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misfire and multiple dtc's


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So here's a quick run down of my current issue...... Oh, vehicle is 2000 seville sts with 4.6L northstar

Started having a slight rough idle and reduced gas mileage, so i figured i would change spark plugs to see if it would help. Oil was present in 4 or 5 of the spark plug tubes so i ordered new seals from cadillac. Check engine light came on while waiting for seals and the following codes were present...

P0300 Multiple cyl misfire detected

P0385 Crankshaft Position (CKP) Sensor B Circuit

P0327 Knock sensor Circuit Low Voltage

P1258 Engine Coolant Overtemperature - above 268°F - Protection Mode Active

I replaced the radiator a few weeks back so code P1258 is covered.

The P0300 i figure is from the oil in the tube area

While looking for the CKP sensor i noticed some oil below the intake manifold resting on the plenum. This makes me a little worried..... Where is it coming from? (possibly from valve cover gasket since there some seepage present), and is that why i am getting the other codes? (oil fouling the electrical connections of the sensors?)

If anyone has any knowledge about what might be happening I would greatly appreciate your input!

Thanks in advance!

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If I am not mistaken, 2000 models are known for having bad crankshaft sensors.

P0385 Crankshaft Position (CKP) Sensor B Circuit

If they have not already been replaced, replace both of them.

On the knock sensor code...check and clean wires and connectors.

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There are 2 CKP sensors above the oil filter adapter, which has to be removed to access them. Replace them both.

I'm confused. The "plenum" (on a 2000+ Northstar) is the rubber coupler between the TB and the intake manifold. Are we still talking about the same thing?

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If I am not mistaken, 2000 models are known for having bad crankshaft sensors.

P0385 Crankshaft Position (CKP) Sensor B Circuit

If they have not already been replaced, replace both of them.

On the knock sensor code...check and clean wires and connectors.

Ok, since the code states CKP "circut" do you think it could be excessive oil on the connector fouling the connection? Either way i will order them and replace, just wondering what you think....

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There are 2 CKP sensors above the oil filter adapter, which has to be removed to access them. Replace them both.

I'm confused. The "plenum" (on a 2000+ Northstar) is the rubber coupler between the TB and the intake manifold. Are we still talking about the same thing?

No, i'm talking about the area below the intake manifold. Oil is pooling on top of that, i'm suspecting the valve cover gasket could be the culprit?

I will order and replace the CKP sensors, and dig a little more after work. I have to wait until payday to purchase a FSM so i can follow the correct procedure for the repairs and not foul anything else up. I'd rather be safe than sorry.

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Under the intake manifold is the valley where the starter is. Are you sure it is not P/S fluid. That is right in front of it and has been known to be a source.

Didn't look like P.S. fluid, but i will look a little harder.

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Ok i missed one of the initial codes..... P0151 02 sensor circut low voltage bank 2 sensor 1.

So who knows which bank is one and which is two? and is sensor one the first (pre-cat) or second down the exhaust? I'm really thinking with the codes im gettin that its a conductivity at connector problem due to oil and such......

p0327 knock sensor circut low input

p0385 CKP sensor "B" circut malfunction

p0151 02 sensor circut low voltage

You guys have any other advice or thoughts? I'm not a guru when it comes to figuring out things of this nature......

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