So my corvette has been getting terrible gas mileage ever since I bought it. I get about 6 mpg. The check engine light code is 51. Something to do with the memcal. I unplugged and replugged the ecm and the memcal chip and it’s still there. Is this the reason for my bad mpg?

 

51 says change eprom. if chip is in properly

this is a dupe of your other thread you abandoned

 

The style of connecting pins and conector/s they used on early CCC cars ...at the ECM were sometimes problematic. You might try unhooking and re-hooking the ecm. Also, make sure the grounds and ground path to the ECM are real good.

 

We are still waiting on pics from your 10/8 dupe thread to see what you got under the hood ???

 

At this point you should just get rid of the CC carb and distributor and put in a HEI and non CC carb. Easier to deal with.
If there is a problem with the ECM then it will be cheaper to convert then to fix it.
Unless this is a numbers matching show car.

 

Not the best advice, IMO. Just 'ditching' what you think doesn't work properly DOES NOT identify the cause of your issues. Throwing money and 'trinkets' at a problem is rarely a solution.

 

I personally wouldn't. I'd keep it stock. They run better stock. Better fuel economy and when working right should drive better. A good working CCC car will sit and idle perfect just about like an EFI car. That's because it's got a solenoid which electronically controls the idle mixture. Yep. People who battle carb issues wish they could have electronic control. Well you HAVE electronic control. Learn-up, Fix what you have if you're not looking for a lot of HP. The CCC is electronic fuel management. Most of the time they work great and usually doesn't give many fits. Look it lasted 40 years! Yer talking more work and expense to convert it...and what about your lock-up torque converter? Converting sounds good now, till you've spend a bunch of money and time and it still runs like crap, hesitation, you're back to dealing with smelly carb issues...and all that. People who drive modern cars forget about those cars, or weren't around to experience the joy. That's why a lot of car guys spend thousands of dollars in time/parts converting their Carb-cars over to EFI!! And that's a big time commitment. Well, like I say, you have electronic fuel management. Now dig in and fix it and you'll be back to good fuel economy and better running.

Do a bunch of general Google searches, not just for your code, or Corvette. You want to get info from other enthusiast websites too. They used the Computer Command Control (CCC) system on probably 10's of millions of cars, including on Square Body Impala/Caprices, G-body cars, Camaro and Firebirds ...all which have strong enthusiast groups out there. Do some searches beyond just Corvette.

Let me do some digging on the codes. There's all the info in the world on those CCC systems...well-written GM books on ebay, like THIS. There are others too.

Most of the time it comes down to basics... 1) Are the grounds all good? Esp on a 40+ year old car. Ground wire at the battery? Ground to Frame? Ground to certain parts of the body. Check the ground at the ECM. Ever see how rusty ground connections get? Even on car that come from desert locations. Start with the most obvious thing of all, which is one of the easiest things to check. There are various grounds around the body and frame. Do a google search for them. Good luck

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I just did a google search. Litterally tons of helpful links come up for code GM CCC Code 51. Here's one:

https://www.chevytalk.org/fusionbb/s...hp?tid/147527/

Get busy and start searching. The solution could be as easy as a bad wire...or even swapping out something.

I have carbureted cars. I wish they weren't carb'd though..... (something electronic be better IMO).


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