: 2002 Deville misfire on Northstar

04-08-14, 11:04 PM
Just bought my first cadillac deville, it's got over 300 kms on it. Scanned engine codes and came up misfire on all cylinders but cyl number 6 is most common misfire. Any suggestions on how to diagnose the problem ona tight budget? Please email me at brent_macleod16@hotmail.com thnkyou for your time.

04-08-14, 11:08 PM
What are your codes? P300 and P306? Or all misfire codes present?

04-09-14, 10:15 AM
Start with a good TB cleaning.

04-09-14, 06:53 PM
The code coming up is p0306, the information replaced all the plugs yesterday and now it's just missing on cylinder 6. What is the firing order for this model


She's got alot ok KM on it, 313000 km, I really hope I don't have to put a rebuild kit in it. So any suggestions to get it to run right I would be really greatful!!! Thankyou.

04-09-14, 07:04 PM
Disregard the pre-2000 coil arrangement ........... the rest is all Northstars

What plugs did you use, and did you check the coil connector boots for tracking and the cassette coil towers for cracks ?

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04-09-14, 09:08 PM
Firing order is irrelevant on this engine. Nothing you can to to it, with it or about it.

If you changed the plugs and cleaned the TB and still have a misfire, you might check the #6 plug boot for any signs of carbon tracking. If you find none, then chances are you have a bad coil and will need a new ignition cassette.

Is it safe to assume you used A/C Delco 41-987 plugs?