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Runs rich when cold


roessel

Member
Joined
Sep 16, 2009
Messages
5
Vehicle Year
1986
Transmission
Automatic
I have a 86 Bronco II with a 2.9, it runs great when it get up to temp but runs rich when it's cold. I'm thinking there must be a sensor bad but not sure. Any ideas where to start?

Thanks
 
Depending on the area you live in and how cold it actually gets there it should run rich when cold and lean out when warm. Now if it was rich when it was warm then you would have a bad temp sender (the 2 wire sensor).
 
I have a 86 Bronco II with a 2.9, it runs great when it get up to temp but runs rich when it's cold. I'm thinking there must be a sensor bad but not sure. Any ideas where to start?

Thanks

I have an '87. Both the '86 & '87 have an EGR valve that is controlled by a relay mounted on the passenger side with two vacuum connections and a EGR sensor mounted next to the throttle control which also has a vacuum line. It is possible that the EGR is recirculating the extra rich exhaust gas while the engine is cold. The engine coolant sensor (two wire) controls the idle speed and injector settings so the comment above is also valid. I had trouble with the engine idle when it was cold but after changing the EGR, EGR sensor and the relay - it runs great.

freedom5
 

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