Question about Toyota Corolla

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Hi I drive a 2006 corrolla with 70,000 miles. I noticed the idle slowly but surely gettin a litttle rough and lower. This only starts to happen after I have been driving for about 5 min. It usually happens when I am at a red light in drive. the idle will fluctuate in a low range about 400-500 rpm also accompanied by a slight vibration caused by the low idle. nothing serious though. I have already got the throttle body and fule systems cean by the Dealership. is there anything else i can do? do i have to adjust the throttle? the dealer didnt recommend anything so I feel there is nothing wrong. Maybe it just happens as the car ages.

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It's been almost 2 years since you posted the question so it's likely you will not see my answer to your question.

First, do NOT make any adjustments to your throttle body idle setting. The screw most likely never budged since 2006 so you should not touch it since this is not the root cause. But yes it is wise to check all vacuum lines as "craig" suggested.

I have a 2007 Corolla CE, 1.8 liter VVT engine, 5 speed manual transmission which I bought new from the dealer. Currently has about 108k miles on it. After about 4 or 5 years in cool to cold weather it started doing the same thing. I researched it online then asked my local Advance Auto Parts person who confirmed my hunch. It is known as "idle hunting" when the engine is cold, in colder outside temperatures the idle rpm's will increase up to roughly 2000 rpm then drop to idle, then back to 2000 rpm, then repeats multiple times. Then after driving a short distance, stopping and running at idle, the idle speed may drop to 600 or 500 or as low as 400 rpm, running quite roughly but still keeps running. My Corolla normally idles smoothly and steadily at 800 rpm when warm or hot. The idle hunting or low idle rpm will typically correct itself when the engine warms up enough.

The problem: the intake manifold gasket has aged and shrunk a bit, allowing engine compartment air to get pulled directly past the gasket and into the cylinder head intake port. This causes an imbalance between the reduced air filter airflow sensed by the Mass AirFlow (MAF) sensor versus the actual air/fuel ratio versus the engine rpm versus the oxygen level in the exhaust stream. The gasket will shrink more as the temperature under the hood drops, allowing more air to flow past the gasket. The Engine Control Unit (ECU) is simply trying to do its job as programmed by increasing fuel delivery to compensate for the overall imbalance, then when rpm's get too high it will reduce fuel delivery.

The solution: purchase a new intake manifold gasket for roughly $10 to replace the stock gasket. Mine is a thin orange polymer gasket with round cross-section which seals around all 4 intake ports. You can search for instructional video of how to install it on YouTube.

I purchased one but did not install it yet. I am sure this will resolve the problem since all other suggested fixes I found on the internet did nothing but unnecessarily frustrate the owners.

Posted on Jan 05, 2013

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Hello friends I have the same problem on my corolla 2006 with 106,000 miles and everything began when remplaze battery and done everything nothing to solve the problem, and cleaned the throttle body, changed the intake gasket, changed the maf sensor and all the small vibration when standing and when braking also, earlier in my house had a 2004 and so my mother decided to sell it and with this I'm thinking the same thing, the last thing I have to do is change the spark plug to see if it improves a little, is that the car makes when standing as far off but that's because the rpm drop too 600 650 and vibrates so I would recommend something else, no power check thanks

Posted on Feb 01, 2013

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Check on your throttle body and see if there is a adj screw for the idle and set it a little higher. should idle at 700 rpm. also check all vacuum lines for leaks and cracks at connections.

Posted on Apr 03, 2011

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