golfradict

I get an intermittent check engine light on my 81 only when decellerating or sometimes at idle at a red light. It comes on for maybe 2 seconds and goes away. I've changed the O2 sensor and also checked all the grounds I could get my hands on. The car is completely stock with 23K miles. Any help appreciated

my 76 ray

Go to an auto parts store and have them put their scanner on it. Autozone does it for free.

MelWff

I doubt they do OBDI scans, they do OBDII scans. If you google you will find the paper clip method of reading the code but I dont know if it remains in memory once the light goes out.

golfradict

Thanks man that is correct, they only do OBDII scans. I did the paper clip method as described in the shop manual and it shows all is normal. The code doesn't remain in memory, I wish it would just stay on.

MelWff

No other symptoms?

golfradict

When the light comes on the RPM's drop off some, definately pulling a load from some source. For example, at a red light it's idling at 800 and smooth, the light comes on and the idle is rough and drops off to about 600.

7T1vette

An intermittant code will not register a fault in the computer memory. Such an occurence indicates that there is some 'marginal' issue with a sensor or component...but not one that is a problem for the engine.

I would suggest that you check the EGR valve for carbon build-up/clogging and (perhaps) remove and clean all the ECU connector terminals AND remove/clean any ground connections going to the ECU.

If that doesn't solve the intermittant CEL flashes, whatever is going wrong will eventually 'throw a code' to the computer. At that point, the CEL will stay ON and you can get a code dump from the OBD-I terminal to guide you as to what needs help.

golfradict

Thanks for the info, this should give me a real good starting point.

wajulia

You can check the codes without a reader. Pull the ashtray and you will see an empty connector. With the key on, engine not running, short the two pins closest to the driver, you will see a slot in the connector between those pins that lets you slide a small screwdriver into the connector and short the pins

You will hear a clicking in the engine, it is the mixture solenoid in the carb and it is normal. The check engine light wil begin blinking. It should blink once, pause, blink twice. This is a code twelve. It will do that three times. After the twelves, it will blink out a set of codes. For example, Two blinks, pause, four blinks is code 24. It will blink out the code three times. It will repeat with any other codes and end with a series of 12's again. It will repeat this as long as it is on and shorted
Write down the code or codes. You can get a list of obd1 codes on the internet. The service manual has very good troubleshooting guides on each code. If you need a copy of the troubleshooting tree,let me know

I have seen people waste a lot of time and money randomly changing things without reading the codes. Read the codes and there are a lot of people that can help you do proper troubleshooting to find the problem

Most of all, don't give up hope, it is usually pretty straight forward finding and fixing these problems

Good luck and let us know what you find

wajulia

Reading the thread agAin, if you get no codes, I would clean the connectors and the pads on the ECM. If you don't know it is behind the drivers seat next to the battery which helps the connectors get pretty corroded.

My suggestion is to use DeOxit. It is a little pricey but does a great job at cleaning corroded connectors. You can find small cans of detox it at radio shack

Good luck

SIXFOOTER

This is what you need

golfradict

Man thank yall guys, 7T1Vette, Wajulia, Sixfooter, for all the valuable information.

golfradict

Just wanted to follow up on this post back in October 2013. Thanks to the advice from 7T1vette my check engine light finally stayed on and I was able to pinpoint a problem that has been pestering me for the past year. I was the throttle position sensor in the carb that went bad, this also fried my O2 sensor that will be replaced also when the parts come in. Will have to replace the top plate gasket on the carb also. ~Randall

Brians1

One other item for you, as a fairly new 81 owner, and having fully traced out the CCC, the best advice I got after I got tired of counting "blinks"..I went on e-bay and for 10 bucks got a fully operational OBD1 Code scanner the GM Techs used back in 81. It’s called an "OTC Monitor 85". best part is that is scans real time believe it or not. I highly suggest you grab one on e-bay. I spent 10 bucks on buy it now and 12 in shipping - 22 bucks and now I can see my CCC controlled timing while driving, O2 operating temp, etc, etc. and just for kicks what I always laugh at now when I use the scanner I want to call it “old” but I was One when that thing came out – so I’m backing off the word “old” :P
best of luck

golfradict

Great thanks, will definitely search eBay for one of my own