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Ron, ASE Certified Technician
Category: Cadillac
Satisfied Customers: 35857
Experience:  34 year as an ASE Tech
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I have a 09 DTS, Started it up yesterday, idel was a bit

Customer Question

I have a 09 DTS, Started it up yesterday, idel was a bit rough and check ingine light came on? My mechanic checked, cyl. # ***** was misfiring (Igniter??) He chechked Compression, and it was 90LBS?? 118K Miles, always serviced, driven easy?? Says he needs to pull the head???
Submitted: 2 years ago.
Category: Cadillac
Expert:  Ron replied 2 years ago.
Hello, my name is ***** ***** I am a professional here at Just Answer. I have noticed that your question was not getting a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.
If you are only getting 90 PSI of compression on the misfiring cylinder then its not going to fire, you need at least 100 to 130 PSI in order for the cylinder to fire properly.Unfortunately your Mechanic is correct, the head will need to come off and your likely looking at a burned valve and or bad valve seat.