Heat Soak problem w/81
Thread Starter
4th Gear
Joined: Jul 2005
Posts: 4
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Heat Soak problem w/81
I was wondering if anyone can tell me how to get codes from an 81 vette with a feedback system. This one does not have an ALDL so I'm kind of lost. My problem is if I start the car from cold it will run all day with no problems, but if I shut the car down and restart it the check engine light will come on and will not idle unless I give it some gas. I've checked ground at the computer,done a full tune up(plugs, wires, cap rotor, O2) and I even changed the ign module as well as done the patented "GM" wiggle test at all the electrical connectors. I'm starting to get frustrated as I have little working knowledge of the early GM feedback system.
TIA
Ian
TIA
Ian
Safety Car
Joined: Jul 2001
Posts: 3,921
Likes: 2
From: York PA
The ALDL connector should be under your ash tray. All you have to do is ground the one pin. If you cennector is missing you can ground the wire at the ECM. If you don't have a GM shop manual yet you should get one. It has a lot of valuable information about the CCC system. Also Doug Roe has a book about Rochester Carbs that has a whole section on rebuilding/tuning a E4ME carb and aditional info on how the system works. 
Safety Car
Joined: May 2001
Posts: 3,758
Likes: 3
From: Surrey
A couple of longshots here, but they're simple things worth checking (if you haven't already):
Is the choke coming on when you start it from hot, either partially or fully? I had a bad connection on the PCB behind the dash which caused the choke to stay on when the engine was hot. The check engine light was permanently on as it was seeing a rich condition. A mechanical hangup on the choke could also cause the same type of thing.
Second thought is that you said it was OK after giving it some gas (which made me think that the choke could be snagging up & the movement/shock/jolt/airflow caused by giving it some gas could be freeing it up). It could also be that giving it some gas is getting the O2 sensor up to operating temp. After shutdown the sensor rapidly cools down & needs to be heated up (to about 600*????) before it starts giving good readings. When was it last changed? It may be that the sensor is on the way out.
As stickboy said, the shop manual is brilliant.
When did the problem start? Was it after anything had been done to the car?
Is the choke coming on when you start it from hot, either partially or fully? I had a bad connection on the PCB behind the dash which caused the choke to stay on when the engine was hot. The check engine light was permanently on as it was seeing a rich condition. A mechanical hangup on the choke could also cause the same type of thing.
Second thought is that you said it was OK after giving it some gas (which made me think that the choke could be snagging up & the movement/shock/jolt/airflow caused by giving it some gas could be freeing it up). It could also be that giving it some gas is getting the O2 sensor up to operating temp. After shutdown the sensor rapidly cools down & needs to be heated up (to about 600*????) before it starts giving good readings. When was it last changed? It may be that the sensor is on the way out.
As stickboy said, the shop manual is brilliant.
When did the problem start? Was it after anything had been done to the car?
Thread Starter
4th Gear
Joined: Jul 2005
Posts: 4
Likes: 0
I just changed the O2 about a month ago. The car had been sitting for about Four years and when it was first started(after the four years) as soon as the car went into closed loop it would die an instsnt death and would not restart. I unplugged the MCS on top of the carb and it would run perfect(a little rich though). So we changed the fuel and did the tune up as mentioned in the first post, after changing the ign module it changed the problem from instant stall in closed loop the the problem i'm having now. I am going to get the service manual for it.
Ian
Ian
