really bad idle

[patEOD92]

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?

[Kurbycar32]

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

[siteunseen]

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.

[240260280z]

What do plugs look like?

[Diseazd]

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, 2014 by Diseazd