2000 Ram rough idling/ bad mpg / no fuel trim for 2nd sensor

[Townesy]

Hey everyone I've got a 2000 Dodge Ram with the 3.9 v6 and I've noticed a lot of rough idling for awhile, I get heavy vibrations while driving sporadically, plus vibrations when rpm increases while parked. I bought a scanner just too see what was going on. and I've got voltage meters for both oxygen sensors but only the fuel trim for the first sensor. Heres the graph
I've replaced the idle air control valve and don't have any exhaust leaks. I also have voltage until the connector to the second O2 sensor but done have a way of testing after.
any help would be greatly appreciated and where to go from here wether it may be the cat or do I need a new sensor

 

[Fast69Mopar]

Well, you are not going to have a Short Term Fuel Trim for the 1/2 oxygen sensor. You need to look for the 1/2 Long Term Fuel Trim.

Once you see what the LTFT is doing on the Downstream oxygen sensor it will aid in diagnostics. Your short term fuel trim is not terrible in the pic you posted. The PCM is pulling a little bit of fuel at idle bit not much.

3.9's aren't the smoothest running engine in the world because it is an odd-fire motor. It's rough from day one compared to the 5.2/5.9 because they are even-fire motors.

When was the last time you had the spark plugs out? Pull them and check their condition.

Check the plenum gasket as well. Pull the breather hose off of the air hat and feel how much vacuum is being pulled against your thumb. If the gasket is pushed out in the plenum you will feel a heavy vacuum against your thumb.

 

[Townesy]

ill have to run the long term trims tomorrow, I replaced the spark plugs about 2 months ago and the old ones didn't seem to be too bad, spark plug two had some blackening but thats its. plenum plate looks pretty good as far I can tell. did the vacuum check last week and there was no suction










thank you for the help

 

[Townesy]

I could only load the long term fuel trim for bank 1

but I checked in another section called mode 6 and saw this:


but went and checked my smog test section and says my o2 sensors are fine as well as the catalytic converter is fine as well. any thoughts on what could potentially be my problem?

 

[SportRam00]

That LTFT looks good. From what I've read fuel trims (short term and long term) should be close to zero and not be higher than 10% each way at idle.

Have you though about routing your plug wires according to TSB 18-48-98? http://dodgeram.info/tsb/1998/18-48-98/18-48-98-v8.htm

That helped clean my idle up slightly. Also check the condition of your wires and cap and rotor. Make sure they aren't worn or cracked.

I use a widely used scanner app for my truck and my O2 sensor also fails the 11:01 test. The truck runs fine though.

 

[Townesy]

awesome ill check all my wires and caps and try rerouting the plug wires. Thank you

 

[SportRam00]

Also, have you replaced your O2 sensors recently? If so, what brand did you use? These trucks are apparently sensitive to sensor brands. I'm running NTK/Denso sensors in mine. I was chasing the 11:01 component failure as well. Even after new sensors, I still get that failure. There have been issues with people running Bosch O2 sensors.

 

[Townesy]

I don't think they have been changed recently but ill look and see if there Bosch, if they are ill look into some new ones