The idle adjustment screw lock nut on my eng.feels smaller than a 10MM, plus the top of the bolt is not a bolt head but round, like a pan head screw. I can't feel any slot in the head or allen head opening. Anyone have any ideas. I bought the truck new so I don't think anyone replaced the bolt, mustave been that way from factory. This thing is hard to reach and can't bee seen easily,even if I loosen the locknut, I see no way to turn the screw to make the adjustment in that confined space.


98 2500 12 valve

 

You might want to check it out with a mirror. It isnt real easy to get to, especially if you have short arms.

 

Sounds like you're referring to the high idle adjustment.
Don't mess with that one, you want the low adjustment.

 

Thanks for the replies. I'm sure I'm on the right adj. bolt. The high idle would be basiclly positioned horizontal in refrence to the pump, the low idle being more or less vertical. I'm on the vertical bolt but am not sure how to adjust it with no bolt head that I can put a wrench on once I loosen the lock nut on the bottom. I was hoping someone else had encountered this delimna and had a solution short of getting a dealer involved. Want to avoid that at all costs, no pun intended.

 

Problem solved. Remarkable what a mirror and drop light will show. Top of bolt was 10mm with a rounded head, to properly contact the linkage arm I suppose. Adjustment went well, thanks for the replies. You can actually see the top of this bolt by looking down between the firewall and the back of the engine with the area properly illuminated. Thanks again for the help.