tha o2 that is

 

clogged cat

 

Your problem (the original first one you wrote about) about it running bad, mine is similar. When I bought this truck the guy who had it Im thinking didnt have any money to fix it, there was open vacuum lines, the EGR was burned open, etc. The computer wasnt working at all, yet this truck would start and run.
After buying a rebuilt computer (ECM) and replacing most of the solenoids and emissions stuff and sensors, I now have this problem. Most of the time it runs great. But once in a while, while idling,it has a condition similar to when the float got stuck in the old carburetors, it acted like it was flooded and had no power. I had to keep hitting the gas pedal to pull it out of that state.. Another thing its does, after driving it on the highway for 30 minutes, it seems to lose top end power.
I have been doing alot of reading on this subject. The throttle plate is famous for getting carbon buildup, so I used carb cleaner and got it squeaky clean. Still did it. I also got a computer code that the oxy sensor says the fuel mixture is too rich, and I read that could be due to a weak or faulty electrical system. So, I have ordered a MSD supercoil. I will also be getting a rebuilt fuel pump, and clean out the tank while Im at it. I HOPE this will solve the problems. Ill keep ya posted....

 

Don't bother with the rebuilt pump. You will be replacing it again with a year.

For the running rich, check you engine coolant temp sensor. (its the two wire sensor on the drivers side of the thermostat housing.)

Have you check your plenum yet? Sounds like you may have a cat that is getting clogged.

Supercoil isn't going to help you either. Stock coil is more than adequate to the task for most bolt-ons.

 

well as far as the temp sensor-thats brand new- just been replaced. I appreciate the advice on the coil and pump, but what is the plenum? Is that the evaporation fuel canistor? If so, that could be the problem as I can smell gas in its area. I was wondering if it was clogged. So should I replace the unit or is there a way to fix this? Thanks for your advice

 

The plenum is the intake manifold. there is a plate on the bottom of it that likes to blow the gasket. Read this https://dodgeforum.com/forum/2nd-gen...um-thread.html

 

Hey

I recently purchased a 1999 1500 4.2 Laramie Automatic and have the same problem (as your original post). Did you ever resolve the issue? Does anyone have any other advice to try?

Thanks!

All the best,

Ben

 

The original post is 2 years old, so I doubt you'll get an answer. But,pretty much all you need to know has been provided.

 

Hey check your cap and rotor, and wires because they were so correded on mine that it was firing between cylinders and caused an issue that was immediately fixed after re-replacing these parts.. Do the whole kit, not just cap and rotor, do the wires as well!

 

I agree with RAWR. I had already ordered a supercoil before I posted last. I got it, installed it, and put a new cap, rotor and wires on. It still had a slight miss, but man what a difference! It had acceleration like never before. I checked the plugs and they were carbon fouled, and I read that a weak ignition system can cause that. I cleaned all plugs and now it runs smooth as glass