After working on the 240 for 4 months and thinking i had it good i found i was wrong. It is idling so bad, ive tuned it and its great when driving but it vibrates really bad when idling and sounds awful. Any suggestions?

causes of bad idle, in order of probability

vacuum leak

vacuum leak

leakage of vacuum

carbs out of sync or adjustment

weak or out of time ignition. cap/rotor/plugs/wires/timing

cylinder/valve leakage, check with compression test

testing all of the above and finding a vacuum leak anyway

Go to an auto parts store and get a loaner vacuum gauge. I put one on mine yesterday, new to me car, and it pulled 17 hg at idle after replacing all the rotted lines.

What do plugs look like?

Make sure the choke linkage isn't stuck under each carb. Reach under each carb and push each nozzle upward. A stuck choke makes for a miserable idle and is fairly common in the Hitachi carbs. If one or both are stuck, your plugs should be black.

Edited May 26, 201412 yr by Diseazd