My 1994 1500 4x4 5.9 Automatic has a issue once it gets warm. When I start is cold it runs like a champ, it seems that once it gets warm, it runs like it's on 6or7 cyl[].
Parts I've replaced:
plugs/wires/cap/rotor/pickup coil/egr
It will get to a point where I can barely roll [:@]. I thought the gas tank was corroding and blocking something, but it appears to be a plastic tank.
max@mdg911.com

 

Does it lose power? Or does it run really rough?

Just a thought that stems from a problem I had with my truck recently. My truck would run perfect until the computer went into closed loop mode and started getting information from the O2 sensors. It would take about 15-20 mins to warm up (it's cold here) then it would sputter and run like crap. I changed the O2 sensor before the cat and the problem is completely gone. It didn't throw any codes at all.

Good luck with your problem

 

the truck has NO POWER I'm lucky to roll at 5 mph to get out of the roadway. Strange thing today... put a bottle of Justice Brothers FI cleaner in and 9 gallons of premium gas (while it was having the crappy run issue) it sat for about 5 minutes and has been running very smoothly.
My mechanic leaned more towards the fact that maybe my gas guage is bad (go figure). I am going up later to fill it with gas to see how many more gallons it will hold.... if it takes 26 gallons more I'll feel like an ***!

 

sending units are really bad in our trucks so dodnt feel too bad. I would think maybe your o2s could be bad as someone else said. have you had your plenu fixed yet?

 

Can the o2 sensors really make a truck run like crap? Mine runs rough and the oil pressure gage goes real low. Al;most stalls. The trouble codes I get from the check engine light are 37 21 & 32.

 

I have replaced O2 sensors that have made vehicles almost undriveable....stall....run VERY rough...I think one of your codes is an EGR code as well....they can cause problems like that too. What year is your truck? If your Plenum is bad it can wreck the O2 sensor before the cat...mine actually had a short in the wires right at the sensor but still didn't show a code.I don't think theO2 sensor has anything to do with how the truck runs at cold startup..it sends a signal after the vehicle is warmed up. I believe the PCM gets this info from the temp sensor then reads the O2. So if it fires up and runs good only to start freaking out after its warmed up a bit ....O2's could be a problem.

 

It is a 1994 Ram 1500. It runs good until it warms up.

 

well the temp & O2 sensors are both fairly cheap....I would put my money on the O2...but it could be the temp sensor giving a false reading.....you would have to test them individually I think it's in the manual ....I'm lazy so I would probably just replace the O2 first if its old because it would be a good thing to get done anyway. The O2 sensor before that cat is the one to look at. If that doesn't do it ....I would go with the temp sensor.....unless of course either of these have already been replaced in the recent past.

oh and I would check your plenum.

 

I would bet on some partially plugged fuel injectors,
perhaps where the interior of the fuel line has started to come apart
and plugged the little screens at the top of the fuel injectors.

When the engine is cold the air/fuel is made very rich
then after 147 degrees coolant temperature it tries to idle at 14.7