low idle when in gear

way2fast

Registered User
Here's the problem,when the car is cold it runs at 750 rpms. when it is warm it runs at 500 to 550 rpms. It has a fresh tune-up. The IAC was replaced with no difference. There are no codes stored. It runs great going down the highway. When I place the shifter in reverse [when warm] the motor rpm bogs then comes back to 500 to 550 rpms, the same happens in drive. At a light it doesn't bog it just stays at a low idle. Any Ideas would be greatly appreciated.:confused:
 
you might wanna adjust the RPM IDLE SCREW on the throttle body. Its a ALLEN key. THe size i have no clue. If you open the Screw it raises ur IDLE. If you tighten it it will lower your idle. My idle is at 800 Rpms when warm and in PARK. In Drive it is 600.
 
darkstar_one; I have removed the throttle body but never come across this screw. Could you better describe its location on the unit, or perhaps post pictures?

way2fast; is your car an automatic? In the past, members have had these types of idle problems when the hydralic motor mounts fail. You may also want to check for engine movement, a low oil pan/filter, & look at the mounts to identify them. If they appear stock and you have many miles, there is a very good chance the mounts are bad.
 
low idle

Thanks for the information. I was able to locate the adjustment screw under the rubber cap on top of the throttle body. It took acouple of minutes to think of looking under there. I made a adjustment and the idle is where it should be. thanks again
 
low idle

I'm sorry, I don't know what the motor mounts would have to do with the idle of the engine. Could you please explain ? thanks
 
Re: low idle

way2fast said:
I'm sorry, I don't know what the motor mounts would have to do with the idle of the engine. Could you please explain ? thanks

Way2fast; unfortunately this I can not explain. However, this has been the experience of some other members when they had bad mounts. I believe it mainly applied to automatic transmissions. Perhaps it is related to the knock sensor?

Hopefully another more knowledgeable member in this reguard can add some useful informaton here, I am curious also..
 
When the hydraulic mounts crumble and sag, the limiter arms on the top of the mount rests on the bottom of the retaining bracket. This allows a metal to metal contact from the engine to the subframe. The vibration (evidentally) causes the knock sensor to send a signal to the EEC which then retards the timing and hence the idle drops. At least, thats the story.. It might be intesting to have someone with the problem temporarily disconnect the K sensor and see if it makes any difference.

But don't wait to fix the mounts.. if left broken, the engine will eventually wear a hole in a power steering line and possibly crack the oil pan.
 
I had the very same problem with my sc. I idled realll realllll low when in drive, fine in park about 900rpms. When it was warm the problem got worse and worse, I finally checked on here to see what the hell was wrong and I was told replace motormounts. Replaced with solid mounts, car idles like new.
 
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