I have a 2001 ram 1500, 5.9L 2wd. About two months ago I noticed that when I was idling, the engine would occasionally have a little shimmy to it. I'm talking one to two little jumps, pretty infrequently. Now, at idle it runs fairly rough. The rpm's drop each time it jumps, but its hardly noticeable on the gauge. Also, when accelerating from about 40 mph, the engine will lurch, and continue to do so until I hit about 50-55 mph. Just recently this started occurring when I start from a stop as well. Today I pulled the spark plugs, and all of them were clean. I think it's an ignition problem, but haven't had a significant drop in gas mileage. Has anyone else had this problem, or know that the cause is?

 

"the engine will lurch??.......... sound like a tps, bad plenum, iac?? come on guys what do you guy think?

 

Have you done a full tune up in a while? You might check the coil as well.

I have a slight stumble at idle I have been trying to track down as well. I have replaced all of those parts and still can't find it. I'm thinking I have a gremlin in there somewhere.

 

I haven't had a full tune up in a while. The fact that the engine idles rough whether its in park, neutral, or drive excludes the possibility that this is a tranny problem, right?

I think I'm going to try and clean the throttle body (that suggestion has come up several times from different people), the problem is just finding the time, and figuring out how to do it. Hopefully that will help, but if anyone has any other suggestions, please keep 'em coming.

 

Seen this problem with a TPS before on my aunts Dakota. Found it by lightly tapping the body of the TPS while running, with a screw driver. It would give little lurches. These damn distributed motors really like a clean distributer though. So check what you can.

 

So I removed and cleaned the throttle body today, re-installed it, and took it on a test run. The problem is still there. The idle is a little less rough, but still jumpy. The lurching seems to be more serious, with bigger and longer jolts. A correction from my previous post, the RPM's increase (not decrease) when it lurches. Being only slightly mechanically inclined, was cleaning the throttle body with carb cleaner and paper towels what was suggested? What's this TPS deal? Is that one of the actual sensors on the throttle body? I also had the engine backfire twice on me today while giving it pretty good gas, accelerating past the lurching speed (~65mph).
I'm thinking maybe I didn't clean the right things on the throttle body, so if anyone has any info on what I should have cleaned, please let me know.
Also, any thoughts on if the culprit could be bad fuel injectors or dirty fuel filter?

 

I have a '99 Dodge Ram 4x4 5.9L, and am having the same problems. I don't drive the truck very often, but have noticed that problem three times since I bought it last November.

The first time I just happened to be pulling into a parking spot, and it was jerking and lurching and the RPM's were fluctuating... I turned it off and turned it back on, and the problem was gone.

The next time it started at a stop light about two months later, and turning it off and on did not help this time. It jerked and lurched, backfired all the way across town. I then disconnected the negative battery cable and reconnected it, and the problem disappeared.

Then last night it occured again while driving down the freeway with the cruise set at 65, the engine started jerking again, but that lasted about 20 seconds, then the tranny kicked down and the problem disappeared.

I did have a CEL light come on earlier during the day yesterday (before the problem occured), and had it checked out today. Turns out to be a P0420 code (Catalyst Efficiency Below Threshold). That was the only code in the system- and the tech said that shouldn't be the cause for the jerking and rough idle.

I've also noticed that, like you, my truck tends to have a bit of shimmy at idle- and has a rough idle when first started. If I punch the throttle up, and let it drop, it will then start chugging like it wants to die... but then after a few seconds it will go back to the shimmy idle. If I have the hood up during idle, it can be seen and felt to wobble.

Hopefully someone has some answers here, because it's desperately needed. I just replaced the plugs, plug wires, distributor and rotor- yet the problem persists. Surely a bad catalytic converter wouldn't cause this. I just wonder if there is a possible computer problem- especially since that time I disconnected the negative battery and reconnected- and the problem disappeared.

Any thoughts?

 

I found this online regarding symptoms of a bad catalytic converter;

"So if your vehicle begins to run rough, or the CHECK ENGINE light appears, have the vehicle checked out immediately by a professional technician. Further symptoms of a faulty or failing catalytic converter may include, failing an emissions test, increased engine temperature, bucking and engine hesitation."

I also forgot to mention, when I changed the spark plugs, they were NASTY. It was obvious the previous owner had never changed them because they were rusted to the engine. The gap is supposed to be .040 and they were all over .050! I noticed that they say one way to ruin a cat converter is with bad plugs.

I'm curious to see if anyone has any other ideas about what our jerking/lurching and rough idling might be.

 

check your fuel pump.. i had the identical issues with my 98 w/318.. changed the fuel pump and seems to be gone. idles and runs good.

 

I noticed today that my plenum gasket is blown. I guess that's why I've been using oil. I plugged the PCV opening and checked for vacuum on the opposite valve cover breather hose, and there was solid vacuum. I peered down the throttle body and saw pooled oil. :-(

I then took a rubber mallet to the cat converter to see if it rattled, and it doesn't. In fact, it actually sounds hollow. Does a cat have to rattle to be bad?
The only thing I have to go on is the P0420 code and the occasional engine problems. Previously I was getting an oxygen sensor code, but I haven't seen that lately.

I do know that the rear- after cat- oxygen sensor was replaced last November... but a month later I got the sensor code again. So would a failed oxygen sensor on the cat cause a P0420 code. Or could the cat converter still be bad?

-Brad