Ok, my friend drives an 86 camaro sports coupe with a 305 that still has all its computer controlled stuff hooked up and working. Anyway, we were driving yesterday after he filled up his tank. It took 14.6 gallons. So we drove a little over 60 miles and the car is driving perfect. All of a sudden the rpm gauge goes crazy and the car dies. We crank it for a while before getting it going again and manage to get it to a gas station. We couldn't get the car to stay on anymore after that. It was a strugge to get it to turn on. It would crank easily, the carb was getting gas and everything else was normal. The only thing my friend could think of is bad gas. The times it would actually turn on would be accompanied with a ton of black smoke coming from the exhaust. We let the car sit for an hour and when we turned it back on it fired up like normal and drove about ten miles before the rpm gauge went crazy again and just died out. This morning we checked the plugs cause we knew they'd be fouled from all the bad gas and put new ones. The car started right up but did the same thing again. We took out 10 gallons of the "bad" gas and put 5 gallons from another pump. The car seems ok as of right now. What would've caused this?

 

Wildly fluctuating tach=ignition problems. Id suspect a bad module to start with.

 

would the ignition still cause this even though the car is running right now? we did take out the gas and the car seems to be working fine right now, but then again it did give me 60 miles on 2 gallons of that other gas. how can i make sure its the ignition module?

 

Bad gas will rear it's ugly head shortly after leaving the gas station, not after 60 miles. And it won't be intermittent. Ignition modules are famous for crapping out and leaving you stranded then mysteriously working fine once your car is towed to the shop.

 

alrighty then, thanks a lot, i'm gonna tell my buddy to go get himself an ignition module, how hard is it to change that, is there any steps i have to take to change that? about how much do those things range from? is there any specific or recommended module he should get for his lg4 cc qjet 305. everything works in his car so let me know, thanks.

 

hotrod or carcraft recently did a story on a GTA they are working on. They had a similar thing where car would crank healthy but would not stay running right (or didn't start at all, don't remember).

They noticed that tach needle never moved when they were cranking. They guessed that ECU was not getting RPM signal and starting tracing that all the way to the ECU module itself. Eventually they replaced the ECU and everything started working fine.

Not saying ECU is faulty in your case, but you mentioned that tach was going like crazy when that happened, so I thought I'd share this.

 

hey that sounds interesting, but i don't know if that would be the problem, i mean the tach moves and everything when i'm trying to start it, and once it starts it runs great but when it is about to turn off it goes crazy. also we disconnected the computer and the car also did the same, it would start and then it would turn off. ok, let me go over this again, all this happen to the car yesterday, today it did it again and we took out the fuel, and as for now the car is running good. i didn't know that 305 could run that hard, but it is running good. i think it would be the ignition module, because this had happened to the car like a month ago, but it started like 15 minutes after and it had been running good since then. just yesterday it did it again but that time it no longer wanted to run, and today i ran it like 2 miles and it was running good, should i run it longer to see if it is the module or should it be replaced? one more thing, i also changed the plugs today, and some were coming out really black, but it wasn't oil, and the others were worn regularly.

 

I'm going with ign module also. They usually (I emphisize usually) work ok till they get hot, then they will do all kinds of crazy stuff. Like dimented24x7 said, the tach needle jumping around is a good clue.

They are pretty easy to replace, but you will definately want to use some heat sink compound on the bottom side when you install the new one. Without the heat-sink compound they won't last very long.