i have a stepper motor fault code, i cleared it a couple days ago after finding the vac hose to it was broke, i figured that was obviously the problem. it came back so im going to clean it but i was wondering what exactly is the function of it, something about the idle right. also when i crank the truck up the idle raises to about 2500 rpm then drops slowly is that related or normal or something different all together. i just bought the truck and i'm trying to go through and work out the little things as well as do all the maintance items. its a 94 w/140,000 miles. i've done air and fuel filters, oil change, plugs and wires, belt, radiator flush and induction cleaning. soon atf fluid, diffs, transfer case, and grease all the fittings. any help or suggestions of things i should look into are appreciated. thanks.

 

The stepper motor controls how much air goes into the engine when at idle.
Take it out and clean it with out moving the plunger, also clean the port that it goes into.
That idle at start up is high, it will jump up straight away when you start it but then it should go back to normal really fast.
Normal hot idle is 600rpm, cold idle is closer to 1,000 rpm.
Make sure that you also set your ignition timing correctly and check your vacuum advance and replace your cap and rotor.

 

not that big of a deal, but hot idle should be 720. It is in Rave.

 

the cap and rotor look pretty good, thats why i haven't touched them, but the vacume advance are you saying just to make sure it works or that, that could affect the idle? it seems to idle alright but every once in a while it idles a little rough thats what i think triggered the light, i guess that was the stepper malfunctioning.

 

I would suggest cleaning your stepper first. As for the cap and rotor, be careful with the rotor, or you will have to replace your distributor.

Check your vacuum advance hose for cracks.

 

do you think a vac leak could make the idle linger high at startup? it doesn't seem like its going too high just that it seems like it sould go down quicker, maybe i exagerated a little with 2500rpm maybe 2000 or so.

 

no, the rest of the list is just for things to check while you are in there.

Clean your stepper first.

 

hey i cleaned the stepper and reset the code. it lasted about a week then came back on, pulled it out it was clean, is there something else that will trip that code or an electrical test i can do?

 

motor may be failing. It is an electric motor that "steps" to certain levels. It doesn't just turn, it goes in preset increments allowing a certain amount of air into the intake. The higher the idle, the more it steps open, just like the butterfly on you throttle. If cleaning didn't fix it, and you are still getting a high idle, it isn't responding fast enough. At 140K, it has done its job. Replace it.

 

If you replace it, rumor has it this should work for you:
http://www.ryderfleetproducts.com/cg...uct_detail.jsp
$31
I've never tried it myself.