Cold Start
Thread Starter
Instructor
Joined: Apr 2015
Posts: 178
Likes: 49
From: West Plains, Missouri
Cold Start
I have a bone stock (as far as I know) 89 coupe, with 145,000 miles on it, that runs rich on cold start, rich enough that it will bring tears to your eyes. If you let it run for 5 minutes or so it will lean out and run as it should. I think I have read on the forum that a bad O2 sensor will cause this. I just want to bounce this off of you guys to see what your opinions are. Thanks in advance for your thoughts. 
Le Mans Master
Joined: Sep 2013
Posts: 6,192
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From: near the thumb in the mitten
Normally a code 13 should set for O2 not ready. If you have a way to monitor data I would make sure CTS is reading correctly a long with O2 sensor activity. O2 or coolant sensor could cause condition but with no diagnosis it is a guess
Team Owner
Joined: Jul 2004
Posts: 28,381
Likes: 3,262
From: Hartford WI
I have a bone stock (as far as I know) 89 coupe, with 145,000 miles on it, that runs rich on cold start, rich enough that it will bring tears to your eyes. If you let it run for 5 minutes or so it will lean out and run as it should. I think I have read on the forum that a bad O2 sensor will cause this. I just want to bounce this off of you guys to see what your opinions are. Thanks in advance for your thoughts.
A couple things I would check are the IAC on the throttle body. If it has crud blocking the "air leak" it might explain it? The other is the health of your injectors. If they are crudded up, the spray pattern might not be good and thus have a less than ideal combustion?
All this is assuming your timing is correct and CTS that the ECM sees is correct. To know that, I would time it at 6 degrees. Also, I would use an infra red thermometer and hit the sensor to see what it reads as cold and use a scanner to see what the ECM sees. They should be kinda close to each other.
Race Director
Joined: Apr 2002
Posts: 10,036
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From: Anaheim CA
I have a bone stock (as far as I know) 89 coupe, with 145,000 miles on it, that runs rich on cold start, rich enough that it will bring tears to your eyes. If you let it run for 5 minutes or so it will lean out and run as it should. I think I have read on the forum that a bad O2 sensor will cause this.
Conditions for closed loop mode:
Coolant temperature > 40.7°C = 104.4°F
Engine run time > 300 seconds (cold) if startup coolant temperature < 58.5°F
Engine run time > 206 seconds (warm) if startup coolant temperature > 58.5°F and < 158.5°F
Engine run time > 50 seconds (hot) if startup coolant temperature > 158.5°F
Oxygen sensor reading between 0.195 and 0.686 volts for > 10 seconds
300 seconds = 5 minutes. Does that number seem familiar?
Team Owner
Joined: Jul 2004
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From: Hartford WI
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
That's the temperature in my 1986 BUA EPROM. I checked the calculation to make sure. Other years/EPROM versions might be different.
Team Owner
Joined: Jul 2004
Posts: 28,381
Likes: 3,262
From: Hartford WI
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
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Thread Starter
Instructor
Joined: Apr 2015
Posts: 178
Likes: 49
From: West Plains, Missouri
Thanks guys for the responses, I got to thinking today (gets me in trouble) and I have never checked the timing on this car. Well low and behold it was set at 8 degrees, set it back to 6 now the car starts as it should cold or hot. Thanks again.
Team Owner
Joined: Jul 2004
Posts: 28,381
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From: Hartford WI
I would have thought that 2 degrees wouldn't have made such a difference. I would certainly paint a stripe on the harmonic balancer to see if it moves. On the older cars, the balancer has a habit of separating.