240D won't return to idle - Page 2 - PeachParts Mercedes-Benz Forum

yellit · #16 02-17-2009, 12:02 PM

I think the old style IP,s had a little dipstick and individual oil sump....

The newer ones like I have is sharing the engine oil supply via that lower tube feeding the IP crankcase...

mplafleur · #17 02-17-2009, 01:03 PM

Quote:

Originally Posted by yellit

The newer ones like I have is sharing the engine oil supply via that lower tube feeding the IP crankcase...

This is what I thought.

OM616 · #18 02-18-2009, 12:46 PM

I have been too busy and or out of town for the last couple of weeks and just saw this.

I am real close to you, being in Wixom, and have done a tone of IP tuning on my 240D. If you still are having idling problems, I can explain what is going on and I have special tools to make internal adjustments if necessary.

When you rebuilt the engine you restored the power and the throttle settings for a worn out engine will cause a new engine to race.
The IP governor is actually four separate governors that use the same set of fly weights. They are the Idle governor, torque control governor, max speed governor, and fuel cutoff governor. The Idle governor is what you are working with.

The first thing you should do is soke the EXTERNAL idle speed screw and jam nut with WD-40 or equivalent. After letting soke for a while, loosen the jam nut and remove the screw to inspect the spring plunger in the end. If the plunger is working properly, is not sticking, then reinstall the screw and turn in until it just touches the throttle arm. Run the jam nut down so the screw can not vibrate down further. Find some one to help you, and start the car. With one person in the car maintaining the idle speed, have the other person back off the jam nut and turn in the EXTERNAL idle speed screw until it is controlling the idle.

Don't get to comfortable with the idle speed until the engine is up to full temp as the idle speed will creep as the engine warms up and it could start to run away.

You should find that there is a "window" in the EXTERNAL idle adjustment, where the external idle screw adjustment dose not change the speed very much. This is because the idle governor is trying to maintain a constant speed. If you adjust the external idle so it is at the upper end of the Idle governor speed the engine will not want to idle down quickly. The contrary is true. If the external idle set at the bottom of the Idle governor speed the engine will decelerate very quickly.

I found that my INTERNAL Idle governor speed setting was too low. When I had the EXTERNAL idle setting where the engine would idle down how I wanted, the engine would stall a lot. After adjusting the INTERNAL Idle speed setting, I can now control just how fast the engine returns to idle with the EXTERNAL idle screw. Returning to idle too quickly and it is hard on the synchronizers and clutch , too slowly and it is hard on the clutch and the engine is always one the verge of running away.

The thing to remember when making IP adjustments is that each adjustment effects the others and a balance needs to be maintained. Where that balance point is can be adjusted to change the performance. I have my Torque control turned in two turns, Rack limit removed, made High Idle (Max Speed) and Low Idle adjustments as well as the ADA replaced by a set screw, and I can still get my idle to come down faster that I want if I want to.

If you or anyone is interested I can go into further detail. I am also willing to come by and lend a hand. It would have helped me to have some one who had been there and done that when I was figuring out how it all worked.

mplafleur · #19 02-18-2009, 05:12 PM

OM616,

Thanks. We may be able to get out to the car tonight. I'm not sure who tightened the jam nut. Maybe it wasn't and the external screw walked down to the point where it doesn't want to idle down.

Will let you know.