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Senior Charter Member
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Discussion Starter · #1 ·
I had my car dyo two months ago, but im still getting these codes. Why? How can I fix it. My FAR looks good.

41- HEGO signal out of range/ always lean
91- HEGO signal out of range/ always lean

 

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Senior Charter Member
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The dyno run is at WOT and is open loop (O2s are ignored).

The codes indicate that when in closed loop (most normal driving) the O2s are lean. The closed loop AFR switches around 14.7.

Exhaust leaks, vacuum leaks, misses and bad O2s can all be possible causes.
 

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Discussion Starter · #4 ·
I was thinking about replacing them but since they were new I though it might be something else. I'll replace them this week.

I'll be there this year, I need to find a baby sitter soon. The wife may come this year too.

Thanks,
Charles
 

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Discussion Starter · #5 ·
Narve,
How do you check for Exhaust leaks and vacuum leaks?

Charles
 

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FFCobra Master Craftsman
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I personally think you have an air or vacuum leak because I had the HEGO 41-91 errors too when I had an air leak. I think 41 is left and 91 is right so it is unlikely that both of your 02 sensors happen to be bad at the same time.

Checking for vacuum leaks: Buy a can of sensor-safe carb cleaner (about $5 bucks). With the motor running, give a small spritz of carb cleaner around the lower intake seams, upper intake seams, air tube seams after the air cleaner, and vacuum lines. Basically, any seam in the air intake system. The engine will rev higher if it sucks in carb cleaner. This way you can find the leak instantly. Keep the carb cleaner away from the air cleaner so you don't suck in carb cleaner through the normal channels. You can block off areas with rags or tape when you start narrowing it down. Good luck.
 

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Discussion Starter · #7 ·
Thanks DMW, I will try that this week also.

Charles
 

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Discussion Starter · #8 ·
Update
I've checked for vacuum leak and I had it at a mustang shop but could not find a leak.
I also replaced the O2 sensors.

Im using another computer now and im getting code: 41 again and 85.

whats going on? :mad:
 

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Be sure the O2 harnesses are not swapped (passenger on driver's side...).

Make sure that the heater circuit has +12 Volts. If the O2s are not heating they will not work properly.

What MAF are you using? Is it aftermarket?
 

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Senior Member
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Interesting, I also get codes (41-91) plus Code 34 - Insufficient EGR Flow (KOER). Both Oxygen sensors are new (Bosch)! :confused:
 

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I believe there is an O2 ground on the back of the pass. cyl head. Make sure that it is connected and good. I think it is an orange wire.
 
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