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Does anybody know how poor an '87 mustang engine will run without the O2 sensors hooked up. I plan to put them in (I'm still in the process of installing the engine), but I'm trying to diagnose the engine before I drive it to the welding shop. It seems to idle fine, but cuts out under a load. Would the O2 sensors cause this?
Thanks in advance!
 

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No O2 sensors will cause a rich idle mixture, and stinky exaust. The computer basicly ignores them over 3000 rpm or at wide open throttle. Check your fuel pressure while accelerating, sounds like you have a fuel supply problem.
 

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My guess is the problem is more than likely strictly because the O2's aren't hooked up. The engine is either running incredibly rich or lean (I forget which right off hand), and is simply dying because of it.

-Brian
 

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the computer looks for o2 sensor input in closed loop operation. when the motor is at hgih load it goes inot open loop after a second or 8, depending on the comp you have. it will run without o2 sensors forever, but it will likely have a nice check engine light illuminated, and stay in open loop the whole time. it may go into closed and just guess at the afr, but im not 100% on this. either way, its not your problem.
 

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It is not a chevrolet, fords don't have a open or closed loop. Since the O2 sensors are only used for fuel trim the computer will compensate but going to a preprogrammed routine going rich/lean. The main sensor is the map sensor if 86-88 or Map sensor. If either one of these is unplugged it will run but poorly.
 

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On 2001-12-31 20:45, windsoreight wrote:
It is not a chevrolet, fords don't have a open or closed loop. Since the O2 sensors are only used for fuel trim the computer will compensate but going to a preprogrammed routine going rich/lean
So you are saying Charles Probst wasted his time writing the chapter in his books that explain closed loop operation of the Ford EEC-IV system?
 

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Fords definitely have open and closed loop - that's the whole principle behind electronic fuel injection; to be able to adjust for varying engine conditions via sensor feedback. In Open loop, the computer uses pre-existing strategies to run the engine, while in closed loop, the computer uses strategies as well as various sensor feedback to optimize how the engine runs. Also, I think you mean MAP (Manifold Absolute Pressure) for speed density, and BAP (Barometric Absolute Pressure) for mass air systems. If they both used MAP sensors, there would be no need to distinguish between the two in your post.
 
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