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Flooding out while idling

944 Views 5 Replies 5 Participants Last post by  EagleAutosports
I have a 1991 Mustang 5.0 LX. It has Cobra fuel injector on it. Just bought the car. It runs strong but will try to flood out while idling. Any ideas what may be causing this.
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The computer should go closed loop at idle and look at the HEGO sensors to set mixture. The "adjustment" has limited range however. Larger injectors can result in the EEC not being able to bring the fuel within range.

A second thing that can cause this is excessive idle fuel pressure. The fuel regulator should have a vacuum line to the engine manifold vacuum. This line reduces fuel pressure when engine vacuum is high. Some aftermarket regulators do not monitor engine vacuum.

Assuming your HEGO (oxygen) sensors are good and the computer is going closed loop and has normal idle voltage (below 1.2 volts) from the throttle position sensor, it is probably injector size or fuel pressure.

By the way, I had good mixture using 19 lb injectors with 300-350 RWHP. I only have 39 lb injectors now with a supercharger making over 450 RWHP. Bigger injectors do not always mean more power.

Thanks for the info. I just bought the car so I don't know a lot about it. This gives me a good starting point though.
what mods do you have? The cobra injectors are 24# and if you got stock heads or a close to stock motor, their prob too big.
The problem is more than likely from having 24lbers, on a stock ECM. Need the Cobra ECM, or a Calibrated MAF, or a TUNE.
The Cobra injectors are 24's, so find out if the meter is meant for use with 24's, and if you actually need them. Is the rest of the engine stock or modified?
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