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I have a 1986 240GL with 330,000 miles on the original engine. I am the second owner and the car is in pretty good shape for it's age. Recently the car's thermostat stuck and being that the temp guage was not working at that particular time, I ran the car until it overheated and blew the head gasket. I pulled the head and had it milled and a valve job done. Additionally I replaced the cam seal and the timing belt at that time, along with the defective thermostat and the seal from the water pump to the head. I reassembled the whole thing using all new gaskets and the car started up. It was running a bit rough so i guestimated and tweaked the timing a little (I would guess with a cut of .018 for the milling job that a little less advance to compensate for the increased compression would be in order) as I didn't have a timing light at that time. the car ran fine for about 30 sec to a minute until I noticed that it was shooting oil out from under the valve cover. I cleaned the entire crank case ventilation system, replaced the flame trap and re-torqued the valve cover nuts and that cured the oil leak. I allowed the engine to run at idle for about 5 min and then frove it around the block. I immediately noticed that the car was idling way too high (with no tach it is hard to guess but ~1700rpms or thereabouts). When I brought the car to a stop the idle in park was very unstable varying up and down drastically (like it was possessed) and the idle did not respond at all to turning the idle adjustment knob on the trottle body. Next I removed cleaned and checked the idle air control valve. I was able to acutate the idle air control valve with it off of the car. I reinstalled the valve and there was no change in the car's situation. I removed and cleaned the trottle body and idle screw unit (didn't mess with the micro switch) I checked that the temperature sensor was functioning properly using the chilton's manual electic test at the ecu and at the same time I tested the micro-swith in the trottle body, both passed. At this point the car would run but still wildly. I attempted to pinch one of the hoses that leads to the idle air control valve and i could get a change in the engine's running but it was still unstable. My chilton's manual pointed to ignition timing being the only possible culprate remaining. When I borrowed a timing light and attempted to reset the timing I found that the distributor was very much stuck in place, but that the rotor was turning freely. In my frustrated attempts to free the distributor I broke the housing (which is quite fragile I might add). Once I glued the housing back together and replaced the cap and rotor the car would nto run at all. No spark can be had at the wire from the coil to the distributor cap. I ran through the chilton's checklist one last time and it pointed to a bad impulse sender in the distributor. I found a good used distributor and am awaiting the delivery of it. I was wondering if anyone can tell me if timing can cause the drastically varying idle (barely above stall to ~1700rpms)or if there is some other cause that I could be missing...possibly a vacume leak? Can i do the old fashioned test for vacume leaks with carb cleaner spray and listen for idle changes? I appoligize for the long detailed article here, but I am at my wit's end.
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