Hey guys I need some advice and help,

I recently purchased my first vette. it's an 1981 corvette, previously a California car. I live in TX and we don't have too many restrictions here so the previous owner took all the smog stuff out of the car. the car is pretty much stock with 75K original miles. Headers with side pipes were added, and it's pretty much straight pipe.

The check engine light in the car is always on. Car start right up and drive pretty decent but i can tell it's not running perfect and a bit too rich. I took the car to a corvette shop around town and they told me that they couldn't communicate with the ECM in the car therefore we don't know what the codes are or why is the check engine light is on. I can see the O2 sensor connector is of course unplugged and hanging underneat.
and i am not sure if that is what cause the problems.


I know I have the option to either find out whats the problem is possibly replace the ECM unit and run it stock like that, or I have the option to take the whole ECM unit out and put new carb, manifold, distributer etc and run it like they did prior to 1981.

I do want eventually to try and get more power out of the engine and i know the ECM doesn't like Cams and aftermarket parts very much so I am not sure what to do. Is there an aftermarket ECM unit that can be manipulated or tuned to run with mods??

any advice or help from you guys is welcome!
thank you very much

 

First off...you can pull codes WITHOUT a scanner. It can be achieved manually.

You have to sit down and figure out what you want out of the car. You need to pull numbers and see actually what you have now. You might be surprised in what you have and what you want and how to get what you want may be quite an adventure.

If your headers do not have a port for the O2 sensor...that will be an issue.

I am not aware of a ECM that can plug right into your wiring that processes faster and gives more capabilities.

Preforming a compression test and verifying that you do not have excessive compression 'blowing-by' the rings and the PCV system can not keep up....thus excessive crankcase pressure.

DUB

 

If you still have the original factory installed digital radio, all you need is about an 8" piece of wire.

The connector is under the ashtray, in the console. Once you find the connector, you jump across two of the terminals, and any stored codes will flash on the radio face. If the car originally came with the base analog radio, the test procedure was the same, but I think the Check Engine Light blinked the code(s) instead.

I forget which two terminals you need to jump, and my shop manual's at my store. If you need the info, I can try to post it tomorrow.

 

Has the previous owner already removed all carb and Distributor stuff that works with the ECM.

The computer controlled Carb will have two electrical connectors on it, one on the top of the carb, front, passengers side -- that is the AF solenoid. The other will be on the drivers side , front, half way down the body -- that is the TPS. If those connectors are not there, the carb has been changed out and the ECM is not doing anything anyway.

The deistributor should have a four pin electrical plug coming our by the firewall drivers side. It should have NO vacuum advance. If it has a vacuum advance -- it to has been replaced with a PRE-ECM model. Again, if this is so, the ECM is not doing anything.

Take a picture of the top of the engine with the air cleaner removed and I can probably tell quite easily.

If the CCC and the Distributor have been replaced and the car is running good -- take the light bulb out of the CEL and enjoy your corvette. You can put it back to original if you want, lots of time and money and only worth while if you want an original 81

 

The "Check Engine" light will flash....or at leash every one I have worked on did flash when manually checked.

The 2 terminals are at the end of the connector...where there is NOT divider between them...so you can basically use a thin flat blade screwdriver and join the two with it and read the codes via the Check Engine light flashing.

DUB

 

Thank you guys for the responses.

Compression test has been done and the results were good. engine is in good shape. i know the previous owner did a rebuilt of the top end.

Everything is stock according to him. stock carb, stock distributor. nothing have changed, but i can take a picture later.

my main question according to some of you guys experience and knowledge is if I should try and get that ECM issue fixed or the best thing to do would be to pull it all out.

I guess my main goal would be for the car to run better with a possibility of gaining more power out of that 350 lol

 

Ok number one you have to have your O2sensor connected. I have sidepipes on my car . I added a bun to on of the pipes in the header before the collector. Without the O2 sensor the ECM will not work with the CCC it is either all or nothing . So if you do not to use theecm simply change the dizzy and carb to a non CCC and you are good to go