Hello ladies and gents!
Got a good one for ya. 1993 Dak with the 3.9. Bought the truck a few months ago for my boy who just got out of the Marines. He loves this body style. Drove 100 miles to buy it and had no issues. Drove like a dream! Fast forward a few weeks. I tried to start it once a month till he.got back stateside. First time after purchase it started but ran real bad. Popping and backfiring through the throttle body and exhaust. Missing bad and will barely run. What the heck!?? It ran and drove amazing on the 100 miles trip home??
Prior owner replaced the fuel pump (it has 40+ PSI @ the rail). Water pump, timing set, NTK O2 sensor, gutted cat, belts, hoses etc etc. Checked dizzy and it is all good. Pulled intake and replaced all the gaskets. Replaced both coolant temp sensors. Replaced air intake sensor. Replaced MAP sensor, throttle position sensor, idle control valve and the ECM. Pulled #1 plug and brought it to TDC and checked dizzy timing again, all good!??? Replaced the fuel filter too just because. Replaced all vacuum hoses. Every once in a while it will start up and backfire a couple times then smooth out and run normal!?? Even had him pull the wiring harness down and check all solder joints and repaired.all of them including under the fuse box and both fuel injector solder joints.
We have pulled just about every hair from our heads. Totally lost at this point. The iac makes a loud hissing sound when it runs bad. Its quiet when it is running right?? Any ideas folks???
We have scoured the web endlessly without a hint to a solution.

 

Codes?
If you fixed the plenum gasket the IAC would probably be the source of the backfires IMHO.
What did you mean by "checked the Dist"? It sounds like you know but if you don't the Dist does not time the motor. That is done by the computer. The dist sets when the injectors fire in the cycle. They call it Setting Fuel Synchronization . It is designed to be done with a scanner that puts the RPMS up to 1K and then you dial it in to zero. Some say going + 1, 2 or 3 makes it run stronger. There is a manual method for doing this with the motor off.

 

Just pulled #1 plug and got it up on TDC on compression stroke to confirm rotor was near #1 terminal on the cap.

Its OBD1 so my Maxisys MS906BT does me no good. Did the key trick and only shows a 12 and a 55 code. Nothing more than disconnected 12v and end line..

Truck is driving me nuts. It really does sound like its out of time or running out of fuel.

 

If you have a friend with the right software for a SnapOn scanner (I'm awaiting the proper carts for my 1988 for my MT-2500 I bought used), there's instructions at Hughes on how to set fuel sync.

If not, there's always this article.

But yes, I bet sync is WWWAAAYYY off.

RwP

 

Thank ya brother Ralph! I will read that article and get back with the results.

Seems no one ever finishes a post nowadays.

 

I own a few Mopars here. I bleed blue but have never experienced this situation.

15 Durango
12 Chrysler T&C Limited
08 SRT Charger
07 Magnum custom
02 RT Intrepid
01 Chrysler T&C Limited
98 Neon Highline 2dr.
several A and B bodies.

Some say I am car poor!

 

*blink*

With that fleet, it'd be worth picking up a competent competitor to the current replacement for the MT-2500 (don't know the model).

RwP

 

I was actually looking at the Solus. Snapon guy wanted 3000 for a used one. He is the one that told me about the Autel. I have no regrets as it works well. Programs all modules and keys/fobiks.

 

Birds are programmable? I was never able to find the communication port...... trying to fit the connector on their beak just wasn't cutting it.... they would try and BITE me! Never saw anything even remotely resembling an OBDII port......

 

Yeah you got me before I fixed the bs autocorrect for fobik. 😂