I'm having some problems with my 2001 3.9L 2wd, auto. I have 132k on the clock and im starting to have a problem. It will bog down and even pop a couple times when driving at slower speeds/rpm's. Its like it cant breathe or get fuel. My air filter is fine and thought it may be a cat. like it was clogged, but I haven't thrown a code, so I thought maybe it was my fuel filter or possible an injector? I haven't had a chance to look at it too much as im at college in Vermont, but this weekend I will be going home to CT to look at it. I put some fuel system cleaner in it for the trip home hoping it will help a little. It doesn't do it really on the high way or higher rpms, but driving through town it will bog down and not want to go until I really give it to her and get on it in which it may still take a second to really get going. I will even pop sometimes or idle real low. Just trying to list all the symptoms here.

Any help I would appreciate a ton!
Thanks.

 

could be the cat it won't always throw a code i think there is some time of back pressure test or something a garage can do on it. i may be wrong but i think the fuel filter is in the tank if they are you better hope its not that lol cuz that would be a bitch to get at and change. whats your gas mileage like?

 

yeah, fuel filter is part of the pump assembly, cant replace the filter, pump goes with it too... enjoy

 

if it's only at slower speeds id probably rule out the fuel pump. It pumps less at lower speeds and more at higher...

 

First thing to check is the trouble codes from the PCM. You can turn the ignition on and off 3 times then on and leave it on and any stored codes will display in the odometer. If there are any codes they will point you in the right direction to fix it. Even if the MPG has not gone down I would suspect the upstream O2 sensors, especially at 132K. An O2 sensor can be "lazy" and not store a code but still cause a lot of problems. At 132K I would say replacing the O2's would be good preventative maintenance. The downstream O2's don't usually have problems. If you need new O2's use NGK or the OEM parts from the Dodge dealer. The Bosch O2's sold at most parts stores do not work well in the 3.9. NGK can be purchased online too I think.

The poor idle can be caused by a faulty O2 causing problems with the Idle Air Control sensor. This would be a really good time to remove the Throttle Body and clean it very well, clean the IAC air passage with a toothpick and reinstall the TB with a new gasket. Lubricate all the TB linkage pivot points with spray silicone. It is a good idea to replace the IAC sensor if it's questionable. Make sure the Throttle Position Sensor is working properly too. With the key in the run position and the engine off the center lead is supposed to have .3 volts with the throttle plates closed and and a maximum of .75 at wide open throttle. Check with volt meter set to milliamps. The IAC and TPS don't cost much if you need or just want new ones.

After checking/replacing parts be sure to disconnect the negative battery cable and hold the ignition key in the start position for 30 seconds to reset the PCM.

Jimmy

 

Thanks, Im going to look into some of those things and I will get back to you guys. Thanks again.

 

last i checked it was .3 volts at low idle and 4.5 volts at WOT... with the DMM set in the VDC scale. and the .75 volts is the max voltage at low idle.