Volvo 3.0 High Idle

[PJFWH170]

New to the group. 2000 Volvo 3.0 runs great except idle won't go below 900 in gear. Occasionally diesels at shut down. Will be doing a tune up on the weekend and would like to know if I should adjust the idle mixture ( carb still has the plastic caps on the idle mixture screws ) or leave as is. I'm also unsure of when to apply 12volts to the adaptor plug on the distributor when timing the engien. Is it before starting the engine or after. Should I suspect an intake manifold leak ? Is it also necessary to use an external tach to verify the RPM ?

 

[Don S]

Re: Volvo 3.0 High Idle

Idling at 900 will cause a 3.0L to diesel for sure.
Disconnect the throttle cable from the carb linkage and adjust the end of the cable out to put a slight preload on the cable toward the idle position when in neutral.

 

[PJFWH170]

Re: Volvo 3.0 High Idle

Throttle cable has been removed altogether and the only way to get the idle down is to pull the carb linkage closed. It will stay at the lower idle until I throttle up and then won't come down to a lower idle unless i pull it back manually. It takes quite a lot of pressure to get it to come down.

 

[Don S]

Re: Volvo 3.0 High Idle

Have you tried adjusting the idle speed screw on the carb?

 

[PJFWH170]

Re: Volvo 3.0 High Idle

The idle speed screws are still covered with the plastic caps from the factory. It obviously hasn't been adjusted since new. I was going to try that as a last resort. I'd like to check the timing but don't know how I could do that without getting the idle down to 65-750 in drive ? Should I break the caps and try adjusting the idle considering that the wear and tear on the engine ?

 

[Don S]

Re: Volvo 3.0 High Idle

The idle speed screws are still covered with the plastic caps from the factory.

Those are the idle MIXTURE screws, you need to find the idle speed screw on the linkage.

Look for a screw with a spring on it near where the cable attaches to the carb.

 

[PJFWH170]

Re: Volvo 3.0 High Idle

That' the very first thing I tried. It's backed right off completely.....................not even touching the linkage. There's nothing physically preventing the carb butterfly from closing completely but not enough to slow it down.

 

[Don S]

Re: Volvo 3.0 High Idle

Will it slow down if you remove the cable from the linkage, the lightly push the carb linkage toward idle. With the cable off, there is no spring to push it to idle. Push lightly to idle and turn the screw some more counter clockwise.

 

[PJFWH170]

Re: Volvo 3.0 High Idle

With the cable disconnected and the idle speed screw backed off completely away from the linkage, the idle speed sits at around 900-1000. At this point, the butterfly is closed ( I've taken a screwdriver and pushed down on the butterfly to make sure it's seated closed ) but when I apply more pressure manualy to the linkage, I can get the idle down to about 800. The butterfly is not loose on the shaft. There's nothing mechanically out of wack that needs adjustment. I'm wondering if there's an air leak somewhere that's creating this problem or could the idle mixture need adjustment considering the caps are still on the carb and it's never been adjusted since new.

 

[Don S]

Re: Volvo 3.0 High Idle

I would have to agree with the air leak, might try squirting some oil around the base of the carb where it mounts on the manifold and see if the engine slows down.