I have a 1992 Z28 305/AT. I was having problems awhile back with eratic starting and idling and charging issues. I replaced the battery, checked the alternator, replaced the ICM, replaced plugs and wires. Anyways, I just replaced the ICM today after not driving it all summer or even messing with anything. Put it all back together, and it fires right up.! Nothing erratic. Sooooo, I think all is well. Take it for a test drive and let it heat up. Get back home, shut it off and....it just cranks and cranks and doesn't catch. So, I pull the #1 wire off and do the spark test after it has cooled off. It fired right up without the wire being on!!! So, now I pull it up to the garage and try and start it again. Same freakin' thing, just cranks! ANYBODY HAVE ANY IDEAS????

 

What would make the timing marks jump around when holding a timing light to it. It jumps from anywhere between 5* and 8* with it more stable on 6*.

Do you think it could be a rotor/cap problem or coil???

 

a bouncing timing mark is either a timing light pickup thats grabbing the signal of a nearby spark wire or other electrical interference, or slight variation in rpm ex. vacuum leak etc

some searches in google pulled up that it might even be that your balancer might have rotated on you (key broke or slipped out) it wouldnt change where the mark was but it would cause a wobble or some other such that would throw off the timing

it'd say its the light

 

Thanks JPEDEN. Anybody else have any ideas on the hot start problem? Cap and rotor? Coil? ECU? Maybe a sensor? BTW, I took all the SMOG stuff off a couple years ago.

 

Ok. Since nobody has any ideas. Can anyone point me in the right direction for an OBD I scanner? Nothing fancy, I just want to know what to replace instead of replacing everything. I don't have that kind of cash. Thanks!

Also, if it is my computer (ECU), would the scanner still work?

 

In case anybody is interested, I just replaced the cap/rotor, and coil. Seems to have fixed it. Along with a new ICM, but that didn't help with the starting.

 

Thanks for the update. So a new cap, rotor, coil, and module cured your no start when hot issue?

Only reason I ask it because of this line right here:
"Along with a new ICM, but that didn't help with the starting."