Mazda Meltdown.. Need some help!

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12-09-2009, 09:11 AM

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Fabrik8

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Re: Mazda Meltdown.. Need some help!

Quote:

Originally Posted by ModernDayThorns

The IAC caused it to run at high idle. My mom drove it for a while with it idling really high. Finally it started idling at 4k RPM and they took it in to the shop. They replaced the IAC valve, and a vacuum line that went bad from the heat of the engine due to the high idle.

So the car started running badly one night. Didn't accelerate well and had a bad miss. *Ping* it started running better. The EGR blew the chunk off.

The bad IAC caused the engine to run at high RPM's which raised the temperatures which, caused the Cat on one of the exhaust manifolds to go bad. The bad Cat caused the EGR Valve to blow because the cat was clogged or messed up.

So how could a high idle cause higher temperatures than the engine would normally see during normal load and RPM when not at idle? That doesn't make sense at all. You're saying that the engine is designed to handle full load and RPM, hauling a chunky SUV around town, etc., but doesn't have the cooling capacity for a high idle at zero engine load??????????? That's completely backwards.

I'm sure the issue was the cat converter or whatever, but I think it's completely unrelated to the IACV. A bad cat converter could cause all of the problems listed, and the IACV could be completely unable to regulate the idle of that much exhaust backpressure. So if the IACV is/was bad, it was caused by the much larger problem (the clogged cat) instead of being the cause of the problem.