The engine jumps at 3,500 revolutions

Hi Samuel,

This sounds like you are on the right path because any time you can change a part and it effects the performance or issue, you know you are close. What I can't explain is why the RPM jumps at a lower RPM with a different sensor in it. I suspect that the aftermarket sensor is just simply different so it is causing the PCM to adjust the cam differently then the Mopar sensor.

Your engine is called a World engine and it is a variable valve timed engine. This means the PCM will more a cam shaft phaser to adjust the valve timing to the optimal setting for the given situation.

Couple things come to mind. Was anything recently done to the timing chain or valve train at all?

Did you just recently change oil weights? Go to a thicker or lighter oil? What oil are you using?

Have you checked for any air leaks in the intake system or possible vacuum leaks? It sounds like a lean misfire at higher RPM. Normally the cause of this is unmetered air getting into the engine.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

https://www.2carpros.com/articles/how-camshaft-variable-valve-timing-works

Can you get a video of the RPM jumping and hopefully that will trip some other ideas for me? Seeing it helps a lot. Thanks

Can you elaborate on the resetting of the timing? Why did he remove the head again (if he did) and what do you mean by turn the head? Did he mill the head or in other words, cut it down to remove a warp?

Also, when you are driving the vehicle and you accelerate does this happen or does this only happen when in Park?

Okay. I completely understand.

The thing that worries me is if you milled or cut the cylinder head so that it was no longer warped, that you have effected the timing of the engine.

Do you have any codes in the computer?

When the engine was timed, it should have looked like the attachment. You may want to remove the cover again and check timing. If you cut the head down, you should have offset that difference with a thicker gasket. I guess this can be done even though we don't have a specification but the piston to valve clearance has to remain because this is an interference engine which means they will hit each other if not timed correctly. Clearly they are not making contact but we still may have a timing issue.

Also, we have a rev limiter on this engine that should be set around 4,000 RPM. You are not getting there so that tells me the computer is possibly inducing this issue.

Hopefully you have some codes and that will point us in the correct direction. Thanks