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Discussion Starter #1
I thought I had cleared everything up but guess not.

Ran KOEO and pulled 41 and 43 from memory.

43-o2 sensor indicate lean at full throttle
41-no o2 sensor switching detected -always rich

what do these generally mean?
 

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Focus on code 41 first.

Fairly simple test to verify if its a bad sensor is to remove passenger side 02 and put it in the driver side. And Driverside 02 in passenger side. Re-run codes and see if code 91 shows up.
 

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Discussion Starter #5
I also just discovered I have no thermostat. That's nice!

Not. I live in FL, its summer now and temps are on the rise. Should I put a 195 back in there?
 

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Discussion Starter #6
I'm glad to say it isn't my sensors, but a much bigger problem.

Fuel pump.

I remember back in Feb I had the same codes and it was my fuel pump, it just slipped my mind and I forgot about it. I took a gauge to it and ignition on, I get 25 psi and it slowly drops. I start the car and it goes up to about 33 psi. Under heavy acceleration it kinda fluctuates but more so drops more than rise.

I think I know what it's time for.
 

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Discussion Starter #7
I'm glad to say it isn't my sensors, but a much bigger problem.

Fuel pump.

I remember back in Feb I had the same codes and it was my fuel pump, it just slipped my mind and I forgot about it. I took a gauge to it and ignition on, I get 25 psi and it slowly drops. I start the car and it goes up to about 33 psi. Under heavy acceleration it kinda fluctuates but more so drops more than rise.

I think I know what it's time for.
 

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Since you live in sunny land I would probably go with a 180 as down here in Miami it is hot and always humid.

Did you already replace your fuel pump in Feb?
 

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Discussion Starter #9
Sounds good.

I didn't. I was having performance issues then and come to find out my distributor was off a tooth, so my fuel pump totally slipped my mind until I recently did the self test again.
 

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With the engine running and no vacuum on the regulator, what does the Fuel Pressure read?

Granted a fuel issue would explain code 43..... But....... Doesn't mean its the pump all the time. Fuel Filter of Regulator could do the same thing. As well as Injectors.
 

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Discussion Starter #11
Remember this 89coupe?

allfordmustangs.com/forums/5-0l-tech/282154-90-stock-5-0-code-43-lean-wot.html

Posted it back in Feb in you actually commented on it.

Psi numbers are still the same as what's there.
I've never switched fuel filters, and to my knowledge when I got the car, the guy did state the fuel pump was changed. To what or why, he didn't know.
 

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Ahhh!

Like I said in that thread. At 34psi the injectors no longer provide the correct amount of fuel for WOT conditions. Injectors flow rates are based on 39.15psi. In that sense it looks like you only have 17.7lb injectors assuming the injectors flow like they are new. Thats close to a 7% loss in injector size and close to a 13% loss in fuel supply. Unless my math is retarded, which is very well could be! :laugh:
 

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Discussion Starter #13
Definitely just spoke Spanish to me, but yikes!

My injectors are orange, from my understanding those are the 19lb (stock) injectors yeah?
 

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What I'm saying is that with the fuel pressure being at 34 PSI, they no longer send fuel like 19lb injectors. They are sending fuel like 17.7lb injectors. Or even less depending on the condition of the injectors.
 

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Discussion Starter #15
Oh boy. Guess that leads to only a few things? Filter which I highly doubt and last time I was under the rear, looked brand new. Or the trusty fuel pump?

I definitely don't want to fall into the category of just throwing money at the car. But maybe the pump they installed was the wrong one? Or its just blah.
 

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Well the fuel filter may look new but could be clogged or old inside plus that is a cheap and easy fix. Now the pump will require a bit more work but not too much just make sure you try to run out as much fuel cause that tank can get heavy.
 

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Discussion Starter #17
Fair enough. I should know better. Motorcraft filter only runs $13 at my local auto parts store. Wouldn't hurt to pick one up I guess.

Also, if I were to do the fuel pump, would a 255 be the way to go? I've seen many use these. However, I have no future power adder plans for the car. Should I just throw a stocker in there?
 
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