Befuddled by my 1996 Dodge Dakota


I have a real thinker problem here. I have a 1996 Dodge Dakota sport. 3.9L Magnum engine, 5 speed, with 128,000mi. When I first bought the truck a year ago it ran great and got about 25mpg. Since then it has been steady downhill. Now it gets maybe 13mpg at best and its idle is very rough when cold, and not exatly great when warm. When cold it pops a bit and the tach jumps erratically while idling and bogs when driving, when warm the idle seems to pulse up and down and it feels like I am not getting the power I used to till it hit at least 3000RPM. Also under load the engine makes this weird noise, almost the sound that injectors make but a bit loud to be the injectors.

Here is what I have done, changed the plugs out, pulled injectors and cleaned them, pulled throttle body and cleaned it, replaced the distributer cap and rotor, replaced coil and plug wires, replaced TPS, replaced IAC sensor, replaced all the vacuum lines and made sure there is no leak, and replaced the air filter, replaced all of exhaust system. Nothing seems to have affect this. And the check engine light is not on, so there are no trouble codes. Anyone have any other ideas as to what might be causing this as I am befuddled.




Does this version have a timing chain or a belt?
These sound like symptoms of out of whack valve timing. You can check this with a vacuum check. Refer to the manual for details.

  • mountainbike


Yes it has a timing chain. The chain rattles a little every now and then, but these engines are notorious for having a timing chain rattle. I have spoken to a bunch of people with the same truck and all have had their timing chains last well into the 200,000mi mark. Just to be sure I think you are right and I need to do a vacuum test. Maybe mine is an oddball



You might want to post your question or do a search on

There’s a lot of knowledgable folks on this site. They were helpful when I had my 95 Dakota.

Ed B.


Running as bad as it is & NO check engine light?

Does the check engine light come on with the other idiot lights when you turn the key?


Yes the check engine light comes on when I initially start, but like all the other idiot lights turns off again


Interesting, i’d think you should be geting a check engine light & -at least- a fuel system too rich code to match your OUCH 13 MPG.

Go figure.

I like mountainbikes idea of putting a vacuum gauge on it. That might give you a clue on this.


Put a timing light on it. You can watch how much the timing plays around. You could, also, put a wrench on the crankshaft bolt, and determine how much play is on the timing chain.


Just read thru your first post again & dont see any mention of checking fuel pressure.

On my Ford’s & yours is prob the same theres a vacuum hose connected to the fuel pressure regulator.

If the diaphragm in the FPR ruptures raw gas goes into the intake manifold.

Run it a few seconds & pull the vac hose off.

Is it wet with fuel?


Good idea! I do not have a Vacuum Gage and my timing light bulb is very weak, but I will try tomorrow with a wrench on the crankshaft bolt


Cannot say I have seen a FPR in the fuel system. I climbed under and followed the lines from the tank to the injectors without seeing one. On a side note, I used a flashlight to look down the throttle-body into the intake and can see the bottom of the intake is wet (with the engine off of course). With either fuel, oil or water I do not know. Ever heard of that?


The PCM pulses a ground to the injector to fire it, but only when the engine is cranking or running.

If it’s dribbling fuel in with the key on/engine off then the injector is stuck open.

Looks like you might have found your problem.