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Ask Dodgerench Your Own Question
Dodgerench, ASE Certified Technician
Category: Dodge
Satisfied Customers: 3404
Experience:  30+ years Dodge/Chrysler exp., ASE Master with L1 certification. Driveability/ combustion specialist
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I have a 1996 dodge b2500 van with a 3.9 engine the problem

Customer Question

I have a 1996 dodge b2500 van with a 3.9 engine the problem is it will sometimes backfire and stall while driving or backfire and keep running some times it will stall when at a lite engune just cuts out.then sometimes hard to start and sometimes starts rite back up seems to do it more when engine ishas been running a bit sometimes it seems to be running fine on the highway then all of a sudden it trys to stall and backfire .. I have replaced coil . dist cap. spark plugs and cables rotor button. ecm. map sensor. idle air control motor 6 months ago i replaced both oxigine sensors .egr solenoid
Submitted: 7 years ago.
Category: Dodge
Expert:  Dodgerench replied 7 years ago.
HiCustomer welcome to Just Answer!.

Have you noticed whether this happens more often (or exclusively) when fuel tank levels are at or below 1/2?

Customer: replied 7 years ago.
it can do it full or half full or near empty
Expert:  Dodgerench replied 7 years ago.

I'd like you to check to see if we have codes stored if the van is nearby. An actual scan is preferred, something you could have done at your local Autozone if convenient but a second option is the "flash method" of code extraction that's built into your vehicle electronics. It's not as accurate or specific as an actual scan, but works in a pinch.

This is how it works...
Roll the key from off to on three times, leaving the key ON.

Watch the CHECK ENGINE lamp as it does a longer than normal bulb check (close to 5 seconds) and then goes dark.

When the CE light comes back, it will be flashing, so be ready to keep count.

The pauses between flashes tell you what to do, much like Morse Code. Short pauses mean you should continue counting... this digit isn't done yet.

Longer pauses mean the digit is completed and you're moving on to the next one.

All trouble codes are composed of two digits, like 12 or 55, so you will always have an even number of digits once the flash code process is over.

Repeating the process 2-3 times is highly recommended if you're not a flash code veteran... codes such as 12 often become... "3" if the pauses aren't recognized.

Last, it sounds as if the van doesn't always die immediately on you... is that right?
It gets a little weak, maybe backfires as you go deeper into the throttle and then dies out?
Or is it a sharp ON-OFF type of feeling? As if a switch was turned?

Talk shortly,

Customer: replied 7 years ago.
when i stop at a lite it is a sharp on-off but when i am driving it is slow stalling
Expert:  Dodgerench replied 7 years ago.
That's just the way it appeared in your description. Thanks!
Let me know what you find for codes. Is there a chance of a direct scan?

Customer: replied 7 years ago.
i have had advanced auto check the codes all they get is cylider backfires I tried the codes but may not be doin it rute but i got 3-4-3-2-4-2-4-5-5
Expert:  Dodgerench replied 7 years ago.
The first number (3) is always a tricky one and is probably a code 12 (battery recently disconnected or PCM memory lost).

The next one (43) can have multiple meanings including misfire or ignition coil control circuit codes.

Code 24 is a throttle position sensor (TPS) issue, but also has multiple meanings with the flash code method. It's also quite possible that the code 24 was set accidentally while you worked in the area... hard to say.

Finally, code 55 means end-of-test... you will always get that one.

The code 24 won't cause steady speed or idle stalling, so we can disregard that for now.
Code 43 is another matter, but because of the vague nature of flash codes in this year, we're left with more questions. I'd explore the possibility of a loose terminal at the ignition coil at this point, something that most certainly happens on these units. If you can reach the coil connector with the engine running, wiggle it lightly while watching for a reaction. This places you very close to a dangerous area, so you might consider using a tool of some sort to reach in there... not your arm. I prefer to come in from the inside of the vehicle where you have good access to the coil without the rotating blades of death.

