automatic "choke"
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Member
Joined: Aug 2012
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automatic "choke"
I have a 91 f150 with a 302. The motor is basically brand new, but just recently it's been acting weird during start up on cold mornings. It's almost like the automatic choke isn't working. Before you bash me... yes, it's efi, but I seem to remember in the past that it would kind of increase the rpms on it's own when I would start it on cold mornings and I could basically throw it into gear and drive off.
Now, it starts just fine, but if I try to drive anywhere right away I need to blip the throttle to keep the rpms up and sometimes it will die when I put it in gear. Once warmed up its perfect
what am I missing? Is there a sensor or something I should check? Please help.
Now, it starts just fine, but if I try to drive anywhere right away I need to blip the throttle to keep the rpms up and sometimes it will die when I put it in gear. Once warmed up its perfect
what am I missing? Is there a sensor or something I should check? Please help.
Senior Member
Joined: Jan 2013
Posts: 2,225
Likes: 90
From: Gonzales, Texas
If its not idling right, check the IAC, may need some cleaning up. Other than that...alot of em do it. My 91 302 does and it runs just fine, been doing it since i got it and that was many many miles ago
Senior Member
Joined: Aug 2010
Posts: 2,669
Likes: 116
From: Long Beach, CA
To set the record straight its not the technically a choke but the effect is essentially the same. Its referred to as cold start cycle. The fuel trim activates at a preset rich level and the idle air control controls the incoming air until the engine temp warms up and the ecu counts to a specific time. Fuel trim is then controlled by the O2 sensor and the MAF or map system. The major difference between that and a choke is that the choke on the carb limits air inlet and where efi increases fuel, but again the effect is virtually the same. Just a little info.
Senior Member
Joined: Nov 2012
Posts: 177
Likes: 8
To set the record straight its not the technically a choke but the effect is essentially the same. Its referred to as cold start cycle. The fuel trim activates at a preset rich level and the idle air control controls the incoming air until the engine temp warms up and the ecu counts to a specific time. Fuel trim is then controlled by the O2 sensor and the MAF or map system. The major difference between that and a choke is that the choke on the carb limits air inlet and where efi increases fuel, but again the effect is virtually the same. Just a little info.
