Vendors can help

[Carl B.]

I purchased a one owner 6,883 miles 87 Z-52 coupe. This car was pristine and unmolested,but it would barely run.The check engine light came on and off,with backfiring and black soot out the exhaust.We changed both fuel filters and the spark plugs,no change.At times it would clear up,check engine turned off and it ran like new.Sounded like an ECM issue to us,so we delved into the problem further.No code were found after diagnostics.I had ordered catalogs from all the major vendors and they arrived shortly after the car,lo and behold the jumped out from one of them"the 27c256 chip or EPROM in your memcal does not have an indefinite life.The data or calibration will begin to deteriorate after15-20years,causing many running issues in your Corvette.Bingo! The original prom can be reprogrammed(with upgraded and changed info),or you can purchase an aftermarket chip.Four days later,the new chip arrived and 30 minutes later the car was running better than new.Now,5 years and 19,000 miles it is still a great ride. Thanks for your time,Carl

[Mark E.]

Re: Vendors can help

I've haven't heard of ECM data or calibration deterioration. Is it possible the ECM deteriorated with age? Heat, corrosion, bad solder joints,...

Watch for injector issues; they're old and may not be compatible with ethanol.

It sounds like you have an exceptional 1987; can you post photos?

[Tom E.]

Re: Vendors can help

Mark,
Ive worked with cars and electronics for years and had never heard of an ECU deteriorating either however, do a web search for “27c256 chip deterioration” and you will find a fair amount of information on EPROM deterioration. Apparently it’s not uncommon. I think it’s great when people share odd experiences like this otherwise a valuable piece of data gets lost.
Tom