Question about 2002 Cadillac Deville

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Intermittent High Idle, Dies on cold starts, bad mileage

I have a 2002 Cadillac DeVille with 131,000 miles on it. It has the 4.6 NorthStar motor and digital dash. Recently, when I pulled in my driveway and put it in "Park" the RPM's raced to like 1800 RPM. I tapped the accelator thinking maybe the choke was stuck or something, and it rev'd even higher to 2300 RPM. After about 30 seconds it slowly came back down to normal RPM's in the 625 range. I shut it off and wrote it off. Today it did the exact same thing to me. Only this time, after I started it again it died. I started it again, it died. AND again only this time I pressed on the accelerator and it started cutting out. Finally it ran ok. It also seems to be getting horrible gas mileage. 12.5 MPG average. Any clue what might be the problem here? Any input would be greatly appreciated.

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  • harleynut102 Feb 01, 2009

    Thanks to dbwest for your input. Greatly appreciated. Brian, I am going to my friends house tomorrow and he has one of those OBD II. I will get the codes and post them tomorrow. The "Service Engine Soon" light is on. I appreciate the help guys. I will get the codes posted early afternoon tomorrow. Have a great evening.

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These cars are notorious for intake manifold leaks. This could also be a throttle position sensor. If you have a MIL (check engine light) I would scan it with an OBD II scanner and pull the relevent code off the scanner it will give us a much more accurate direction to proceed

Posted on Feb 01, 2009

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Check the EGR valve. if the valve gets stuck open the rpms will rev up to prevent the car from stalling. this will happen if the car has been driven on the highway for a extended time on lower mileage cars. sometimes you might also notice that the ac cuts out after long highway  driving when the valve sticks open 

Posted on Feb 01, 2009

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