Hi folks, new to the forum here. I've got a bit of a stumper on my hands here, so if you'd read all I have to say (I will try to be as succinct as I can) and give some input, it would help me a lot.

I received a 1990 Dakota from my neighbor yesterday. It's a short bed (with a color-matched canopy), cab-and-a-half, two wheel drive, five speed truck with the 2.5L TBI motor. The neighbor is the first owner and I am the second. It was his daily driver until about a year ago, at which point it (very suddenly, which is important) crapped out. I don't have many advanced tools on my hands and I'm working out of my driveway in Washington state... During the winter. If any of you live in the northwest you know how it can be in the winter, so I'm asking for advice here after a fair bit of self-diagnosis and repair so that I might be able to avoid getting sick working on a free truck.

The truck has a difficult start, and immediately wants to stall unless you get on the gas, at which point it backfires loudly and repeatedly. As soon as you lift off the gas it stalls and dies. It has very little power. The motor shakes quite a bit upon startup. I've taken a peek into the throttle body and there's unburned fuel sitting at the bottom of the intake manifold--the butterfly valve is wet, as well.

When it was given to me, it was throwing four codes: 12, 14, 25, and 55. 14 and 25 I have since resolved and will explain, 12 and 55 are meaningless. 14 was a MAP sensor fault code, and 25 was an Idle Air Control motor circuit code. I replaced the MAP sensor (it was $30, really no big deal) and code 14 disappeared, then I did an ECU reset in addition to unplugging and cleaning the connectors on the Idle Air Control Motor to solve code 25. A new code has since appeared, code 41 (alternator code), even though the symptoms have remained exactly the same as they were from the beginning. Nothing has changed even though I've fixed trouble codes that would normally point out the problem(s), so the problem is apparently elsewhere.

I have some further ideas as to what it could be, but before I dive into any huge repairs or spend any more money than I already have. I want to flip this truck for profit, so the less I spend the more I make.

Here are some ideas:

Fuel. I've heard bad things about the fuel pumps on 87-90-something year Dakotas, and I'm not sure if the fuel pump on mine was ever replaced. I don't know if the throttle body was ever properly serviced either, and that means the internal pressure regulator could be bad. Same with the fuel filter, or the single fuel injector. Clogged anything means running lean, which means backfiring, and potentially rough starting.

Spark. This is the less likely option, in my opinion. Old spark plugs, a worn distributor...

Timing? The P.O. said he had the timing checked not too long ago, and once the motor is running I don't hear pinging or clattering--it just wants to stall and die.

Vacuum? I've checked all the lines relatively well, but... Still always an option.

One thing I want to emphasize, that might help someone come up with an idea. The P.O. told me the truck ran perfectly fine up until the moment the problems began... It was a very sudden change. Popping, backfiring, no power, and you have to keep RPM's high at all times (where it backfires loudly) to keep the motor running.

I'm sure all of you have far more experience with this generation of Dakotas than I do, I'm generally more involved with Jeep XJ's than anything else. Known weak points related to this problem, any previous solutions, any ideas at all, really... Will be greatly appreciated, thanks in advance.

 

I'd lay odds on valve timing; camshaft belt jumped a cog.

But I don't KNOW that ... it's just what that sounds like.

I'd also pressure check the regulator to make sure it's at the nominal 14.5PSI that TBIs want.

DO do the plugs, wires, cap, and rotor, in any case.

RwP

 

I never really thought about the timing belt but Ralph is probably correct.

You know that a lot of these never get the timing belt service they deserve. In fact I wonder how many owners who bought the 4 cylinder trucks actually realized that there was a timing belt to replace?

At any rate I would inspect the timing belt and check to see whether everything is in the correct position. If it's not just replace the belt and tensioner and you'll be good, after all the parts to do it are very cheap.

This is very unusual truck IMO, the early 4 cylinder trucks are usually standard cab / short bed, which stands to reason because of the low power 4 cylinder, but here we have an extended cab 4 cylinder. Your truck was actually the one I started out looking for but after not finding any of them out there I assumed Dodge did not install the early 4 cylinder in the ext cab version.

At any rate post up some pictures of it, would love to see it.

Steve