Has a misfire, check engine light on and code PO306

BRENDA LARGE

MEMBER
2003 DODGE DAKOTA
3.9L
V6
4WD
AUTOMATIC
226,000 MILES

Skip’s has a misfire. Mechanic I took it to said I need a new motor. I don’t think I do. Has to be something you can fix when it doesn’t skip, it runs fine, uses no or uses no water, gets great gas mileage. But now has that code and I skip.

Wednesday, December 9th, 2020 AT 3:30 PM

1 Reply

JACOBANDNICKOLAS

MECHANIC
109,755 POSTS

Hi,

The 3.9L is a very durable engine if maintained. So, it may be something simple. Have you done the basics such as a tune-up (spark plugs, wires, distributor cap, and so on)?

Also, is there any noise associated with the misfire? For example, is there a ticking or knocking from the engine?

If you have already tried a basic tune up, then the next thing I would suggest is to see if compression is within spec specifically on cylinder 6. Here is a link that shows how it's done:

https://www.2carpros.com/articles/how-to-test-engine-compression

Here are the directions specific to your vehicle:

________________________________

2003 Dodge or Ram Truck Dakota 4WD V6-3.9L VIN X
Cylinder Compression Pressure Test
Vehicle Engine, Cooling and Exhaust Engine Testing and Inspection Symptom Related Diagnostic Procedures Non-Trouble Code Procedures Cylinder Compression Pressure Test
CYLINDER COMPRESSION PRESSURE TEST
TESTING-CYLINDER COMPRESSION PRESSURE
The results of a cylinder compression pressure test can be utilized to diagnose several engine malfunctions.
Ensure the battery is completely charged and the engine starter motor is in good operating condition. Otherwise, the indicated compression pressures may not be valid for diagnosis purposes.
1. Clean the spark plug recesses with compressed air.
2. Remove the spark plugs.
3. Secure the throttle in the wide-open position.
4. Disconnect the ignition coil.
5. Insert a compression pressure gauge and rotate the engine with the engine starter motor for three revolutions.
6. Record the compression pressure on the third revolution. Continue the test for the remaining cylinders.
Refer to SPECIFICATIONS for the correct engine compression pressures.

See pic 1 for compression specifications.

_________________

If you decide to check compression, let me know the results before you put it together. I may ask you to try an additional step.

Let me know. Also, let me know if the light is always on, what seems to cause the misfire, when it seems to happen, and anything you can think of that may help me. Additionally, let me know if there is any noise (ticking or clicking) coming from the front of the engine. The timing chain could even be stretched and worn.

Take care,
Joe

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