Constant high idle
06-22-2013, 08:04 AM
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Join Date: May 2013
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Constant high idle
1980 Datsun 280zx 2+2 N/A 201,000 miles.
I recently developed a constant high idle (the same day I had it aligned at a shop but probably a coincidence)
Anyway, it only does it when the car is completely warmed up. I start the car and it idles fine until I race the motor and then it stays at 2200 rpm and will sometimes fluctuate back down but is constantly high for the most part.
I know my air regulator is bad because I took it off and tested it. It's stuck closed so I just drive it like it is. Today I removed the hoses from the regulator and blocked them off and it still idles high when gas is pressed. (There was a little air getting through the regulator) If I remove the blockage then the car idles low again and you can hear the air releasing, but when I block it again it does the same thing. Do I just need to replace the regulator? I thought you could bypass them. or is something else causing my problem?
I have been running with the air regulator unplugged for a few months with no issues. Why all of a sudden is my idle so high?
Other things I have tried include removing the oil cap while car is running to check vacuum (it nearly stalled), I disconnected cold start valve, I checked all plugs and wires, cap and rotor.
I am not a mechanic and if I am missing something please help.
UPDATE!
After looking online and performing various tests everything seemed to be pointing to the BCDD. Some people said they removed them and a few said they adjusted them. So I figured what the heck, I will adjust it even though the FSM does not recommend it. Well, I turned it several turns clockwise until the idle finally dropped down and I drove it around for a while, making sure it was completely warmed up. It seems to idle very good. I have it set a little high at 1000 rpm's (which I adjusted in the idle screw on top) because I have the air regulator disabled. This should allow for a decent morning idle. I will start the car in the morning and see if I can bring the idle down just a hair but as it is I am happy with how it is idling and driving.
What I don't get is that it was running fine before. Why all of a sudden did I have to make adjustments?
I will leave this up in case someone else has any issues like mine.
I recently developed a constant high idle (the same day I had it aligned at a shop but probably a coincidence)
Anyway, it only does it when the car is completely warmed up. I start the car and it idles fine until I race the motor and then it stays at 2200 rpm and will sometimes fluctuate back down but is constantly high for the most part.
I know my air regulator is bad because I took it off and tested it. It's stuck closed so I just drive it like it is. Today I removed the hoses from the regulator and blocked them off and it still idles high when gas is pressed. (There was a little air getting through the regulator) If I remove the blockage then the car idles low again and you can hear the air releasing, but when I block it again it does the same thing. Do I just need to replace the regulator? I thought you could bypass them. or is something else causing my problem?
I have been running with the air regulator unplugged for a few months with no issues. Why all of a sudden is my idle so high?
Other things I have tried include removing the oil cap while car is running to check vacuum (it nearly stalled), I disconnected cold start valve, I checked all plugs and wires, cap and rotor.
I am not a mechanic and if I am missing something please help.
UPDATE!
After looking online and performing various tests everything seemed to be pointing to the BCDD. Some people said they removed them and a few said they adjusted them. So I figured what the heck, I will adjust it even though the FSM does not recommend it. Well, I turned it several turns clockwise until the idle finally dropped down and I drove it around for a while, making sure it was completely warmed up. It seems to idle very good. I have it set a little high at 1000 rpm's (which I adjusted in the idle screw on top) because I have the air regulator disabled. This should allow for a decent morning idle. I will start the car in the morning and see if I can bring the idle down just a hair but as it is I am happy with how it is idling and driving.
What I don't get is that it was running fine before. Why all of a sudden did I have to make adjustments?
I will leave this up in case someone else has any issues like mine.
Last edited by Red1980zx2+2; 06-22-2013 at 04:13 PM.
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