Misfire accompanied by erratic tach

[Boulder Bob]

Last year my tach started mildly bouncing around at the correct reading plus or minus 200 to 400 rpm. The car ran fine. Now I have developed a misfire that seems to happen in synch with the tach bouncing.

Some accompanying symptoms: often it won't idle normally - it runs at a fast idle. when this happens the tach will bounce around between 2000 - 3000 rpm. The engine isn't running this fast, but it's running rough. when it does idle at idle speed and I rev it to around 2000 rpm under no load it acts the same way - bouncy tach and rough running.

It seems to do fine under full throttle acceleration. Not noticing a misfire or performance degradation. I do feel a slight misfire cruising at 75 mph in top gear - just not as smooth as I remember it being.

Some weird stuff: there were occasions when it idled fast and I slammed the deck lid down (a respectful slam), it would return to idle. It has stopped doing this. It also seemed like it returned to idle when I tapped the rpm transducer. It has stopped doing this also.

Can anyone suggest where should I start with my diagnosis?

thank you.

[Chuck Miller]

Bob,

The first thing I would do is is check your points (if you still have'm) and make sure they're not fried, the gap is right, and tight.....

Next is pull off the tech to distributor wire (black with a purple tracer) clean both spade and connector and re-hook-up...

Hope this quick stuff is it........you might get luckey

[Fishcop]

Coil issue?

[304065]

Points. Check gap and dwell replace if necessary.

[66S]

Could be an alternator, regulator or other intermittant electrical problem. A volt meter would help detect that.

[Boulder Bob]

Could be an alternator, regulator or other intermittant electrical problem. A volt meter would help detect that.

thanks - I will check voltages once I can set aside a little time to do some diagnosing