Help me smooth out my idle

[HMF]

Hi, my truck is running great with one small exception: The idle is a little rough.

I've had the truck for about 3 years and it has always idled like this. It is mainly just an annoyance since the truck runs great otherwise. I do not believe it is the injection pump, since I put a freshly rebuilt one on it a couple of months ago and the idle did not change. I do not see any smoke out the exhaust. (the IP is a mechanical DB2)

I was wondering if it could be injector(s). Could one, or more, injectors cause a slightly rough idle, but otherwise run OK with no smoke?

I'd appreciate any ideas on what might cause a rough idle and how to troubleshoot for it.

Thanks

 

[BigBlueChevy]

TDCO may be off at idle. Have you checked it lately with a scanner?

Is there any kind of knock or "odd" sound coming from the engine? Chances are if an injector is causing problems at idle it will cause problems up through the rpm's as well. Any loss in power noted?

 

[HMF]

Since this is a mechanical DB2, I don't think TDCO applies. But you might be on to something, could it be the timing adjustment?

I do not hear any abnormal noises, the power is good, and the engine seems to run very well other than this idle. Even this idle is not extremely bad, it is just a little annoying sometimes as it makes the truck have a jerking movment - say when you are creeping at a stop light, or parking.

Thanks

 

[matuva]

What is your idle speed ? Can you manually increase it on a DB2 ?

 

[BigBlueChevy]

good point. I'm not 100% familiar with mechanical injection so may be mixing a few things up here and there. whoops.

Timing adjustment though could be a problem. Matuva may be right with idle speed. to low perhaps?