Rough Idle In My Car – Do This

rough ilde engine problemsReader Question

Hi Austin, We have a Toyota Camry, 4 cylinder, automatic transmission. The other day when my wife parked it at a friends house, it would start fine but would not idle at all once you took your foot off the gas pedal to apply the brake and move the shift lever.

I drove to pick her up expecting to have it towed. I decided to see if I could keep it running and still get it into gear so we could get it to our mechanic without a tow. I pressed the brake with my left foot while keeping the engine running with my right and was able to get it into gear and moving. After that it started to idle fine and has been starting up and running perfectly since.

Do you know what may have caused that so we can prevent it from occurring again? Pretty scary for my wife who has to park at out of the way places with her job sometimes. A friend that owns a body shop says that the same thing happens when they have a car with a run down battery but our battery
appears to be fully charged.




Hey there Tony

If you came to my shop I would check two things.

First, Inspect and clean your Throttle Body. The throttle body is basically where the carburetor used to be on older cars. The fresh air intake duct from the air cleaner box attaches to the throttle body, and if you remove the fresh air duct you will see a metal vain just inside. This vain opens and closes as you push on the gas pedal allowing more or less fresh air to enter the engine.

Over time this vain will become dirty/gunky and will stick causing dying at idle problems, slow to start problems and rough or erratic idle speed problems. You can take a rag and a toothbrush with some intake cleaner spray found at your local auto parts store and clean the throttle body and the vain (the large valve you see at the front of the throttle body) of dirt.

This simple procedure should be done periodically as part of general maintenance anyway and can usually be performed by any mechanic or fast lube place. Not only does it help with idle issues, but can help with faster starts too.

Watch my video of me cleaning a throttle body, which is basically the same as on your car too.

Second, I would also make sure you do not have a vacuum leak somewhere under the hood. With the engine running and the hood up listen for a hissing vacuum leak noise under the hood. I have seen that fresh air duct hose I mentioned get a small hole in it on the underside of the hose where it is not visible.

This crack in the hose will cause a vacuum leak and will cause the engine to die. Run your hands under the hose (or remove the hose if you feel capable) and inspect for a vacuum leak or crack.

Here is a simple but effective way to easily test to see if you have a vacuum leak somewhere under the hood.

Here is another one, simple but it works well for shade tree mechanics at home.

Keep me posted will ya?

Austin Davis, The Honest Mechanic

Austin Davis,
The honest Mechanic


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