My car is misfiring. What could be causing this?

2003 CADILLAC CTS
72,000 MILES
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D-BOY
  • MEMBER
  • 1 POST
My '03 Cadillac cts has been misfiring for the past week. I replaced the right/left bank ignition coil, spark plugs & massive air flow sensor and car is still misfiring. Hooked up diagnostic & it shows cylinder 5 misfire.
Oct 21, 2011 at 12:29 AM
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FACTORYJACK
  • CAR REPAIR CONTRIBUTOR
  • 4,159 POSTS
I would focus on #5, check compression, and based on result you may be also looking at a leakdown test. It could be faulty injector, or mechanical problem such as a broken valve spring, or valve itself. Does it misfire under load, or at all times. Under load usually suggests secondary ignition, all the time could be fuel or mechanical. Idle-only misfire could be result of excessive internal leaking(valve face/seat). A leakdown test can confirm this.
Oct 27, 2011 at 2:55 PM
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