A loose coil terminal in the connector can cause the type of stalling you've experienced... either sharp and DONE or a prolonged stumble/ backfire situation. Check it out and let me know if we need to keep looking.

Customer: replied 7 years ago.
im back i checked the wires to the coil it seems to react with temperature the coil will lose 12 volts dc and not start or die quickly when running when engine is cool i may have to ground the coil to get spark and hook the coil wire back on to start it
Customer: replied 7 years ago.
also i did change one of the coolant temp sensors it is the single pin one that reacts the temp gauge in the cab but i have a two pin one also could that be bad and cause the problem and were is that one
Expert:  Dodgerench replied 7 years ago.
The second ECT sensor is right in the same area ...behind the alternator-A/C compressor. If you've already got one it probably wouldn't hurt to put it in. You'll need a 1/2" deep socket with no steps inside the socket area, like a Craftsman socket does. I like to use a 1/4"-drive setup for this due to the tight quarters.

I'm not sure if you're aware of it, but the 12v feed to the coil is cut off on purpose once the engine dies. It's powered by the ASD relay, which is turned off once engine rotation is lost... so it's gonna lose its power if the engine dies. It's a matter of whether it happens first to kill the engine that's important.

Speaking of coil wires, check yours to make sure it hasn't come into contact with the exhaust manifold which can burn a hole into it, allowing spark to short to ground. It happens.

Customer: replied 7 years ago.

it is loosing the 12 volts when i turn the ignition on sometimes i am reading it when i am cranking the engine.i also traced the wires back to the ecm and spliced a new wire in

Expert:  Dodgerench replied 7 years ago.
This is the same 12v feed that powers the injectors by the way. You might check to see if they lose power at the same time, as there may be a splice issue.

I'm wondering if you might be losing your cam or crank signal, listerman. If jumpering 12v to the coil has no effect on keeping the engine running, you may just be losing one of the critical rotation sensor signals which allows the engine to buck and stall. It's something that I would normally expect to see a code set for, but brief moments of signal loss are often missed by vehicle self-diagnostics.

While you're in the area, wiggle-test the pigtails that come off the cam and crank sensors and check for wiring rubs in the left-rear upper corner of the engine where all these pigtails attach to the main harness. This is a prime harness shorting area with the upturned valve cover edges and protruding bolt heads. Intermittent short to ground of these sensor pigtails can certainly cause problems like you've seen and leave no trace.

Customer: replied 7 years ago.
still have a problems i rechecked the codes and i got 12 -21-55 and it really seems to happen when the engine is hot i still cannot find the two wire temperature sensor and can that shut the engine down
Expert:  Dodgerench replied 7 years ago.
Code 21? That's an oxygen sensor code, which might explain some of your trouble with loss of power and backfire, but it won't cause a stall while driving. Maybe at idle if it gets bad enough, but certainly not with your foot in the throttle.

Maybe I was wrong about the ECT location in 96. I'll recheck and get back to you...

Expert:  Dodgerench replied 7 years ago.
It shows to be where I expected it. See if this diagram fits what you have...


Customer: replied 7 years ago.
im back thanks i found the temp sensor and replaced it but still having problems with it dying i went ahead and changed the crankshaft sensor and it is still dying i hooked all sensor back up and now my code is 12-11-55
Expert:  Dodgerench replied 7 years ago.
Hey! It finally spit something out that we can use!

Code 11 is an ignition reference code... bad crank sensor. You're losing your crankshaft position signal and as luck would have it, you have the one vehicle in our entire lineup that it's easy to replace.

You'll find the crank sensor mounted on the right-top of the transmission bellhousing, at about the 2:00 position when viewed from inside the van. Examine the wiring from the sensor pigtail to the engine harness where it connects to be sure there are no pinches or rubs that could cause shorting of the wiring and then replace it.

And THAT should do it!
Persistence pays off sometimes, huh?