I have a 94 dakota 3,9 and yesterday when I started it up it was sputtering and popping thru the carb & exhaust. I started to drive it and when going up a hill it could barely make it.
I let it warm up for a while & proceeded to my destination that was 25 miles away.
After warming up it ran pretty good and quit popping but still had some hesitation when accelerating.
The return trip home was the same except I didn't have to warm it up because it only sat for a few hours.
I started it up today and it is doing the same as yesterday.

Any suggestions on what might be the problem would be appreciated.

 

Well if it's POOPING through the CARB, you have 2 problems lol. Sorry couldn't help myself there. Your '94 is Multi-Port Fuel Injected BTW. Have you tried to pull any codes off of it?

It could be a lot of different things causing a backfire, has any work been done to the engine recently? If not then I would start with checking the ignition system. Make sure the distributor hold down has not come loose and therefore messing up the timing. Check the spark plugs, wires, cap, rotor, and coil. Also check the wiring under the hood, sometimes small animals can get in there and chew stuff up.

Could be bad fuel maybe.

I think when the plenum gasket blows out on these engines it can cause the engine to run very poorly as well and is a very common problem.

 

No recent work done on the engine.
Distributor seems tight .
I Haven't changed the wires cap or rotor.
How can I check the coil?
Fuel is ok.
Under hood wiring looks good.
How can I tell if it's the plenum gasket?
By plenum do you mean the intake manifold?

It runs better after it's warms up.

 

Some parts stores can test coils (not always accurate though), but if you can't have it tested you just have to buy a new one... they aren't too expensive. Go the cheap route first before throwing parts at it though.

By plenum gasket I mean the pan gasket at the bottom of the intake manifold that seperates the lifter valley from the manifold, they are notorious for blowing out. Usually a tell tale sign that it is blown is a puddle of oil in the bottom of your intake. To check, get a flashlight and pull off your throttle body and see if there's a pool of oil at the bottom.

Don't forget to pull some of the spark plugs out to check and see if they are fouled or not.

 

I have a feeling that it's not an electrical problem because it will idle smooth so that makes me think it's not a plug fouled or wires or coil, but I'm no expert so I could be wrong.

I would think that if it was electrical it would run bad all the time instead it runs better after it warms up making think it could be a vacuum problem.

 

This really could be a lot of different things. You need to check the codes https://dodgeforum.com/forum/1st-gen...-96-codes.html . Sometimes codes will be stored and not illuminate the CEL, hopefully the computer has noticed something that can point you in the right direction. If not then start tracing vacuum lines if it's acting like it has a leak. Check the FAQ for any info.

One last question, does it still misfire or sputter when you're in neutral/park and rev it or is it only when under a load (in gear)?

 

i checked for codes and there are none, just the 12 & 55.

Sometimes I can get it to pop thru the carb in neutral if I push the pedal to the floor real quick.

Does this sound like a vacuum problem to you?

 

Not really, a vacuum leak can cause rough idle and hesitation, but you said it idles somewhat smooth. Sometimes you can hear a hiss with the hood up if there is a significant vacuum leak. Could also be an exhaust issue like the cat being clogged, but then IDK why it runs better when it gets warm. Maybe it's a fuel issue and once it gets into closed loop it runs better. Hopefully someone else that has had a similar issue will post on here soon.

 

Could you possibly have a bad coolant temp sensor that is sending a bad signal during open loop operation, and once you hit closed loop temperatures, the O2 sensor is able to compensate and correct your fuel delivery?

 

+1 to that.