I have a 99 F150 xlt standard cab 4.2L 6 cyl 5 speed manual trans, 206k miles. I have had it around 2 years. After a year i had coolant mixed in the oil so assumed it was head gasket. I Bought a head gasket kit that included all gaskets up from the heads. Changed out everything and ran fine. could of been and intake gasket problem from what i was told afterwards bought whichever it was it fixed the issue. from that experience i took away that i need to find out what the problem is before jumping into it.

My problem now is that after 8 or 9 months of daily driving i am having an idle issue. The temperature here in ohio has dropped a little in the last few weeks(i dont know if that matters). But my truck starts up fine and idles between 8 and 9 hundred, but every 4 seconds surges up around 1,100. It goes back to the middle of 8 and 9 and then 4 seconds later up to over the 1 and back down. This happens in neutral and through 1st , 2nd and so on. if i shift to 3rd and drive a steady pace i can notice the surge still going on every 4 seconds. When i reach a stop light and am sitting in neutral or first, the 4 second surge still continues.

I changed the PVC valve. I a was going to change the IAC but being $65 i didnt want to spend that and it not fix the problem. I put my OBD scanner on it and received the following codes

P0453
P0172

I have heard to clean the IAC and MAF but if those are the culprits id rather spend the money and replace them . I am considered a rookie when it comes to being a mechanic, but if steered in the right direction i can fix the problems. I bought the Haynes repair manual for the truck and was able to do the head gaskets with that. I much prefer this website to the manual as i fell i get better information from "real people with real problems"

Any help would be greatly appriciated. Thank you in advance!!!!

 

http://www.autocodes.com/p0453_1999_ford_f150.html

http://www.autocodes.com/p0172_1999_ford_f150.html

May or may not be related.

 

It's is not the IAC if it operates ok like that. Not stuck closed or open.
The IAC is under the control of the computer.
If something else is happening, the computer can reacts by operating the IAC.
The code 172 is indicating excess fuel lthat may be 'variable' acting the computer detects.
If you have a Scanner and not a Reader, look at the long term fuel trim tables.
You should at least see the table for bank 2 shifted 25%.
This is what sets the code 172.
The table is shifted to 'remove' fuel trying to correct for the excess fuel.
This shift can cause hot stalling and poor low speed drivabiliy and other actions to take place.
The 453 code is a fuel tank system issue that does not pass diagnostics.
Good luck.

 

Bluegrass - P0172 is too rich, not too lean. Air leaks cause a too lean code.

 

Yes, in my hast I got ii wrong.
Just reverse the air/lean to to much fuel/rich.
It works the same but just shifts the tables to other direction.
Thanks for catching my error.

Good luck.

 

P0172 1999 FORD F150 - System Too Rich Bank 1

Possible causes

- Faulty front heated oxygen sensor
- Ignition misfiring
- Faulty fuel injectors
- Exhaust gas leaks
- Incorrect fuel pressure
- Faulty Mass Air Flow (MAF) sensor

Read more: http://www.autocodes.com/p0172_1999_ford_f150.html

P0453 1999 FORD F150 - Fuel Tank Pressure Sensor Circuit High Voltage Detected

Possible causes
- Faulty Fuel Tank Pressure Sensor
- Fuel Tank Pressure Sensor harness is open or shorted
- Fuel Tank Pressure Sensor has poor electrical connection
- Damaged PCM

Read more: http://www.autocodes.com/p0453_1999_ford_f150.html

 

Thank you for the responses. Very informative. You dont get that type of help from no book! Im headed out now to look at everything . Ill post later with the results.