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Lousy idle, hard miss on cold start

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The motor in my ETC, with 93k miles, has finally started misbehaving.

The idle speed varies a small bit - noticeable only on the tach - by perhaps 50rpm or so. That has been going on for a few months.

But in the last few days, on cold start in the morning, I get a hard miss that clears up in perhaps 20-30 seconds - and then the car runs great, as usual. It feels like an electric, rather than mechanical miss (hooray).

It does start immediately, and gets relatively good gas mileage - 16 in the city, and I'm a fast driver. It does use oil at the rate of about 1 quart per 1000 miles.

Codes are: PCM P0463 history

Any ideas?

The obvious first hit in my mind would be plugs and/or plug wires - but wouldn't this show up as a different code?


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If it hasn't been replaced yet, check the fuel pressure regulator. There's a thread on the forum for checking it, really simple. A new one is $40 from www.rockauto.com.


1996 El Dorado

2006 STS

2000 Corvette

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P0463 - Fuel Level Sensor Circuit High Voltage

That should not cause a misfire though. Misfires that clear up after the engine has warmed up always bother me. Is your coolant level holding steady? Have the plugs & wires been changed?

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