RPM Stair Steps On Deceleration?

[Smoked]

New to me 2005 5.9L.

The truck has only a 4-inch straight pipe and a small muffler.

I have never been tuned (So I was told) for a decent maintenance record.

I noticed yesterday that under everyday driving, the RPM would not drop smoothly when deceleration; I did hit one hill, and i tried going around a vehicle while 75 ish, and the RPMs just tanked; I never could get power, so I got my foot out of it, and I the truck started driving normal again. (not towing).

Since then, I have just been taking it easy on her.

I checked in neutral, and sure enough, the RPM will skip and stutter, coming down from 2100-ish with a smooth climb up.

It starts quickly with no smoke at start-up, perhaps a little puff that I can even describe; it runs super smooth, with a slight "tic" that sounds more like valve lash than anything.

The truck has 180k on the clock, and I'm sure they are stock injectors.

New fuel filters and fuel treatments have not seemed to help it all.


Thinking it might be the injectors, but before I start throwing money on something that is not an issue, I wanted some other takes on what it might be.

Can a diesel shop run a scan and see what is going on?

Orrea, am I just being paranoid?

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[AK Bob]

New to me 2005 5.9L.

The truck has only a 4-inch straight pipe and a small muffler.

I have never been tuned (So I was told) for a decent maintenance record.

I noticed yesterday that under everyday driving, the RPM would not drop smoothly when deceleration; I did hit one hill, and i tried going around a vehicle while 75 ish, and the RPMs just tanked; I never could get power, so I got my foot out of it, and I the truck started driving normal again. (not towing).

Since then, I have just been taking it easy on her.

I checked in neutral, and sure enough, the RPM will skip and stutter, coming down from 2100-ish with a smooth climb up.

It starts quickly with no smoke at start-up, perhaps a little puff that I can even describe; it runs super smooth, with a slight "tic" that sounds more like valve lash than anything.

The truck has 180k on the clock, and I'm sure they are stock injectors.

New fuel filters and fuel treatments have not seemed to help it all.


Thinking it might be the injectors, but before I start throwing money on something that is not an issue, I wanted some other takes on what it might be.

Can a diesel shop run a scan and see what is going on?

Orrea, am I just being paranoid?

Injector ball wear can cause a slow return to idle.

A diesel shop can check the injector return rates to verify.

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