Engine/Transmission (1998.5 - 2002) Rough Idle

[Kingram]

Hello,



I have searched for similar issues, but haven't found anything exactly like I'm experiencing.



Since I had my VP44 replaced about 3 months ago, I have had a rough idle. It seems to get worse after it is warm. When I stop and let off of the throttle, the engine will idle back to 1000 rpm's for about 2 seconds, then idle on back to about 800 or so and stay there. While it is idling, it has almost a miss to it, enough to vibrate the truck. I've also noticed when I'm coasting with no throttle but in gear at about 25-35 mph, it runs rough also. I can feel and hear it almost cutting out.



All of this started right after the VP44 replacement and did not exist before. I have not replaced or checked any sensors or touched the valve lash yet. I have good fuel pressure (10-14psi)



Once I'm under throttle it runs fine. No miss, good power and the same mileage I've been getting since new. No codes either.



2001, 130,000 miles, Non-HO, 5spd. , RV injectors and nothing else. I do have an ebrake.



Thanks for any advice,

Chris

 

[Graphic man]

where did you get the pump from?

i would talk to them and see if they will exchange it, i have hear of new pumps doing that.



Scott

 

[Me808garam]

Or maybe air in the line try opening the lines to injectors and cycling the pump.

 

[WestTN]

It is possible that some dirt got into one of the lines. It doesn't take very much to partially plug an injector.

 

[Kingram]

Thanks for the replies.



Scott, I was afraid of that. It seems to be something with the pump. I bought it from my local dealer. I will approach them about the problem. I should have called them sooner though. Of course, I have about 10k on the pump and they seem to be only good for 60k, so I'll be replacing it again soon enough!



If it were air or dirt (which it certainly could be) wouldn't it show up under throttle also? It runs fine except at idle.



Thanks again!

Chris