hello

I am having idle trouble with my truck. it seems related to the IAC idle air control valve. but im not sure if its the valve or the pcm that controls the function of the valve. trouble is that it will idle really high 2500-3000 rpm when started. i found that pulling the plug off the iac valve causes it to drop and die out if not up to temp. but if its up to temp it idles normally. Im not sure how to test if its the pcm causing this or simply the iac valve. i dont want to just start throwing parts at it to find the trouble. is there a reading i can get off the leads from the pcm to the iac ? it is only a 2 wire plug and i dont know where to start to test it . i do have a digital meter to test just not sure what im looking for. as of now im just running it unplugged and i have to baby the throttle for a few min till it warms up a bit other wise it will load up and die ( just like the old carb days when your choke would not engage ). please any help on this would be greatly appreciated.

 

Sounds partly like a problem i had. Pull the codes an check the TPS voltage.

 

sorry i should have mentioned there are no trouble codes and the check engine light never comes on . ( unless the key is in the on position and not started) TPS sensor, guessing thats the Throttle position sensor? and what sort of voltage should i see there? 12v? or a lesser reading ? I also checked all the fuses related to engine management both under the hood and under the dash, all good . I should have mentioned that in my first post. oops lol. Thanks again for any help.

 

Yes, its throttle position sensor, should be around .9v at closed throttle an around 4.0v at full throttle. Detailed explantiion is at oldfuelinjection.com. My CEL wasnt on either. Tps is my best guess going from experience with my truck.

 

hey thank you for your reply. i will look up that site to get more info on how to test it correctly. hopefully that will point to the correct problem with out just throwing parts at it . again thank you for all the help , ill cross my fingers that it wont be too expensive to fix either way. ( currently unemployed )

 

You dont have to change TPS to adjust it to fix idle problems

 

hey thanks for the help 88, it was the tps sensor, i got a better code reader and it hit me with a 122 and 123 code tps volt out of range low and tps out of range high. picked one up a O'reilly's for $60 and all is working right now. again thx for your help , never would have guessed. Also it was kicking a lean o2 sensor code , cuz the tps was not telling the eec-4 to give it more fuel at mid or full throttle. i just learned alot about these MP injection systems. just wish i did not have to pull the throttle body to change it lol. and my tps was NOT adjustable. screw holes were not slotted like some. anyway happy wrenching.

 

The holes in mine werent slotted either, i made it slotted with a small drill bit an trial an error method.