Hi:
I have a 1992 F-150 4x4/5.0 E4OD that has been stalling anytime when approaching a stop. It seems to be idling low, and the volts meter is quite low at idle (even with A/C off).
I pulled the codes and got the following:
KOEO: Code 173 (this code is for running I thought, but consistently comes up)
Continuous: None reported
KOER: Code 412 IAC?
Code 632 ( I assume I just didn't do somehting during the test)

So I have the Haynes manual, and followed the porcedure for testing the IAC circuit. Haynes says that with the key on there should be ~10.5 volts there (showing the PCM is sending the correct voltage) and the sensor resistance itself 7-13 ohms.

I couldn't get a good voltage reading with the plug on the sensor so I removed the plug, and it is 12.15 volts with key in "on" position.

I have recently replaced the TPS (fun having to remove the TB to access this) and the oxygen sensor as well. The truck was bought new by my father and he recently gave it to me, and I know he had at one time messed with the throttle stop screw (and it says never do this...doh ).

So my questions are:
a) is the 12.15 voltage reading indicative of a bad PCM??
b) is the 11 ohms close enough to 13 to consider replacing the IAC??
c) if the throttle stop screw is out of factory range, how to get it in factory range again. I remember reading a few ways but there seemed to be some debate regarding whether it should idle with the IAC unplugged or not.


Any help or suggestions would be greatly appreciated!
Also I can't find this site I found recently that had ways of testing various sensors? I thought I linked to it from Steve's code page, but maybe the link is gone? Maybe I'm just crazy and that's not where I stumbled upon this page

Sorry for the long post, just wanted to give all data I have at the time...

thanks in advance
Scott

 

First, clean your IAC with carb cleaner, you can take off the motor and really get in there to clean it too.

Report back here after you have done that. It may solve your problems.

 

Thanks a lot for your quick reply!!

I just went and did that. However I did not remove the motor because it looks like there is a paper gasket and I don't have another to replace it. However I did clean the sensor itself and where it inserts into the motor. Also had the battery disconnected so I cleared the memory as well. The sensor was about 11 ohms before and is now 10.3 ohms after cleaning.

So I went and drove it around for about 15 miles. The check engine light never came on, and it never stalled. Also when stopped the RPM's are a little higher and the volt meter doesn't drop as it did.

I checked codes after the drive and got no KOEO or CONTINUOUS codes, however the KOER codes are the same as before (412, 632).

Should I be alarmed, or just drive it since it didn't stall? Maybe that motor does need to be cleaned out?
Do I need a new gasket for the motor, or make one? It's not hard to remove, just didn't want to get stuck with it off and no gasket.

thanks again Fishin!!!!

 

No problem, You do not need another gasket though. Just unscrew the motor and clean the shaft in the valve body and the socket on the motor then screw it back together tightly, no gasket needed.

Since you know the problem, drive it unless it stalls then you might need a new IAC (~$60).

Good luck, and your welcome. Anytime.

 

If you haven't already, read this thread. It has a link to the full code list.