Idle speed jumped up.

[LT4John]

For some reason, my 96 LT4 is now idling around 1000 to 1200 RPM. Before two days ago the idle was constant around 500, and sometime the car even stalled before it warmed up. Now when the engine is cold it runs at 1200 RPM and may only go down to 1000 when warm. Also, I have noted that I now hear the engine whine though the radio, I don’t know if they are related.

Tomorrow after work, I am going to check all my connections around the throttle body, remove the MAF sensor and clean out the inside of the throttle body.
Is there anything else I should be looking for?:confused

Thanks in advance for any help.

 

[sumoboy]

It could be your IAC but I would check for vacuum leaks first and if you do clean your throttle body be careful on what you use, they make specific cleaners for them.

 

[superhorse]

high idle

hi there lt4 john , I have the the same problem with my 95 lt1. I cant figure it out. cleaned tb, replaced iac, checked all lines. the only other prob. is the cruise cont. does'nt work ..maybe related... vacume possibly..... dont know. does your car take a long time to idle down to 1,000? my car idles at 900 to 1000. let me know if you fix it what you did.....thanks rob

 

[LT4John]

Superhorse,

I am not sure why, but the idle dropped back down to normal. But now I have a "Service Engine Soon" light. I shorted the OBDII connector (pins 4 &12) and only got back a C12 code, which says I don't have any stored codes. Can't figure it out, but I will let you know when and if I do.

Thanks for your help