Hey guys I was wondering I have a 92 f 150 extended cab long bed 4x4 with a 302 5 speed.....well it idles up and down sometimes then sometimes it doesn't want to idle at all or high idle......then sometimes it's perfect.......any ideas.....

 

First thing is to Check for Stored codes. It's as simple as using a paperclip and counting the flashes.

Do a search on here or Google and there is a plethora of information on how to and I'm sure video's.

Your wallet will thank you before throwing any parts at it.

 

Check for vacuum leaks and check the TPS voltage.
Should be less than 1volt.
Also see if your IAC needs to be cleaned out.

 

i read the codes today and got this ......21.....24...29....33....67.......what would be going on here .......

 

Codes 21,24 indicate the truck was not fully warmed up before running the Key On Engine Off (KOEO) tests.

Code 21: ECT out of self test range 0.3 to 3.7 volts.
Code 24: ACT sensor out of self test range 0.3 to 3.7 volts.


Code 67 (KOEO): A/C ON during the KOEO tests.

Stored Codes (CM)
Code 29: Insufficient input from vehicle speed sensor.

Indicates the VSS signal has been low at some point during operation.


Code 33 (CM): EGR valve opening not detected.

Indicates the EGR feedback has not changed when the EGR was commanded open by the computer at some point during operation.

 

ok I did the test with the engine cold......and the speedometer doesent work would that be the vss ......now what would cause the get to not open and would that cause it to idle weird.....it goes up sometimes down then sometimes it runs perfect......

 

It's possible a faulty VSS input could influence the PCM to change the pulse width duty cycle to the IAC, but not when the vehicle is at rest. A sticking or faulty IAC can also cause idle issues.

A rolling idle can also be caused by a faulty TPS (even though it may not flag a code), worn throttlebody or worn throttlebody blade shaft bushings as well as previously mentioned vacuum leaks.