I have a 2000 f150 and i have been having a lot of trouble with my idle. When my truck is cold it will idle very rough at about 300rmp and sometimes die. I had the codes 171 and 174 which are both banks running too lean.

Things i have replaced-IAC, spark plugs, catalytic converters
also i cleaned out my MAF sensor

I believe it is a bad vacuum hose but cannot find the source.

If you have any suggestions please let me know ASAP!

 

Why are you starting a new thread for the same trouble?
Go back to your origianl thread to keep continiuity.
At this point you need to have it looked at with a scanner to see live data and detect what is not happening.
Replacing parts is not going to do it, trying to get lucky.
The cold start sequence is complex.
A fault in any one of a number of areas will cause the issue.
I think I explained how it works before, so you have to get deeper into it to find what is not working correctly.
I think I told you the low cold idle and lean codes don't go togather as a singular trouble.
One is not enough air the other is to much air.
Have you looked at the signal voltage 'too and from' the IAC after you replaced it and found it did not help? Maybe it's not being controlled by the PCM and could be one reason for the low idle. Possibly a harness problem.
Ignoring what I am explaining to you won't get you very far by keeping asking over and over again.
Sorry to sound harsh but we can't help you very much more.
There have been a rash of calls for help that are ignoring help offered, so I am beginning to not respond to them any longer if the person is not going to listen and do the work based on some min of understanding of how things work and look at it from that point of view so they can recognize the faulty part..
Good luck.

 

You started with the low idle and problems, but eventually said you had those two codes. The 171 and 174 are lean codes and "normally" the first place to look is the small vacuum hoses on the motor. One common place for failure on the 5.4 is above the driver side valve cover. There are two small hoses 3/16 and 1/4 inch that connect to the EGR system. They are about 8 inches long and will get hot and brittle on the bottom end. Pull all hoses off one at a time and check every hose for brittle / cracks. ---- AS bluegrass said, there are other things that could also account for the problems, but hoses checking is simple and cheap.