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My car club just got a '94 TBird donated for us to do a charity car build to raffle later this summer, and we are working on all of the maintenance things right now.

The check engine light is on and tonight I hooked up my autotap system to check the codes and I got Code P0174.

This is the description of the code from this website: http://www.troublecodes.net/Ford/eec-vobd2.shtml

P0174
System Too Lean, Bank No. 2

What does this mean? Bad O2 Sensor? Plugged Fuel Injectors? Bad Spark Plugs? Plugged Fuel Filter? Bad Fuel Pump?

What should we look in to first?

Thanks for any help. For more info on this project, check this out on my forum:
http://clubredline.net/yabb/YaBB.pl?num=1196575288

Thanks!:D
 

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One sensor code might indicate a faulty sensor.But I tossed the same code and replaced the sensor and still got the code.I later found the cause to be a vacuum leak.

Good luck.
 

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everything you mentioned could be a culprit...EDIT: including the spark plugs....even though there is excess fuel, the excess oxygen left over would be seen by the O2, and show Lean, not rich


start with the cheap stuff first.....

check for vacuum leaks

clean the MAF as per the Tech Articles, with electronics cleaner or MAF cleaner...you can find that for about $5 in any auto parts store....disconnect the battery or do the EEC-fuse trick to reset the EECs Keep-Alive-Memory so it can start learning from scratch again

replace spark plugs with autolite or motorcraft brand plugs

replace the fuel filter......if you can, have the fuel pressure tested with the vacuum hose disconnected from the fuel pressure regulator....should read 39 psi

dump a whole can of seafoam or Chevron fuel system cleaner into a near-empty gas tank then fill up with some quality gasoline in there
 

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everything you mentioned could be a culprit, except bad spark plugs....incomplete combustion would show up as a rich condition due to the excessive amount of fuel left over in the exhaust
I recently learned that this is incorrect. Incomplete combustion like a misfire will show up as a lean condition. The reason is that the oxygen sensor measures the amount of oxygen in the air passing by the sensor. Fuel is in liquid form, albeit vaporized, so the sensor can't see that there is unburnt fuel with a misfire. I was sure that it was just as you thought, but I was wrong.
 

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if your still having trouble with this then check the rubber vacuum tee on the back of the intake manifold on passenger side. i was having the same problem and it looks like the intake actually wore a hole in the rubber tee. big ol vacuum leak. could be a design flaw.
 

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if your still having trouble with this then check the rubber vacuum tee on the back of the intake manifold on passenger side. i was having the same problem and it looks like the intake actually wore a hole in the rubber tee. big ol vacuum leak. could be a design flaw.
This was my issue as well. It's kind of hard to see it. Mine had a pretty large hole in it.

-Rob
 

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Isn't the plastic tee behind bank 1? So wouldn't that show up as Bank 1 lean?
I had the same code and fixing the hole in my plastic tee didn't help, it turned out that on the other side of the manifold (behind bank 2) there is also a rubber vacuum line coming from the tee. The tee is connected to a rubber vacuum hose, which is connected to a hard plastic hose, which is connected to another piece of vacuum hose, which is connected to the back of the intake manifold on the driver's side. Mine had a half inch hole in it, causing P0174. You might want to check the part on the driver's side out.

Tom
 

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I just bought the top parts to a 96 and it had the hole in that same spot. The hole was about the size of a dime. I just replaced the tube there and should be able to throw it on the car.
 

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I just recently had this code (P0174) pop up again in my car. I installed a brand new MAF and fuel filter just the other day. I was wondering exactly where this common vacuum leak is? I'm fairly new to working on my car so I don't really want to just go pulling lines and stuff without knowing what it is. Anyone happen to have a picture or something showing where these particular air lines are?

Also Where are the O2 sensors I need to check? Pics are a plus!
 
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