94 5.2L Magnum running rough

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My daughter had a 92 Dakota 5.2 for a few years, maybe about five. It only ever smoked one CPS, and that is where I learned everything I know about EFI. lol
Eventually, my daughter couldn't afford to fix it any more so I bought it off her, and then I drove it for a few more years with a lotta fixing going on:
it smoked the coil,
and then the plate under the keg-intake blew a gasket,
and then the rad had to be changed,
and then the "posi" quit working,
and one by one the starter/alternator/and waterpump quit
and the idler went bad a few times, which smoked the belt.
and I had to replace the timing chain one time....
........ I loved that truck.......
But when she smoked a guardrail sideways on black ice one winter, well I wasn't gonna replace the frame, the cab, and the box yet also..... so off she went to the insurer.
 
Well, I spoke too soon. After running good in the garage with the new crank sensor, when I went to actually drive it, it started acting up again.
Swapped in a spare PCM that I have and it's not dying anymore. Unfortunately, it's a truck PCM that doesn't run well with the Jeep injectors/vacuum referenced fuel pressure.
The junkyard doesn't have any Jeep PCMs. Anyone have one laying around? I am starting a hemi swap this fall, so I don't want to pay a bunch of money to get this setup going again.
 
Look at your screen name. Put a slant 6 in it. Problem solved.
 
dartslantsix said:
My Barracuda has a 94 magnum swapped in from a Grand Cherokee. Stock injection.
After sitting through the winter, I started it and it's running really rough. It smells like it's running rich. It tries to idle down, almost dies, then idles back up. When I rev it up, it smooths out some, but not as smooth as it should.
Here's what I've checked so far:
No codes from the PCM.
Inspected all ignition stuff: Cap and rotor look good, plug wires checked out, plugs look good except #4 was wet with fuel.
While running, I pulled the idle air motor connector and nothing changed. Pulled #4 injector wiring, no change. Pulled the vacuum line to the fuel pressure regulator and it also didn't change anything.
My next thought was that #4 injector was leaking. Pulled the rails and pressurized the system, no leaks from any injectors. I ran the pump for quite a while and pulsed a few of the injectors with jumpers. They spray fine, nothing weird.

I'm stumped. My next step will be verifying fuel pressure. Other than that, it could be coolant temp sensor?

What else should I check?

Thanks.
-Dave
Click to expand...
Factory injection and computer?
Check the fuel sync. It could be out.. maybe the chain is stretched or maybe the distributor fuel sync phasing changed if it twisted 'wasnt tight'. I rough set mine and while doing that at one point I had wet plugs 'too rich'
 
dartslantsix said:
Swapped in a spare PCM that I have and it's not dying anymore. Unfortunately, it's a truck PCM that doesn't run well with the Jeep injectors/vacuum referenced fuel pressure.
Click to expand...

I am working on swapping a 5.9 into my '91 Dakota using '92 wiring harness and a '94 van 5.9 PCM.

None of the 5.9's in the OBD1 era run a return style fuel system, they all went to the returnless system with the FPR at the tank. But my '91 is setup with a return style system and doesn't have an FPR at the tank. This means there isn't a factory 5.9 PCM I can run that would just bolt in.

My plan has been to run the '92 fuel rail with the return line but remove the vacuum reference at the FPR on the fuel rail. Assuming the resulting constant fuel pressure provided by the '92 FPR without the vacuum reference is that same as what the '94 returnless system runs (pretty sure it is), the PCM will be none the wiser that it is running on a return style system. If necessary, I plan to adjust the fuel pressure using a screw through the vacuum nipple, but I don't think it will be necessary.

So, I would pull the vacuum reference off your FPR and plug is and see if it runs fine. I bet it will.
 
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