High RPM idle in park after changing intake manifold gaskets that were causing a rough idle. The rough idle is gone but not the car idles in park at 1500-1700 rpm. In gear everything is fine.

Check the vacuum hoses, and the intake manifold gasket for a leak.

This code indicates a large vacuum leak. You can sometimes find a leaky gasket by spraying ether on the gaskets while the engine idles. If the engine changes speed while the gasket is sprayed, you have found the leak.

This is a typical vacuum leak. Check all the hoses. If none are sucking air then use WD40 and spray around the intake manifold. If the engine runs better or changes how it runs then look at replacing the intake manifold gasket.

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.

the intake manifold gasket at the #1 cylinder shifts over and causes a vacum leak which causes a high idle and sometimes a p0157 code with the ses light,,,,you will need to replace that gasket like a $500job,fairly involved,,,,with the car running spray water DIRECTLY at the #1 intake port area the one closest to the belt and see if it runs rough,,,,

Check all the old hoses or vacuum lines leading to the manifold...i found a small crack in one of my lines that was causing me a rough idle..of course it was way in the back were i could hardly see it...use an inspection mirror and take your time. also a plugged cooling sensor lie leading to the throttle body could possibly cause this problem too..it senses the temperature and regulates the idle circuitry.

CHECK FOR A LEAKING INTAKE MANIFOLD GASKET, USE A CAN OF CARB SPRAY AND SPRAY AROUND THE TOP OF THE ENGINE, IF U HIT ON A LEAK U WILL HEAR THE ENG CHANGE TONE AND IDLE RPM.

Vacuum leaks. Check all hoses and intake bolts. Leaking EGR or plugged PCV valve. Air filter plugged. Leaking head gasket. Worn timing chain. Camshaft lobes worn. Valves burned or leaking. Fuel idle control system or sensor. Good luck!

hi,seem you have leak on intake manifold or rubber seal on injector nozzle,be careful drop a little amount on kerosene on intake manifold and nozzle,observe if your idling get high the is there,maybe renew rubber seal on intake gasket,ty

sounds like a fuel delivery problem. try cleaning carb.