Warm idle issue

[ptoro01]

Hey everyone,

For the past few days my m117 engine has had a really rough idle when its warm. At first I thought it was the tranny acting up...fluid splashing but then I flushed the tranny and it stopped doing that after a little while. Now the problem has come back in the past few days. When the engine is warm, the idle just drops from 850 or 900 and jumps around badly and often all the way down to 400 where the engine is halfway dead. What could be the problem here. It is dangerous driving it like this because the engine could stall itself at any stop light. Is it my tranny thats causing the paddling. When I shift it from d to r the rear end moves up and down slightly and when i come to a stop it seems to be doing the same. But the rpms visibly drop from 900 to 400 and then back up to 1100.

Help me out please, I thought the problem was gone but its back to haunt me again.

Peter

[WANT '71 280SEL]

Checked the usuals such as plugs, wires? How about timing? Does this have the famous trigger points"? Not the ignition points, but the trigger points for the EFI? Keep those 116's alive!
Thanks
David

[300SDog]

Vacuum sensor and electic fuel regulating solenoid maze of complicated gadgets is my guess. Did you see Greg Bambo's and Art Dalton's excellent discussion on missing when cold and the more primitive 6 cyl IP vacuum valve?

Sorry I can be of no more help, but somebody more knowledgable with the 4.5 should have the answer. A list somewhere of sensors and solenoids that oughta be picked from junkyard cars would be helpful, rare and endangered parts, that can be swapped and traded here on the forum.

The problem sounds related to fuel/air ratio at idle to me.

[MunichTaxi]

Vacuum Modulator at the transmission. If the diaphram has failed, you will lose vacuum. If there is ATF fluid in the line when you dicconnect it, the diaphram has failed.

[ptoro01]

Thank you for the replys im gonna check on everything... I dont think that my car has the trigger points but the wires and ignition seem to be messed up a little.

I did mess around with the idle mixture screw back in march and i dont know what setting i left it in. It didnt seem to make much difference and it didnt all this summer.

The problem appears every few stop light. I dont know if its from the bad streets and a misconnected wire or a vacuum leak somewhere.

MunichTaxi, How do I check the vacuum modulator at the tranny. What other symptoms would this give. If it happens every few stops then I doubt that its this piece of the puzzle.

Thanks everyone I will check tomorrow morning and see what happens.
Peter