240k miles, changed spark plugs about 50k miles ago. Upon startup (cold), rattle, shake engine noise. Codes: P0300, P0301 and P0302. Checked ignition coils with ohm meter, ea registered w/ btwn 12 and 20ohms. Thinking fuel injectors, but not sure.
Why do you think it's fuel injector related? Ohming out ignition coils isn't going to tell you anything - unless they are completely open or shorted. You'd have a definite misfire that you would've easily found. If you can smell gas while you were trying to start and run the car; that kind of rules out injector and fuel pump issues. Reverse the order of the coils to see if your problem moves - that should isolate a coil issue. Pull the plugs to see how each cylinder is burning, they should be uniform in color and consistency. If your using crappy Bosh plugs; go back to ND or NGK. My ignition coils began failing on my GMC, one at a time around that mileage. I had to wait 18 months, for the coil to completely fail, to find it. Every-time it misfired, I'd pull over to try to find it and it would go away. No CEL, but a definite loss of power and I can feel the misfire. When I started getting another intermittent misfire after changing the first dead one; I replaced all of them - no more issues. Check your engine compartment for a nest and chewed wiring harness Hope this helps...
Thank you, I appreciate it. I'll try reversing the ignition coils as you suggested. Then I'll look at the plugs.
My coolant level is good. I first suspected a head gasket issue. Coolant level is fine and oil is normal color and thickness. Just had oil changed about 1k miles ago. Never touched the egr circuit. That might come after the ignition coils.
50k miles....just about the perfect distance for chinese counterfeit spark plugs tips to be disintegrated... it would be worth checking them a good iridium plug should still look practically new unfortunately, this: startup (cold), rattle, shake engine noise. Codes: P0300, P0301 and P0302. in a Gen 3 seems to commonly be due head gasket problems. hopefully not for you.
Bisco these cars rarely if ever leak coolant into the oil. They leak into the cylinder when cold causing the plugs to foul and misfire. If it clears and runs fine in under a minute it has the dreaded gen3 hg cancer.
Mark coolant level with marker or tape. This is most likely the Dreaded Head Gasket. It's the perfect mileage for it. It's almost guaranteed to blow on your engine. Mine and many others have. Rattles then clears up is the head gasket.
