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03 Matrix Cold Start Revving

On cold mornings when I start my car the engine revs sporadically. It will initially stay at about 1200 rpm for a couple seconds, but then the rpms slowly increase or surge until cut off about 2400 rpm and the process starts again until the car is warm. The colder it gets the worse it is, usually 50 degrees or less it’s noticeable. It has done this since I have owned it with 40,000 miles (now has 117,000). I did find this TSB EG022-07 but it is for a manual transmission, but describes my symptoms (mine is AT). Also, I believe the ECU was replaced with the catalytic converter on another TSB at 78,000 miles in 2009, which is 2 years after the TSB. Is it possible that the ECU still needs an update? Or, is there a different problem? I know its not the o2 sensor, plugs, battery, or intake gasket, and of course Toyota mechanics told me its normal, and cant duplicate the problem.

Idle rpms at 2400 isn’t normal in any car I’ve ever experienced. It seems there is definitely something wrong. There’s a bunch of things – including vacuum and fuel system problems – that could cause it. My first suspicion though would be the idle air control valve is sticking in cold weather. It’s a pretty common thing to be the cause of this kind of problem. Has that gadget been checked or replaced yet?


My 2005 Camry idles high for a few minutes until it’s warmed up

And I know for a fact there’s nothing wrong with my car

I did some looking around and found this is a common problem on the Corolla and Matrix which use the same engine. The fix is to replace the intake manifold gasket.

I did replace this gasket, but I will check to be sure it is the orange updated gasket. Db4690, every other car I have owned warms up about 1200-1400 rpms. This is much higher, unsteady, and not normal. Our 93 camry never did this when we owned it, and our 03 4runner doesn’t do this. The IAC valve I was considering replacing.

Before my Corolla’s IAC went on the fritz it idled considerably higher when cold than warm, then came back down to normal of 700-800 within 3-5 minutes, but I don’t think it ever idled at 2500 no matter how cold it was. I admit I never measured the cold idle speed, but by the engine sound I’d estimate maybe twice as fast as warm idle, 1500 rpm max.