I bought a 81 corvette going on 2 weeks now, 50,000 miles on it beautiful condition, drove it home from Cleveland Ohio to Canton Ohio was running really poorly got it home checked air filter and it looked like original air filter, changed out filter, plugs, and oil noticed a big change in the way it ran but still had a miss, changed out rotor and cap took a test drive still had miss and poor gas mileage and an odor of raw gas, tightened down carburetor, I'm not complaining but looking for a bit of resolve so here it comes, I got back into to start and test wouldn't start, So I tracked it down to a bad ECM and changed it out and she fired right up, great grab the girl and the dog head out for Cleveland get 60 miles from home and she's starting to overheat so I pull into rest area and let it idle to cool it down and just when I'm back down to normal operating temp it stall's, well she wouldn't start turned over ok but no start, flat bed it home on Sunday, nice piece of change, went to Summit Racing got all new wires, cap, rotor, coil, ECM, and resistor witch was really hard to find, now here is the main question I'm asking, when I rebuilt distributor I noticed the old distributor did not have the center ground on the 3 way clip where you plug up tach and battery on front part of distributor and three way behind it, would anyone know if that would have anything to do with the poor fuel mileage, it probably no doubt has something to do with burning up ECM's I'm sure someone has seen or heard something of this, really would like to hear an opinion before I burn down the garage and everything in it, if you read this thank you for your time.

 

is your distributer ecm controlled?It should be.I would check the timing and I would check for a vac leak .what mpg are you getting now.how do the plugs look?

 

ECM failures aren't overly common so if you have replaced 2 now within several weeks, I would suspect something shorting out the ECM.
I would get a factory shop manual for your 81' so you can trace down all the ignition related wires and hopefully find the culprit.

 

Thank you very much for your replies gentlemen, Mr. Ezobens, Also Mr. Terry 82. for reading my questions about my reoccurring problems in the distributor and ECM module ( in distributor ). So with conversation and talking and examining, I have found some things that may pertain to the problem more less than not but, one that has an actual scientific explanation, one I took the manifold shrouds off of the factory exhaust manifolds and found that both sides at the Y splits had cracks, not the main problem but may have had something to do with the start of there of. Nothing had changed since the day that this car rolled off of the assembly line including the air filter, I took the air filter out and she idled a lot better but noticed there was a slight miss, So first things I do is Oil change, new plugs properly gapped, no cross threads or cracked porcelains, hand treaded and tightened from underneath car, new cap, rotor, air filter, your basic tune up, take her a spin and it runs better, seems to have gotten rid of raw fuel smell but still had a slight miss, tooling along and she heats up so I pull over And idle till she cooled down a lot, then she stalled and wouldn't start. Got it home narrowed it down to the ECM in the distributor, replace it go down the road same miss, boom does it again, so this time up too Summit racing, New Taylor wire set, complete distributor rebuild kit, cap, coil, rotor, resistor, already had a lifetime warranty ECM from the Zone waiting, start rebuilding and come across a center ground prong missing in the original three prong connection, put it back together very carefully also using white electrical connection grease, since then I haven't blown the ECM but yet the miss is still there and I have also pulled ECM in battery box to clean all connections on board and plug connections. So, after talking to a Certified technician for about four hours at my house and looking at Miss Vette and finding cracks in manifolds, and finding no leaks in any of the vacuum lines by way of brake cleaner spray, He asked; Did you change the pickup coil? I said I did not and he explained that the computer ECM sends spark signal to distributor ECM and if that ECM cannot distribute spark too the plug it has too go somewhere and after enough of it at higher speeds it will burn out the distributor ECM, and while you have distributor out change the gear on the end of the shaft because it's nylon, but I guess we all knew that, RIGHT? 50,000 miles, I shouldn't be having problems like this, So live and learn Gentlemen, for what else is there to do when you're retired? and I would also like to thank Mr. Dub, and anyone else who helped me work on this or might have anymore information regarding Miss Vette, She's a Beauty for a tan "81"

 

good job staying with it .glad you got it going.

 

If you don't already have one, I suggest you find a copy of the Chevrolet Chassis Service Manual (or its equivalent for 1981 cars). There is a wealth of specific info regarding your car and the "one year only" electronic controls system which manages your engine. There is nothing detrimental about that system, as long as all the components are there and properly working together. But, you will need that manual to diagnose problems and to perform detailed testing in the future.

Also, that system should be OBD-I compliant; it should be able to give you trouble codes when the Check Engine Light (CEL) illuminates. That assumes that the CEL is actually working. If the CEL bulb is burned out (or removed/defeated), the ECM could be running in "open-circuit" mode (start-up mode) and never reaching closed-circuit status. That could explain the poor idle, performance and fuel mileage.