The issue started like 5 months ago. When going at highway speeds the truck suddenly jerks, its quite hard not like if when you take your foot off the pedal but like if it totally cuts out ignition or fuel

• Only happens at speeds above 50
• Seems to only happen after the truck is warm
• Seems to only happen while I’m accelerating, specially going uphill, never happens decelerating
• If im driving slow, city type driving it never does it, not even when I have the bed loaded with stuff or while im going thru steep hills
• Once it does it it recovers itself almost immediately although some times if I try to accelerate right after it keeps doing it over and over again. When its doing it, after it recovers a can hear the engine pinging for a very short amount of time.

I first thought this was some sort of sensor so I replaced

• Crank Sensor
• camshaft position sensor (the one that goes on the distributor)

Problem still present



I thought spark was the issue so I replaced

• Spark plugs
• Spark plug wires
• Coil
• Distributor Cap
• Distributor Rotor

Problem still present



So if it was not spark I thought fuel.

I connected a fuel pressure gauge to the manifold and it was a tad under 50 PSI the whole time (FSM states 49 so it is perfect) I took it for a drive with the fuel pressure gauge attached to the fuel rail and was able to reproduce the issue but the fuel pressure was 49 when it happened so fuel pup/fuel rail pressure is not the problem.



This weekend Im going to run a Mopar combustion chamber cleaner on the engine, I’m thinking that maybe there is carbon build up causing detonation at highway speeds and udder load??? However not holding high hopes for this to do anything for me….



Any help would be greatly appreciated as im running out of options or ideas on what to do next….



Maybe fuel injectors?

Sensors on the throttle body? (TPS, etc)?

 

Will it still do it if you disable overdrive? (assuming auto trans.)

 

Havent tried disabling overdrive, will give it a shot.

I forgot to mention on my original post that the truck runs as good as always, have not decreased mpg or have any CEL. Everything seems fine apart from this...

 

I would suspect fuel pump are you having longer than usual startups? Longer startups were my fist sign my fuel pump had a problem then a few cut outs. A shop tested the pump and just couldn't tell it was going bad they kept testing it driving it but still nothing I told them just replace it.

Results no more problems

 

Yeah, this looks tooo much like a fuel pump i was about to replace it but first checked the fuel rail pressure and looks ok, even drove with the fuel gauge and make the problem happen and the pressure was ok..... I might try it again

 

Check your u-joints.

 

Today i dissasembled the Throttle body and cleaned it, also took out the spark plugs and sprayed a can of mopar combustion chamber cleaner in the spark plug holes. Dont think that this will make any difference but will test it tomorrow, to late now to go out...

Here is a pic of the sparkplugs (about 6k miles on them). I dont see anything wrong on them, perhaps look like its running a bit lean?

 

as advised, if it does it again, turn OD off and see if it does it locked in 3rd gear. While very unlikely, it could be OD cutting in and out or the planetary trying to lock up.

 

Turned OD off and it still did it....

Not really sure what to do next, my list now looks like
1. take out the injectors and clean them
2. replace the oxygen sensor
3. replace tps sensor
4. replace map sensor
5. replace fuel pump ( i really dont want to do this, i did it like 4 years ago and its a pain to bring the tank down, besides i tested fuel pressure on the rail and looks ok...)
6. cut the catalytic converter, take it off the truck and see if the problem is that its clogged (although if this was the issue i would have acceleration problems most of the times not just suddenly for very brief periods of time)
7. toss the truck into a cliff and be done with it....

Any other ideas before i get to #7?

 

Skip the fuel pump, if pressure is good, that's all that matters. (and gas gauge works.....)

I don't think this is going to be a cat problem either..... as that would just be poor overall performance, not what you are experiencing.

As for #7, The EPA will take offense at that......

Do you have a scanner that can do data logging?