In advance, thank you for any comments or suggestions. I deeply appreciate any help in diagnosing this problem.

My 99 cummins, (237,000 miles) has started having a funny problem. I can crank the engine and as soon as I hit the thottle it sticks for a second and the rpms shoot up to 3200. When the rpms hit 3200 the thottle releases and the rpms drop back to idle speed. After this happens, the engine won't rev past 1200-1300 rpms. I can disconnect the negative post on my batteries and reset the computer and the truck will act normal for approximately 100 miles before it begins acting incorrectly again. Overall, the engine is very strong and performance is good when this problem is not occuring.

Kindest Regards
GuntownDiesel

 

I do not know what is causing it to do the 3200rpm but it sounds like after it does that the truck is going into LIMP mode (will not throw codes). It is the safety feature that limits the trucks power if you do something stupid like over rev it or over heat it.

Thinking about it when was the last time you replaced your APPS? Have you check the wiring leading from it?

 

The TPS looks original. I had a spare laying around that still works fairly well, the same problem is occurring with that spare TPS. Will check wiring etc.

Thanks for the input!