help please with issues

[mycool]

I have a 1999 XLT 4.0 OHV. I threw a code the other day for the IAC so replaced the MAF since IAC is built with that. Still idling like garbage. can sometimes floor the gas and it will hardly move. thinking maybe it is TPS but is only every now and again. also hearing a slight knocking sound when turning the truck in forward and reverse. i thought at first maybe my tires were rubbing and to no avail it isn't so possibly a cv? not sure really open to suggestions. sometimes when i start the truck it just idles surging between 600 and 300 rpms. turn it off then goes to 1k until in drive then back to 750 not sure why just shutting it off and tryin it again makes it work better. changed fuel filter not long ago. no way to read pressure on fuel rail.... always throws p0171 and p0174 bank 1 and 2 too lean... and my gas guage just started acting up.... isn't reading correctly... goes to way past full til i hit a certain level in the tank then drops appropriately. PLEASE HELP i know this is a lot of different issues but I need all the help i can get. don't want to be raped by a shop so would love a few tips. still throwing p0171 and p0174 and think it was a problem long before i got the truck as someone removed the check engine light in the guage (doesn't light up so that's my guess) thanks all in advance:exp:

 

[rwenzing]

The IAC (Idle Air Control) valve is not part of the MAF assembly. You're thinking of the IAT (Intake Air Temperature) sensor - it is part of the MAF assembly on some engines. What "IAC" code did you have?

For the lean codes, the first things to look for are vacuum leaks (air leaking in between the throttle body and combustion chamber) and other unmetered air leaks (air leaking in between the MAF and the throttle body).

 

[mycool]

iac code high circuit input. i think that was the code. reset the computer and it was cleared. i will check for vaccum also thanks so far.

 

[aldive]

Have you cleaned or replaced the IAC?