My truck has been driving me crazy!! Can anyone help a buddy out?

My truck has always, up 'till now, given me little to no trouble. But about six weeks ago, i swapped out my rear end for a spare I had 'cause mine was shot. (I found later, to my dismay, that this was a 3.21 and my old one was a 3.55...) At the same time, I installed new shocks. as I was trying to bleed my brakes, I blew a hole in my brake line. I fabbed a new one, and luckilly was able to remove the old one and install the new one without dropping the fuel tank. (I mention this, only because you may need to know for proper diagnosis...) After swapping over my old brakes, speed sensor, and tightening lines, I attempted to fire her up. However, the motor only turned over and over, and only fired after a prolonged period of cranking. Then, I had to keep revving the engine to keep it from stalling out. No "Check Engine Light" or anything! I used my Hypertech programmer to re-flash the pcm, which seemed to help. At times, she would run great, and at times, she would stall out anytime I came to a stop. (Continued)

 

But she always seemed to run worse when it was wet out. At times, my volt meter would drop, and several times dropped so low my "Check Gage" light came on. Then one night, she just cut off. Completely, while rolling! I popped the clutch, hoping to revive the motor, but no good. The radio was still playing, but the tach, speedo, and all my other gauges were dead. I made my was to the shoulder, and turned the key over. Nothing. No fuel pump, no click, no noise whatsoever. So I popped the hood, and tapped on the connector leading to the underhood fuse box, then tried again, and she fired right up and got me home. I have been seperating connectors, spraying them with electrical parts cleaner, packing them in dielectric grease, and reconnecting them. I tackled the distribution plug, the pcm plugs, and the two under the driver door leading to the back half of the truck. But tonight, she cut out again. Just like before, but I can't crank her but tapping plugs.

Whew!! Can anyone make any sense of this?? Thanks in advance...

 

the drop in the voltage gauge strikes me as one of the most important problems. there's a complicated interaction between the alternator and the pcm for voltage regulation. in addition, low voltage, for whatever reason, plays hell with the IAC idle control. the tap on the PDC box is important too.

i'd recommend removing the battery and the alternator and taking them to autozone or similar for an isolated bench/load test. if they're not any good, then it screws up everything else.

have you removed and cleaned battery cables ?
voltage check the battery when off ?
votage check the battery while engine running ?

and everything was fine until the rear end swap, right ? and then immediately everything was screwed....

 

HOLY CRAP, That's mine. Runs like a champ but lately it has started to have a mind of its own. At first I thought weather (Moisture), but since it happens randomly that "cause" was ruled out. I have been looking around and like dhvaughan if the battery and or cables are not in the best shape you can have all sorts of issues.

I know that both my cables need to be changed, but the prior owner did some odd wiring so I have to do other things too so maybe the wife will let me stick the nose of my ram into the garage this weekend where I have portable heaters :-)

 

Sounds like you may be shorting out a logic ground to your PCM. The sense lines to and from sensors to the PCM should not be grounded to the chassis. You did all this hardware swapping it is possible you may have crimped or frayed one of the wires. I had the same issues with my 97. The logic ground on my upstream sensor was shorting to my tranny pan causing my PCM to freak out. Any time I would stop the throttle would start sucking tons of air (can’t remember the name of the valve) and it would stall out. As long as I was on the gas it seemed fine but it ran like the timing was off which we all now the PCM adjusts this. I replaced the O2 sensor and never had the issue again.

Oh ya, that is a damn fine Dodge tom.

 

Yeah, I had a weird incident with my o2 sensor, though; quite a while ago, the rpms jumped to 3000 on it's own, and I threw a trouble light for a o2 sensor. But this wouldn't make it shut down altogether, would it?

 

yea i would def check all grounds around battery to start, i had problems with my IAC acting up not working all the time, put in a new one ran good for two months, then same problem, come to find out it was a bad ground coming off the battery, everything else work good and it was a intermitent problem, and for the record the stock battery terminals suck, one the neg one of mine the wires were loose and untill i changed it sometimes it would'nt start and i would have to get out and wiggle the wires.....

 

estech said that his o2 sensor was grounding itself and it made the pcm freak out, so yes it is a possibility.

you mentioned tapping the wire that goes to the PDC, is that wire smooth like a new wire or does it have bumps in it? if that thing is full of corrosion, or if it has corrosion where it contacts the PDC then you'll have issues.

a bad connection to the battery will cause issues. if you still have the band style terminals then cut them off and replace them with the lead style and put the felt pads under them. clean the battery posts also.

 

No, It was the massive plug with a bolt through it. I'm going to try to retrieve her today, so I'll start by checking all the grounds. And I have had the alt tested, but I pulled up at the shop and everything perked up! They said everything seemed to be working fine but the alt was having to put out more than they thought it should have to (around 50 amps, I think?)

 

Update: I started going through the grounds, and the main ground retaining nut had backed completely off! Three hours and $4.00 later, runs better than she had for three months!! Thanks to all!!