Dr Jekyll

Hello all, I have seen a few threads on this forum about the L98 idle problem but I don't see much follow up on a resolution tho. So here is how I managed to correct my looping L98. After some research and browsing around this great source of knowledge. I decided to start with the IACV. I was going to pull the throttle body and clean it anyway so why not begin with this easy install two birds one stone. I should also mention I did a full tune up 1st OEM plugs-wires-cap-rotor-coil along with a new air cleaner and PVC valve replaced some other random plastic vacuum lines that looked shady. I plan on replacing all the plastic with new rubber and Ts but that's another day. So anyway I pull the throttle body (disconnect the battery 1st) break a few plastic vacuum lines in the process of course and replace the IACV after a good couple cans of throttle body cleaner a tooth brush and clean rags it was ready to reinstall. I also noticed my mounting gasket was cracked in the middle allowing the two ports to bleed into each other. Probably not a big deal but replaced the mounting gasket as planned anyway. All buttoned back up checked and double checked everything was hooked back up correctly I fired her up. I notice immediately my idle was high but smooth. I figure the increase is probably due to the now squeaky clean throttle body so I let it warm up and sure enough the idle drops down to 750 in park and 580ish in drive. I take it for a nice long drive being sure to hit all zones of the throttle from granny slow to WOT. Great throttle response and no more looping/surging idle. I did notice my set screw on the drivers side of the throttle body was missing its plug so apparently someone has adjustd her. I have not touched this setting as everything I read says DON'T. Does anyone know a source out there that has the correct setting for this screw IE: 2 1/4 turns from 0. I'm not playing with it until I have a start point to put it back to factory settings or ad least make sure it was never put out of factory settings. I hope this helps anyone out there with the same issue. The IACV is a likely culprit and a good starting point and while your in there give the throttle body a good douching she probably needs it.

JackDidley

I set my idle screw by watching the IAC counts in Datamaster. With the timing correct, I try to get the IAC at 30 counts and the TPS at .52 at idle. Tweaking the idle screw about 1/4 turn at a time, in or out to get 30 and then setting the TPS.