Have I been "HAD"?
 

I'm new to the diesel world, so forgive my ignorance. I just purchased a 99 2500 with 180k miles. The previous owner said there's never been issue one with the truck.....should have raised the red flag then? Long story short, 3 days after buying the "check engine" light pops up, there's a slight surge in the motor, and the tach jumps around like a cat on a hot tin roof. I plan on pulling up the codes later on in the week, but can anyone give me a heads-up on what to look for? Any and all help would be greatly appreciated.

Tach jumps around while idling or while cruising down the highway?

The tach and the motor surge is both. Could it be a TPS? The guy I bought the truck from bought it with 102k on it, so he's put 78k on it in 10 years. He said the injector pump has never been replaced.....to his knowledge? Bring on the pain!

Need to find out your fuel pressure, and start saving for a good aftermarket lift pump. Does it surge when it is cold or just when it is hot or all the time?

You can try an APPS reset; below is an attachment that will walk you through the process.

Is it auto or manual? Just so I understand correctly, the tach jumps around all the time? I'm trying to rule out the torque converter going in/out of lockup if it is an automatic.

H.R.D: I never noticed it happen when the truck was cold. I'll find out shortly.

Bryce, the tach and the motor surge "both" happen whether the truck is in gear or parked.

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It's an automatic trans.....sorry

my tach bounces when idling, I think most of these trucks do it, so thats nothing to be too concerned about.

I mean it bounces from zero to 2 or 2500 hundred rpm's and it feels like a gas motor with a skip when it does.....just to clarify.

If it does it only when it is hot, 95% sure your IP is going out.

Check out the thread below, especially the video and see if yours is doing that. If so it could be CSS or CPS.
https://www.dieselbombers.com/24-val...r-problem.html

sounds like a crank sensor to me.:hellox: