2002 Jeep Liberty missfire on cylinder 3

2002 JEEP LIBERTY
120,000 MILES • 6 CYL • 4WD • AUTOMATIC
Avatar
AARONJ09
  • MEMBER
  • 1 POST
reading code p0303 witch is missfire on cyl 3. changed all spark plugs,checked coil pack (getting good spark) and changed fuel injector. but still getting same code.
Nov 29, 2009 at 10:07 AM
Advertisement
Avatar
KASEKENNY
  • CAR REPAIR CONTRIBUTOR
  • 18,907 POSTS
A misfire can be caused by a number of things but we need to check and make sure you are getting spark on the plug. I would remove the plug and hold it against the block and crank the engine just to make sure you have spark.

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

If you do then we need to check the compression on this cylinder to make sure we don't have a larger issue.

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

You need to have a minimum of 100 PSI as I attached the spec below. However, if you have 100 PSI and the other 5 cylinders are around 150, which is about normal for this engine, then we still have an issue even though it is above the minimum spec.

Please run through this and let us know what you find. Thanks
Image (Click to enlarge)
Attached Media
Nov 10, 2021 at 7:39 AM
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.