My 04 Seville had several codes.

RJOTWINS

MEMBER
2004 CADILLAC SLS
88,000 MILES

I've fixed several of the codes. I had a new tune up, o2 sensors, grumet. I still have p300 code and my car bogs down alot, plus it shakes at 500 rpms. It cuts off at times and I have to put it in neautral. My mechanic says I need crankshaft sensors. So what can I do?

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,645 POSTS

A PO300 is a random misfire. Many things can cause it. Start easy. Check for vacuum leaks, and check fuel pump pressure to make sure it is within spec.

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Monday, November 14th, 2011 AT 11:25 PM

CADIEMAN

MECHANIC
3,544 POSTS

If you have the engine scoped they will tell what cylinder is causing the misfire. It may be a bad plug or wire.

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Tuesday, November 15th, 2011 AT 3:48 PM

RASMATAZ

MECHANIC
75,992 POSTS

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

1.Defective spark plugs

2.Inadequate spark/coil,defective spark plug wire.

3.Lack of compression

4.False air leakage.

5.Faulty fuel injectors.

6.Insufficient fuel pressure.

7.Contaminated fuel.

8.EGR valve that is leaking.

9.Oxygen sensors.

10.Throttle position sensor.

11.Manifold absolute pressure sensor

12.Mass Airflow Sensor

13.Idle air control valve

Note: If it doesn't apply disregard it-

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Tuesday, November 15th, 2011 AT 3:55 PM