First, I want to say that I am new here. I do not own a dodge truck (I am a shelby dodge guy though), but I am working on one now and need some help. I am an ASE certified (as if that means anything) technician, and I teach auto technology for a living. SO, I am not inexperienced at this. This is the first problem I have come across in a really long time that I am ready to throw in the towel on. I am coming to you guys for help......so please help!

OK here it is: Its a 95 Ram 1500, 4x4, 5.2, auto. The truck runs rough and stalls out at idle. It runs good as long as there is a load on the motor. This is an intermittent thing....and theres no rhyme or reason to when it happens, but happens mostly when its cold. Sometimes it runs PERFECT. When it does run rough, it is running PIG rich.....over 1 volt on the O2. The MAP is showing 2.5 volts at idle, which is very high. Something is causing an erroneous vacuum reading or something....... Ive checked many, many things. Fuel pressure is a steady 41 PSI. Ive checked for vacuum leaks inside the crankcase thinking it might be the infamous intake gaskets....no dice. Ive replace the MAP, TPS, Idle motor and coolant temp sensor. Ive double checked grounds to the PCM and important voltages (like MAP and O2) at the PCM. Wiring doesnt appear to be a problem. I know that these PCM's rarely go bad, but I swapped in another PCM from another truck. No change. At my wits end, I leak tested the EGR and it was leaking a bit, so I made a block off plate and installed it. No change. IVe even done all the tune up stuff...... Im going nuts here and I am running out of ideas Ive got a scanner, DVOM, and all the test equipment (except the chrysler DRB), so I do not lack resources. Does anyone have any ideas?

If you can give me a good tip and lead me to the fix, a thank you note and check will be in the mail to you ASAP!

-Sean

 

I dont know how this would help, but have you checked for any hot grounds???

 

Just a WAG here but is the battery fully charged?

Even if it has enough power to start but is low it could cause it to run weird.

Try that and if it works PM me for the mailing address for the check.

 

You mean a short to ground? I havent check for that specifically.........but I will.

 

Yea, battery is charged up.

 

yup, everyone calls it something different

 

Good luck be sure to tell us what the diagnosis is.

 

replace the battery or check the alternator.

 

first off... your fuel pressure sounds like it's outa spec... from my understanding, the non-return type fuel rails need the fuel pressure at 49 psi +/- 5psi, you mention that it runs right most of the time and when it does run rough, it's rich... could you have a vacuum leak that is intermittant? As in maybe the brake booster is leaky, (that's the case on my truck), and could your throttle body need a good cleaning, as in IAC and the little air ports might be plugged. Also there is a problem with the vacuum controller going to the enviromental controller inside the cab, there is a vacuum line and a check valve that will go bad causing the flaps to go to defrost under low vacuum conditions (probably doesnt apply in this case but thought I'd throw that at you anyway). also the CAD unit for the 4x4 also has vacuum line to it and it could be leaky.

Another spot is the EVAP canister, they get busted, lines get old, cracked and can leak intermittantly... check those out

please post back what you find in any of this...

 

I spent another few hours on it yesterday........According to alldata, the fuel pressure spec is 40-45 PSI. I dont think low fuel pressure would cause the rich condition I have. I have checked for vacuum leaks in multiple ways. I have a leakmaster system, which pumps smoke into the manifold and the smoke escapes where a vacuum leak is present. I also pulled the vacuum lines off the intake manifold and plugged them one by one and ran the truck without change. So, if theres a leak, I cant find it. I have cleaned the T.B. unit with intake cleaner with the truck running. My next step is to pull it off and clean it. I also spent a long time checking and cleaning the ground wires on the truck. No change.[:@] I got another tip from my father....check the battery temp sensor ground wire as it is known to corrode and cause the sensor ground to be faulty.

The grounds are weird on this thing. I check the grounds at the PCM with the connector disconnected and I get .4 ohms, which is good. Now, if I plug it in and turn the key on, the grounds go to 60 ohms. Now, I think this is due to the fact that I am introducing the PCM into the circuit and now I am seeing the resistance through the PCM......but I am not sure. 60 ohms is a lot. I want to set this thing on fire[:'(]