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2000 deville (152k) runs as if plugs are filing up


jamesc

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That is a misfire code. Check routing of your wires, check for vacuum leaks, check your coils to be sure they are firing.

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Check for a ripped plenum. On the 2000+ Northstars, the plenum is the rubber coupler between the TB and the manifold. They tend to split on the bottom where it cannot be seen and causes a vacuum leak. Spray some Brakleen or carb cleaner around the base and listen for an RPM increase.

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Check for a ripped plenum. On the 2000+ Northstars, the plenum is the rubber coupler between the TB and the manifold. They tend to split on the bottom where it cannot be seen and causes a vacuum leak. Spray some Brakleen or carb cleaner around the base and listen for an RPM increase.

Thanks Ranger, I will do that. I recall having it replaced somewhere around 75K or so. That may be it, i will let you know. Have a great day.

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Ranger, not to dispute you, but in the past when that rubber plenum goes bad it creates a lean mixture and the following codes show up because of the unmetered air rushing in behind the TB.

P0171 - Fuel Trim System Lean Bank 1

P0174 - Fuel Trim System Lean Bank 2

I was getting a P0300 when I did the upper intake manifolds in an 02 3.1 Chevy, but I did something wrong putting the intake manifold gasket in and it created a misfire on one or two cylinders possibly adjacent cylinders. I am leaning toward cracked porcelon on a plug, incorrect ignition wire routing, a bad coil or an injector problem.

I would do a compression test on the engine first

Test the coils for even strong output

If those check out, I would look toward the injectors testing their resistance and listening to them with a scope to hear them working

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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I agree on the lean codes Mike. I mentioned it because it is common and easy to test. Seems I have heard of it causing a rough idle, but not positive.

Understood, thanks

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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A leaking boot should create lean code. All the boots will go bad sooner or latter.

One bummer on the Cadillacs is you will only get a po300. The system will not identify which cylinder has the miss fire.

No spark plug wires on the 2000. Just coil banks. I suspect a bad coil bank.

Kinda like the old GM HEI modules. Those who knew always carried a spare.

I carry a spare coil bank in the trunk.

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