I have a head scratcher for you. I have a “spare” 1997 Dodge truck, and what’s not to love about a 318 Mopar V-8, five-speed manual, 4×4-motivated truck for occasional use? Well, mine has a “random engine misfire” code. She runs like Jack the Bear for weeks, then stumbles, misses, and literally dies going down the road. Sometimes you barely turn the key and she’s running, other times, I crank for 15–20 seconds and nothing. After stalling when running, I’ll pull to the side of the road, mumble unkind things, turn the key and she starts.
I would get codes P0300, 0301, 0303, etc., but it changes to whichever cylinders misfire at the time. I also went through the Mopar TSBs (Technical Service Bulletins) and found the one to reroute the ignition cables to prevent “cross firing.” I have replaced TPS (new), engine position sensor (new), known-good used MAP, and distributor pickup. I ran an extra ground to the computer body. (I hate computers!) I ran for several weeks with a fuel pressure gauge connected and poking up on the hood where I could read it while going down the road (good pressure per spec), all to no avail.
That’s certainly a cool truck, especially with a manual transmission! So let’s get down to fixing this mighty steed ... Read the full article on Hagerty.com:
i have had people suggest contaminated fuel before, but always assumed with todays ethanol "contaminated" fuel, water would not be an issue. any idea why possibly faulty injectors would work well for several weeks and then not function correctly. the old girl does have over 345,600 kms on it. (thats 214,700 miles). would a computor from a 97 ram318 automatic work? i do have a good one of them.
In theory you can use the automatic computer but it will let you start the engine while in gear, and it could be tuned (air fuel ratio, timing curves etc) are different. Probably not enough to matter, but be warned.
Regarding the fuel injectors, you bring up a good point. So I would highly recommend someone tests them to see how far off from factory flow rates they truly are.
I didn't see any mention of the condition of the spark plugs or wires, and that would be the first thing I check. I've dealt with misfires on our 1983 Dodge Ram Van, 1998 Ford Ranger, and 2001 Mustang GT, and all were fixed with a new set of plugs and wires. Our Dodge would sit for months between times of use, and one time it unexpectedly ran poorly which you might think could be a problem with old fuel or the carburetor. With the Ranger truck, it was running poorly, and it was because of cheap plug wires sold at common auto parts stores that look nice, but didn't last as long as good name brand parts. When plug wires get old, they can seem OK, but not work.