My AC Puzzler
Thread Starter
Rennlist Member
Joined: May 2002
Posts: 9,243
Likes: 1,320
From: Roswell, GA
My AC Puzzler
This is not a big deal, but an annoyance. There seems to be a relationship between running my AC, turning it off and then the car running rich for a while. I had thought it was AC head related, but I have recently replaced it with a 928Int'l rebuilt unit.
Car: 1986.5 AT with 138k miles.
Summer scenario 1: Use AC for running around town. Weather is in the nineties and I stop into the local auto parts store and after 20-30 minutes go out to the car and start it. If the AC is on, the car will take longer to start as if flooded. Then as I drive I will see the Fuel Air meter full rich. After a few miles the meter goes back to normal.
Summer scenario 2: Same as above except not 20-30 minutes, but less than five. In this scenario there are no symptoms.
Recent Scenario: Use AC on a long trip from Nashville to Atlanta. Car runs fine. Coming off the interstate I shut off the AC. Within a mile of driving local roads or so I notice the Fuel Air ratio, while varying, is more in the rich range. Come to a stop light and as I pull away the car hesitates a bit and sure enough the Fuel Ratio is full rich. Continue to drive and after a few miles the Fuel meter is reading a normal range. On this trip I also had a symptom that may or not be related. Hypothetically, the car is going 80mph at about 3000rpm and I kick it down to third and hear pinging. This is not repeatable, so I am not sure it belongs to the AC problem.
These symptoms only appear when the AC is involved. The car runs a needle width or two above the first white line.
I believe that there is a problem with vacuum. I figure vacuum or the total lack of it could produce the rich running and the occasional hard shifting A/T. But, for the life of me I cannot figure out how. Unless, the vacuum reservoir gets totally emptied and has to recover. Leaky solenoid?
Anyhow, I am looking for suggestions. I plan on put a vacuum gauge inline at the computer this weekend. I'll try to watch it for any vacuum issues.
Car: 1986.5 AT with 138k miles.
Summer scenario 1: Use AC for running around town. Weather is in the nineties and I stop into the local auto parts store and after 20-30 minutes go out to the car and start it. If the AC is on, the car will take longer to start as if flooded. Then as I drive I will see the Fuel Air meter full rich. After a few miles the meter goes back to normal.
Summer scenario 2: Same as above except not 20-30 minutes, but less than five. In this scenario there are no symptoms.
Recent Scenario: Use AC on a long trip from Nashville to Atlanta. Car runs fine. Coming off the interstate I shut off the AC. Within a mile of driving local roads or so I notice the Fuel Air ratio, while varying, is more in the rich range. Come to a stop light and as I pull away the car hesitates a bit and sure enough the Fuel Ratio is full rich. Continue to drive and after a few miles the Fuel meter is reading a normal range. On this trip I also had a symptom that may or not be related. Hypothetically, the car is going 80mph at about 3000rpm and I kick it down to third and hear pinging. This is not repeatable, so I am not sure it belongs to the AC problem.
These symptoms only appear when the AC is involved. The car runs a needle width or two above the first white line.
I believe that there is a problem with vacuum. I figure vacuum or the total lack of it could produce the rich running and the occasional hard shifting A/T. But, for the life of me I cannot figure out how. Unless, the vacuum reservoir gets totally emptied and has to recover. Leaky solenoid?
Anyhow, I am looking for suggestions. I plan on put a vacuum gauge inline at the computer this weekend. I'll try to watch it for any vacuum issues.
Three Wheelin'
Joined: Jan 2002
Posts: 1,560
Likes: 2
From: Maryland
Tib,
How does your volt meter look with the A/C on? How much "reserve" does your battery have?
I'm thinking a possibility of heavy electrical drop due with the A/c on due to load (compressor and blower) which can drop the battery voltage to a low point causing the brain to act funny. The voltage comes back up in time as the alternator catches the battery back up after the innital drop. Easy to monitor the car's voltage with a VOM from the cigatette lighter socket with a simply made adapter.
just a "stab in the dark"
Greg
How does your volt meter look with the A/C on? How much "reserve" does your battery have?
I'm thinking a possibility of heavy electrical drop due with the A/c on due to load (compressor and blower) which can drop the battery voltage to a low point causing the brain to act funny. The voltage comes back up in time as the alternator catches the battery back up after the innital drop. Easy to monitor the car's voltage with a VOM from the cigatette lighter socket with a simply made adapter.
just a "stab in the dark"
Greg
