Question, i'm working on a 1998 Ford Expedition and i'm getting the following codes on it:
P0171 - System too lean Bank 1
P0174 - System too lean Bank 2
P1507 - Manf Cntrl Veh Spd Idle Speed Control Auxillary Inputs (Pending)
P0136 - 02 Sensor Circuit Malfunction (Bank 1 Sensor 2)
P0156 - 02 Sensor Circuit Malfunction (Bank 2 Sensor 2)
P1131 - Manufacturer Control Fuel Air Metering (Pending)
P1151 - Manufacturer Control Fuel Air Metering (Pending)
It was running really rough and would not idle on its own, you had to keep feathering the gas to keep it running. If not then it would die as SOON as you let the key go when starting it. I ended up cleaning the MAF Sensor and replacing the Idle Air Control Valve and started it. It now runs on its own and can idle without dieing...although the idle is really low and you can hear it hunting and surging at idle. I re-checked my codes, now i'm only getting the P1131 & P1151. Now that it can idle i went under the hood and can hear a really big vacuum leak, coming from around or behind the throttle body, but cant pinpoint it for sure. can anyone let me know if there is anything in that particular area that is more prone to developing vacuum leaks than the other parts in the pic? Wherever its coming from its a pretty big leak, you can really hear it, sounds like someone blowing really hard through a straw...thanks.

 

Follow the PCV line where it goes around behind the intake manifold and feel back there for the rubber elbow. It will prolly be soft, mushy, colapsed, and have a hole in it.

 

Cool thanks. I read up on it some more and seems to be a really big issue. I'll check it tomorrow and hopefully that'll be it! Thanks again!

 

I cant find the PCV hose for crap, can someone point it out for me?

 

Nevermind i found it...but this one doesnt T off liek the pics say....any ideas why?

 

You can spray WD-40 around where you think the air leak is. If the idle picks up while spraying any particular area, you've found where the leak is.

 

Yea I found it...the pcv boot was completely broken in half...the hose was just hanging there, not even close to the boot. I replaced it and started it up...ran like a champ. Drive it for a while and it didn't throw any codes. Idles like a charm! Thank all of you for your help!

 

Here's a pic of the old boot on the top and the new boot on the bottom...you can see that mug tore completely off!