Hi,

I just got a bunch of work done on my bus, '93 6.2 Chevy G30. New IP, timing chain etc... At start up I get bluish smoke and a very low rumbling idle. I have been searching this forum and getting confused by the number of terms used for different idling functions. What I would like to know is how to increase the idling at start up. Is that the cold idle, fast idle??? Once it is driving it is fine. What do I need to touch to get it idling faster at start up only? Can someone describe where the component is?

Thanks!

Rif

is it just the fist start of the day or all of the time? the idle is controlled by the screw in the fast idle solenoid. it's located on the drivers side of the IP. one more thing, make sure the solenoid works before anything else. it controls the cold/fast idle.

hope this helps

Cool. I just got it back, but for sure the low idle is at first start up, but I think when I dropped off my children at the bus stop this morning the idle was also low, not as bad as at starting though. What is the easiest way to make sure the solenoid works? And will I have to take off the intake manifold to get to the fast idle solenoid? Thanks!

rif

There are really only two idle conditions: Fast idle on and fast idle off.

The fast idle consists of a solenoid which is switched on when the engine is below ~120 degrees F. The solenoid holds the throttle open just slightly when it is on. It is not strong enough to open the throttle by itself, so you must "set" the fast idle during a cold start by holding a little throttle while you start the truck. The fast idle is required to maintain a steady idle during a cold start, if it is not functioning you may get a low idle speed during a cold start.

The fast idle solenoid works in conjunction with the cold advance or HPCA (Housing Pressure Cold Advance) system. This works off the same power wire that feeds the fast idle solenoid, and is therefore on whenever the cold advance is on. The HPCA system advances the injection timing slightly whenever it is on to speed engine warmup.

The fast idle solenoid is outside the injection pump, mounted on the driver's side of the pump, easily visible with the hood open. It is cylindrical, about 1.25" diameter, maybe 2" long. It has a green wire going to it and a flathead adjustment screw in the middle of it. This screw adjusts the fast idle speed, and must be adjusted with the engine running and the fast idle on.

The HPCA solenoid is located inside the injection pump and also has a green wire going to it. The wire goes to the top of the injection pump and is also visible with the hood open. Other than making sure it is hooked up, I wouldn't mess with the HPCA system.



When the fast idle/HPCA systems shut down as the truck warms up, the fast idle solenoid will retract and allow the throttle to close against the throttle stop. The stop is a small flathead screw down rather low on the driver's side of the pump, underneath the fast idle solenoid. It is hard to see, and rather hard to access if you have cruise control. This screw is used to adjust idle speed when the engine is warm.

The proper idle speeds are ~600 rpm with the fast idle off, ~800 rpm with the engine fast idle on.

If the fast idle is working and you leave the truck idle after a cold start you will hear it drop down suddenly as it warms up (may take several minutes before this occurs). If it doesn't, first test for power to the solenoid with the engine cold. Pull the green wire off the solenoid and turn the ignition on. This should give you +12v at the green wire. If it doesn't, trace the wiring back and look for cut wiring etc. There is also a temp switch which could cause the problem. If you aren't getting power to the fast idle you're probably not getting power to the HPCA system, which could cause the problem you describe.

To test the solenoid itself, start the engine, disconnect the green wire from the solenoid and use a jumper wire to supply +12V direct from the battery to the solenoid. Then press the adjustment screw in with your finger to manually set the fast idle. The solenoid should hold the adjustment screw in and the idle up.

To set the fast idle, do the above procedure to set the fast idle using a jumper wire, then use a flatblade screwdriver to turn the adjustment screw and set the fast idle. Once you release the power to the fast idle the engine speed should return to the slow idle speed.

To set the slow idle speed, disconnect the fast idle/HPCA wiring, then use a screwdriver to turn the slow idle adjustment screw.

Awesome thanks!

Rif