idle erratic
Thread Starter
4th Gear
Joined: May 2008
Posts: 4
Likes: 0
idle erratic
i recently replaced the IAC and TPS on my 1986 L98 to resolve a throttle hesitation. It kinda resolved that issue, but now when the car gets to normal operating temperature the idle increases to 12-1500 and stays there until i place the car in neutral and hit the accellerator. Then it drops back to 6-700 where it should be. Did i goof up replacing one of these components. The TPS was installed like for like although it can be rotated slightly i tried my best to line it up where the old one was situated. The IAC instructions only stated after installing right out of the box with no adjustments needed. Was to start the engine for 5 seconds shut off, wait another 10 seconds then restart. Maybe that sequence was for the PCM to relearn. Any suggestion to my increased idle how to remedy? Thanks in advance. Howie
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
The fact that you can "kick" the idle speed down, indicates that the IAC has become acclimated. I agree there is something holding up the throttle from closing as it should. Since it is a new problem, I suspect the new TPS. You may not have properly engaged the tang of the TPS with the throttle shaft of the TB. You say, referring to the TPS, "it can be rotated slightly". If you have the correct TPS it should be able to be rotated quite a bit. With that rotation, you need to set the TPS voltage. If all else is OK, including the throttle cable, as combustables pointed out, the throttle shaft bores in the TBs are likely worn. From your post, however, my money is on the TPS.
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