Strange idling, finding codes.

[josh_m]

So my 1989 2.9L ranger idles very strangely. Between shifts rpms will stay up, and eventually drop down. If i rev the truck in neutral, rpms will stay up, then drop down. Now can i use codes to see whats causing the problem (IAC or TPS im assuming).

How do i get codes ? Its an OBD 1 truck so im assuming something to do with the CEL. Truck does not show a CEL when driving however. Also, is there an online "code book" anywhere ? Thanks TRS

 

[dgndngrngr]

ya you can use a code reader or a voltmeter:
http://www.therangerstation.com/tech_library/OBD_I.html

and here are the codes:
http://www.therangerstation.com/tech_library/2digitcodes.html

when you get the codes post em on here and we'll help you out

 

[IMenriched]

So my 1989 2.9L ranger idles very strangely. Between shifts rpms will stay up, and eventually drop down. If i rev the truck in neutral, rpms will stay up, then drop down. Now can i use codes to see whats causing the problem (IAC or TPS im assuming).

How do i get codes ? Its an OBD 1 truck so im assuming something to do with the CEL. Truck does not show a CEL when driving however. Also, is there an online "code book" anywhere ? Thanks TRS

there is a list of code in the tech library here as well as how to get them read. if you get/borrow a chilton repair manual they are in there too.

getting codes is agood place to start

when was the last tune up?? you might have a broken return sping on the TPS..or a fraying throttle cable.

check the back side of the throttle plate for carbon build up

could be a vacuum leak too