81 Carb problems
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Pro
Joined: Dec 2000
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From: Camino CA
81 Carb problems
My 81 has problems when it's cold (even on hot days) it will start, but it has a low idle and will die if I don't keep changing the throttle position, the check engine light is also on. Once it warms up everything works fine, no engine light.
I found that if I disconnect the 2 wire connector on the top of the carb, the car works fine all the time, but runs very rich and of course the engine light is always on.
What do I need to do to fix this? (I'm not ditching the computer and buying a different carb)
I found that if I disconnect the 2 wire connector on the top of the carb, the car works fine all the time, but runs very rich and of course the engine light is always on.
What do I need to do to fix this? (I'm not ditching the computer and buying a different carb)
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
Usual culprits are vacume leaks. A good cleaning may help the carb situation, make sure the choke operating correctly. How many miles? When was the last tuneup? Any mods? The fact that it clears up after warming up pretty much tells you the carb and comouter are working so thats good.
Race Director
Joined: Jul 2004
Posts: 12,696
Likes: 329
From: Scottsdale Arizona
Originally Posted by SIXFOOTER
The fact that it clears up after warming up pretty much tells you the carb and comouter are working so thats good.
This and the fact that disconecting the mixture adjustment solenoid makes it run fine but rich is exactly what's supposed to happen.
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Joined: Dec 2000
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From: Camino CA
I have headers and a heated O2 sensor, but those have been in there for a few years. I just put in a similar to stock crate engine, and I have a hollow catalitic convertor right now. The carb, computer and trans have 125,000 miles on them. I've already replaced all my bad vacuum lines, I have a rebuild kit for the carb that I was planning on using someday, so it looks like I have a project for next weekend.
Race Director
Joined: Jul 2004
Posts: 12,696
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From: Scottsdale Arizona
I wonder if the heated O2 sensor is the issue? How did you wire it up?
Until the engine is warmed up, I don't know if the computer looks for input from the O2 sensor, but I know that it's lloking for a rich condition. Would the heated sensor provide the same output as expected under these conditions? I don't know.
Do you have a correct and working sensor in the passenger side head? This is another switch that indicates that the engine is warm. Does your secondary fan (electric one) run all the time?
Until the engine is warmed up, I don't know if the computer looks for input from the O2 sensor, but I know that it's lloking for a rich condition. Would the heated sensor provide the same output as expected under these conditions? I don't know.
Do you have a correct and working sensor in the passenger side head? This is another switch that indicates that the engine is warm. Does your secondary fan (electric one) run all the time?
Melting Slicks
Joined: Mar 2006
Posts: 2,465
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From: Orange Park Fl
Sounds like a choke problem to me. I would advise you to e-mail Lars at v8fastcars@msn.com to get his choke set up paper before you start the rebuild. God bless, Sensei
Thread Starter
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Joined: Dec 2000
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From: Camino CA
The O2 sensor just has a 3rd wire that's connected to 12v when the ignition is on. I put that in because the 2-wire O2 sensor wasn't getting hot enough with the headers, and it wouldn't pass smog. I took it by the local college's auto shop to test that everything was working, and tweaked it to have passing smog numbers. The passenger side head just has a switch for the secondary fan. I have a plug in there because I have dual electric fans with it's own sensor.
I did all this over 3 years ago, and it ran fine for 2 years with that setup.
I did all this over 3 years ago, and it ran fine for 2 years with that setup.
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Race Director
Joined: May 2006
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From: Dayton, Ohio
You are veering away from stock and that makes it tough.The MC solenoids are able to be checked with an OHM but I'm not the best on these.I'l look at the book and see if I can find something.Sixfooter has an 81 maybe he can tell you how to check it.Did you read your codes?
Thread Starter
Pro
Joined: Dec 2000
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From: Camino CA
Here are my computer codes with descriptions, I don't think this tells us anything we don't already know.
12 - Normal Code
23 - Mixture Control solenoid is open or grounded
24 - Vehicle Speed Sensor. Disregard if set when drive wheels are not turning.
45 - Rich exhaust indicated by the O2 sensor.
12 - Normal Code
23 - Mixture Control solenoid is open or grounded
24 - Vehicle Speed Sensor. Disregard if set when drive wheels are not turning.
45 - Rich exhaust indicated by the O2 sensor.
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
Read the codes, it will tell you whats going on. Doesn't sound like the mods you have done would be a problem. Make sure choke is good, The O2 sensor might be a problem until its warmed up.
Start with the codes and go from there
Race Director
Joined: May 2006
Posts: 16,528
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From: Dayton, Ohio
Originally Posted by Ben Taylor
Here are my computer codes with descriptions, I don't think this tells us anything we don't already know.
12 - Normal Code
23 - Mixture Control solenoid is open or grounded
24 - Vehicle Speed Sensor. Disregard if set when drive wheels are not turning.
45 - Rich exhaust indicated by the O2 sensor.
12 - Normal Code
23 - Mixture Control solenoid is open or grounded
24 - Vehicle Speed Sensor. Disregard if set when drive wheels are not turning.
45 - Rich exhaust indicated by the O2 sensor.