I replaced the IAC with a Duralast (from autozone because I can return it if it didn't fix the issue). Issue not fixed and IAC is going back. My mechanic was INSISTING it was the IAC, but I don't see how I could possibly have the bad luck of having one that went bad in under a year and then a brand new one being bad outa the box...even if it IS Chinese.

TPS - Everything I've read about it has zero to do with a soaring idle, especially upon starting cold but yet.....
The vehicle IS throwing codes.

The overarching readout states: "ASE cert. Master Techs have seen this issue on your type of vehicle and the most likely solution is: Inspect for Faulty Vacuum Hoses." My error codes read as
P0174 system too Lean (Bank 2)
P1120 Throttle Position Sensor A Out of Range Low (Ratch too low)
P0156 O2 Circuit (Bank2, Sensor 2)

Thoughts?

 

https://www.obd-codes.com/p0156

Shouldn't affect driveability. Sensor 2 only reports on catalyst efficiency.

https://www.engine-codes.com/p1120_ford.html

Fix your TPS..................

Lean code is most likely a vacuum leak or exhaust leak before the upstream O2 sensor.

 

It's just the morning starts that throws the engine into 2800rpm from a cold start. I have a new TPS.... Will let you know how that goes

 

Make certain you reset the PCM so that it is forced to relearn idle control strategy after replacing the IAC.

 

OMG FINNNNNALLY! I replaced the TPS and finnnnnallly it's back to normal. How do I reset the PCM?

 

Disconnect the battery and walk away for a little while (5-10 minutes) is the simplest.

 

Will removing just the + suffice, or do both cables need to be off the terms.?

 

Remove the NEGATIVE cable only.

Do not futz around with the positive cable while the negative is still connected unless you know exactly what you are doing and are prepared for the consequences.

 

Affirmative and Thank you! I have another question for you, but it's a non sequitur, so I think I'll PM you.

 

sent. Plz check your DM

 

Replaced: EGR, IAC (2xs), TPS (2xs), PCV valve and hose.

Idle rises ( horrendously when the A/C is on) upon depression of the clutch. If I were to roll to a stop, it will eventually go down to about 900. Mechanic said TPS was faulty upon running diagnostic/plugging his expensive unit in. Claims the Duralast TPS I bought was **** and that I need to buy a motorcraft one. Since the Dura has a lifetime warranty (a sign that it's crap-ish), I brought it in and got another. Problem seemed solved for a day, but then it came back.

Too, randomly the issue will subside for a 1x acceleration through the gears. Exiting after driving on the highway with a/c on ALWAYS gives the screaming idle which include multiple times of forcing it downward via letting out the clutch.

Is duralast so bad that I could expect one after the other parts to fail? Thoughts on a cause?

 

Truck is v. well taken care of.
Codes: P0174, Sys. Too Lean (Bank 2)
P1120 TPS A out of Range Low (Rach too low)
P0156 02 Circuit (Bank2 Sen. 2)

Could this all be stemming from a bad 02 sensor. P0174 - indicates that Bank2 system is too lean for a pre determined period of time." Perhaps that is occuring under load and it's telling the computer to richen up the mix? I d'no , just reaching.

 

Sensor 2 is downstream, has nothing to do with mixture, it only monitors cat efficiency. A bad upstream sensor should not trip a P0174.

You have a TPS issue. If you have replaced it 2x, you are either getting bad ones or you have a wiring problem. You may have a bad/sticky throttle body.

https://www.engine-codes.com/p1120_ford.html

Theory of operation:

https://www.troublecodes.net/p1codes/p1120/

 

Would you believe I still have this feckin issue? Recap - I've changed the TPS, IAC, MAS, EGR, PCV. I've had multiple mechanics say that 100% there is no vacuum leak. The truck will drive, start and coast with clutch in normally IF I do not turn on the A/C. As soon as that goes on the idle hangs or raises going through the gears. The one weird this is that it could be screamin at 2500+ and as soon as the tires stop moving it'll relieve itself and the idle will start dropping down. This is a constant thing that I can repeat over and over. If I turn the A/C off the issue does not go away. Not until the truck has sat for a few hours/or over night will everything return back to normal. Ideas?

 

You replaced all those items and the rpm problem persists. But, do you still get the codes ?