DB2 idle adjustment - lower RPM when hot?

[WarWagon]

Just adjusted the idle down from 1100 RPM on my 93 project truck. Cruise control cable too tight was holding the idle too high I found. Sticker says 700 RPM, 800 cold. Have it at 850 cold with cold advance and 750 RPM warmed up. Checked the cold advance was off during hot adjustment.

After letting the truck sit hot it will start and hold 400 RPM or less. Bumping the throttle does not help it get the idle back when released. After running some the idle speed is back to where it needs to be.

Is there a low speed (idle) governor on the DB2?

What is causing this? Worn IP? Bad injectors?

 

[Acesneights1]

I'm no expert but I think there is a metering valve that sticks on these.

 

[6.2 turbo]

There is a flat spring on the governor arm that is supposed to change the idle with temp. On the main governor spring there is a soft spring at the end that sets the amount of governor surge ,like when letting the clutch out on a manual truck.

 

[Acesneights1]

I wasn't sure. I have a couple dead ones on the bench I have been meaning to dissect.

 

[WarWagon]

So I set the idle speed with the engine hot? And then if it drifts 3-400 RPM I have a IP issue with that internal spring. Looks like this would explain what is going on.

I have checked for binding on the throttle.

One would think it is a simple set screw setting. Frustrating when it doesn't work.

Idle also drifted around when it was high at 1100 RPM.

But at 174K and sitting around for a couple years who knows what is still good or not.

The sticking metering valve IP is sitting on the parts pile from my last blown 6.5...

 

[Acesneights1]

What were the syptoms from your sticking metering valve IP ?

 

[WarWagon]

Would stall when throttling down to idle. Would restart immediately. So accelerate and then take foot off gas and it would slow down the engine and stall out while I was still moving. Would randomly but repeatably do this. After a stall revving up the engine and releasing the throttle would stall. But letting the throttle off slowly would keep it running. Had 7 PSI at water drain and new fuel filter.

Bumped the idle up to 850 and rebuilt injectors cured the problem till the engine scuffed a piston and burned a hole in it some 25K later. Had a shaky idle though. The replacement 6.2 engine/IP ran a lot better.

 

[Missy Good Wench]

Really sounds like the IP needs to visit the Pump medics and get an Overhaul.

The advance piston bores wear out on these as do a few other items.

With a fresh IP the thing will work sweet.

Once you start seeing these little anomalies, its a tell tale sign that the IP is in the autumn of its life.


Missy

 

[WarWagon]

Thanks for the info. The pump will be removed with Mr. Massive Blowby engine and the 'spare' will be put in. Has to cool down outside first before this project.