How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Dave Nova Your Own Question
Dave Nova
Dave Nova, Cadillac Technician
Category: Cadillac
Satisfied Customers: 19450
Experience:  ASE Master Certification. GM World Class Certification
11042942
Type Your Cadillac Question Here...
Dave Nova is online now
A new question is answered every 9 seconds

HAVE A 2003 CADILLAC DEVILLE, P0300 CODE IS UP. I REPLACED

Customer Question

HAVE A 2003 CADILLAC DEVILLE, P0300 CODE IS UP. I REPLACED PLUGS AND WIRES FRONT AND BACK AND IT IS STILL MISFIREING, I HAVE A SNAP-ON SCANNER HOOKED UP TO IT TO SEE WHAT CYLINDERS ARE MISFIRING, 2 3 5 AND 8. I TOOK THE COIL PACK FROM ANOTHER CADILLAC TO SEE IF THAT WAS THE PROBLEM, BUT NO STILL IT MISFIRES. HELP!!!!
Submitted: 6 years ago.
Category: Cadillac
Expert:  Dave Nova replied 6 years ago.
Are the misfires constant, or intermittent? Do they occur more when the engine is cold, or hot? Do they occur more when the engine is under load, such as when accelerating?
Customer: replied 6 years ago.
it does it at idle and under load. . .more under load tho cylinders 5 and 8 at idle and clyinders 2 3 5 and 8 under load,
Customer: replied 6 years ago.
its a 2003 deville, like i said i replaced the plugs and wires, still misfired . . . .swaped coils with another cadillac here and still misfired, it does it under load more than idle. . .at idle clyinders 5 and 8 misfire, under load 2 3 5 and 8 misfire.
Expert:  Dave Nova replied 6 years ago.
What are your fuel pressure readings?
Customer: replied 6 years ago.
fuel pressure is fine, that was the first thing i checked. i am just confused right now. . .and im tired of tinkering with this cadillac. do you think it could be a clogged cat?
Expert:  Dave Nova replied 6 years ago.
It could be a clogged cat. Try dropping the exhaust pipe at the manifold and running the engine to see if the misfires go away.

Related Cadillac Questions