A few weeks ago, I had the dealer perform massive surgery on my 5.9 2500, and ended up with a new ignition system (new distributor, cap, rotor, wires & plugs) among other things. The truck ran great most of the time for the first week or so, then I started noticing that it was a little stumbly when I first tipped into the throttle from a stop, but it pulled cleanly after that and after it was warmed up.

Today, it got a lot worse. At first, it was just a very rough idle that wouldn't clear, but again, after some driving it went away. Then it started surging on the highway at about 2000 RPM, not a lot, but about 200 RPM on the tach.

Then, as I was tooling around town, it completely lost all power and started quietly backfiring. Not loud explosions, but definitely coughing through the exhaust. The pedal went limp and revving it in neutral didn't help. It was like the distributor was off a few teeth.

I shut it off and turned it on a few times, and it seemed to get better. I drove it home on the highway without incident and now it's running fine. I suspect it'll run like crap again tomorrow morning, however. The Check Engine light has not come on, even during the backfiring.

Of course, my first move is to take it back to the dealer who did all the work--I have an appointment Tuesday. But does anyone have any suggestions as to what it may be so I can talk with some intelligence with the dealer? Maybe it's the PCM? Perhaps a bad fuel filter/pump/injector? Since it's backfiring, my best guess is that it must be ignition--a bad injector wouldn't cause backfires or a limp pedal.

Also, I installed a new TPS when I went through the spark plug fiasco--could I have installed it incorrectly? Maybe the pot is oriented incorrectly on the throttle shaft?

I'm really starting to regret purchasing this truck--it's the only truck I ever wanted but it's turning into a very expensive headache.

Thanks and sorry so long.

 

Hi Matt, I'm taking a guess on this one. Leak in the intake manifold. Requires a new gasket. Happen to me a couple of years ago. I have a 98-360 quad cab 2wd.
It happens to some of the 360's not all.
Lets see if some of the mopar techs will help us out here.

Cheers
KayakMan

 

Matt how ya doing and good luck on fixing your problem!

Though an intake gasket would cause these problems, it would be very consistent and only get worse over time. It would be consistently bad all the time.

With all you had done I noticed in your post that a coil was not replace. Coils that fail dont necessarily fail all at once. Some fail as the truck warms, some crack and get moisture in them overnight and so the truck runs like poopy till the moisture is heated off.

It sure sounds like a coil, I would check it from a buddys truck or purchase one as they are not expensive!!!

Also, that 200 rpm surge is just your truck kicking out of torque converter lock-up (overdrive) from running like poopy. Fix the miss and that problem goes away as well...Happy hunting and let me know what you find--

red tonka

 

hows your cat? have you had it looked at? these cats are notorious for falling in on them selves... and could cause your symtoms. IIRC your exhaust temp should be hotter on the exit side of the cat then the intake side... if you have or have access to a temp gun,, id check it.. these cats like to plug... greatly raising your manifold temps to the point where the heads like to crack... IIRC again..there might be a recall on the cats.. not sure..either way its not expensive to get a new cat installed depending on where ya go..

the cat idea might be a long shot but something that still should be looked at.. on the TPS deal.. im pretty sure they only go in one way.. the connected on the bottome side.. as i just had mine off a few days ago ..

coil idea might be right... they are cheep and easy to relpace as well..

just to check..make sure the airhat is installed right.. one time cleaning my filter i didnt put the airhat back on tightley and it ran like garbage..sucking air in at the mouth of the TB

btw IIRC means if i remember correctly...incase you didnt know


hope this helps..good luck

 

Thanks for the replies, guys. I'm going to go get a new coil this morning and try that first. It can't hurt, right?

I also asked the dealer about the cat, but they said I didn't need it. Perhaps I'll get a second opinion on that. And I'm pretty sure that it's ignition related simply because it's intermittent. If it were the fuel system, PCM or a manifold leak, it would be all the time, and probably wouldn't cause backfires.

I was also thinking that perhaps a plug wire got caught on an exhaust manifold or something and melted through. It may be grounding out on the manifold under certain situations, so I'll double check that ,too. Oddly enough, this thought came to me in a dream last night. Hmmmm...

Thanks again and I'll keep you updated.

 

Hey guys, I hate to bring this back up but yesterday the same problems returned. It was again idling like crap with a bad miss about 5 minutes after I started it and drove to my other house 5 blocks away. I opened the hood and revved it manually and it backfired through the air cleaner a few times when I revved it. It's got an occasional stumble and idles like crap when it's cold. It also has trouble maintaining the usual 650-675 RPM idle speed, usually dropping below 500 and struggling. The limp pedal has happened a few times, too. When I first tip into the throttle from a stop, I usually expect it to stumble for a second or two, then get under way.

I disconnected the battery for an hour or so, then reconnected it and it seems fine for the moment. So WTF? Can the computer be getting a bad signal from somewhere and changing the block learn or something? I still have no Check Engine light or codes. Or disconnecting the battery and the disappearance of the problem could just be coincidence.

My next guess is perhaps the O2 sensors, though I know they don't really operate during cold start and idle. The cat may also be suspect, but I don't know why unplugging the ECM would affect it and it would probably be a constant problem, not intermittent. Then I thought about a vacuum leak, but couldn't find one with some rudimentary searching around the engine compartment. And the leaky intake would probably cause problems all the time, again, not intermittently. Is there an intake air temperature sensor or a manifold absolute pressure or baro sensor on these engines?

Could it be the transmission? I know I'm on borrowed time with it, though it works perfectly. Could the torque converter be binding or something to pull the idle down? A bad VSS signal or something?

Here's what's new:

Distributor
Cap, rotor, wires, plugs
TPS
Computer does NOT have the death flash as far as I can tell
Intake seems dry

Any other thoughts? I'm really starting to distrust this truck for doing any actual work and driving more than a few miles from home. The sucker only has 67K on it--it shouldn't be running like this. I love the truck, but remind me to never buy another Dodge...

 

REPLACE THE COIL----it's cheap and I can almost bet that it has a crack in it and when it fails it loses the ignition to the distributor--------------------------------

REPLACE THE COIL---I had the same exact thing happen on my 95 so I am speaking from experience and I see you still haven't replaced that and I recommended that a while ago----guess I am offended---LOL

Let me know what you find


Also for your informtion---the coil when it fails will not throw a accurate code,,,,,,,things like the o2 sensors, crank sensor, timing, knock sensors, all sorts of things will light up on diagnostics when a coil fails or starts to...

And the coil is usually real intermittent and the symptoms vary from almost nothing to feeling like the truck is going to just fall apart--TRUST ME

 

Also---it might not throw any codes!!!! Just an FYI for when a coil fails!

 

If unplugging the ECM changed it, then it's PROBABLY a sensor going down somewhere. When you reset the ECM, the truck runs at factory "settings" for a while before it starts to "learn" via input from various sensors.

 

Rom --- I thought of that too....but there are no codes being thrown......

Bet you a friendly beer sometime in this life that its his coil????

What do ya say???LOL