to the gas station to fill up gas it ran fine but after running for awhile engine lost power in gas pedal, rpm dropped then struggles to rev after 3000 rpm and stared stuttering too even at full gas pedal down, not moving. Check Engine light came back with P0138 & P0171 codes. Today I started the engine, heard whistle noise. Moved around slowly, and left the engine on for a while. The Check Engine light went Off, No Engine Light checked by the key trick for codes. I pressed the accelerator and it still revs to 4500 rpm and after a while it started to drop 3000. Not sure whats wrong.. Is MAP sensor or the plate below the distributor cap has something to do with this issue?

Please advice the cause of this problem! thanks

 

Sounds a lot like a cat that is clogging up. That would explain why the front O2 was removed.......

Read thru the plenum thread stickied at the top of this forum. Lots of good info in there.

 

Thank you for your reply, I checked out the plenum area below the throttle body. And I found some trace of oil underneath. It’s not flooded with oil. Please can you review the pictures and advice. Please guide me through

 

That doesn't look good.... (plenum) I would be tempted to pull the throttle body, and have a look... see if there is oil at the back.

has the PCM been reset recently? Long term fuel trims are 0...... which is suspicious. Also, is the O2 sensor BIS2 changing at all, or is it pegged at 1.0, and just stays there?

 

I’ll have a look by pulling the throttle body out by tomorrow morning. I don’t know if the PCM has been reset. And don’t have any idea of the long term fuel trim showing 0.0% and o2 bank 1 sensor 2 stays at 1. Not changing at all. Is it because of clogged cat and plenum leak?. I didn’t move the truck, but when reving the throttle for a while, the rpm drops 1000 every time. Thanks again for your help. ��

 

Thank you HeyYou, I’ll pull it the throttle body by morning and have a detailed look. The O2B1S2 stays at 1.00 not fluctuating. Don’t know if PCM been reset. Don’t know about the Long term fuel trim- stays at 0.0

 

Long term fuel trim being zero is what makes me think it has been reset recently. (battery disconnected, codes cleared, or something....)

If voltage is fixed at 1, either the sensor is bad, or there is a short between the sensor wiring, and the heater......

 

I did disconnect the battery after my drive to the gas station. And next day the check engine light went off and came back in a while with P0141. I’ll take off the 02 b1 sensor 2 and check for any damage. please advise any other required diagnosis.

 

I just found out that the heater relay for o2 front and rear is missing. Do you know why it has been removed ? I checked for any wire damages in o2 sensors, all seems good. I’m trying to narrow down the problem, please help me out. Thank you

 

No clue why someone would remove it...... Just get another one, and stick it in there. Clear the codes, and see what happens.