Rough idle after 2 minutes it will come down to 1100rpm?

RWALBROEHL

MEMBER
2006 TOYOTA COROLLA
1.8L
4 CYL
2WD
AUTOMATIC
79,000 MILES

When starting car initial idle is like 1600rpm. After 2 minutes it will come down to 1100rpm.I put it in reverse car seem to run rough. Going forward after warming up and at a light it idles down to 700rpm. Seems to run not as smooth when its was new. My car does not have a throttle cable but is electronic. I can't see this IAC valve that they show on cars with cable control. I did clean the map sensor before and also cleaned the throttle body butterfly on the front side only as I didn't remove it. Is there anything else in that area that need spraying. I used the proper map cleaner and throttle body cleaner. There are no engine codes. So was wondering this design does not have a removable IAC that can be cleaned because I don't see one. Any ideas what to do next. I also changed plugs with new ones. Vacuum lines don't have any cracks. Did a relearn on the idle with key in key off and back on etc. No help.
Thanks
Bob

Sunday, March 1st, 2026 AT 12:30 PM

5 Replies

KEN L

MASTER CERTIFIED MECHANIC
55,440 POSTS

Hi Bob,

Yep this car dos not have an IAC, the throttle body handles all of that. Chances are the throttle body will need to be replaced or you have a sizable vacuum leak. Here is a video for you to help find a vacuum leak, also we should runt he codes to see if any are stored. These two videos will help.

https://www.youtube.com/watch?v=LRKWV4Are5c

and

https://www.youtube.com/watch?v=LBCpCWEFnTg

Please upload a short video in your response of the problem, so I can see what's going on. Ken

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Monday, March 2nd, 2026 AT 9:18 AM

RWALBROEHL

MEMBER
127 POSTS
2006 TOYOTA COROLLA
1.8L
4 CYL
2WD
AUTOMATIC
79,000 MILES

Car seems to have a rough idle and during drive seems to have a minor grinding feel to it. I changed spark plugs with no help and decided to check the engine mounts and found the rear transmission mount looking irregular. Could this be the problem looking at the attached picture

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Friday, March 6th, 2026 AT 9:12 AM (Merged)

KEN L

MASTER CERTIFIED MECHANIC
55,440 POSTS

Yep, you found the problem that engine torque mount is shot and you need a new one, this will make the engine seem rough and make a grinding noise and the engine exhaust will touch the underside of the car. Replace the part and let me know what happens. Thanks for the image it helps. Ken

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Friday, March 6th, 2026 AT 9:14 AM

RWALBROEHL

MEMBER
127 POSTS

I know that back mount is bolted to the chassis underneath. So do you just support the transmission with a jack and disconnect the bolts/nuts after taking the air intake out of the way and have the car on jack stands. I don't want anything falling on me from underneath.
Maybe disconnect the left mount to add in lifting pressure if the back once. Is it possible to do it without a lift?

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Friday, March 6th, 2026 AT 11:08 AM

KEN L

MASTER CERTIFIED MECHANIC
55,440 POSTS

So, the engine is supported by three mounts, front engine, rear transaxle and the torque mount which supports the engine lightly but is there mostly to control the engine roll when in drive or reverse, so I would raise the car on ramps and then support the engine with a jack and block of wood to remove the torque mount, is you run into issues upload a short video or image so I can walk you through the repair. Check out the images (below). Ken

Image (Click to make bigger)