No acceleration Read codes, PO300, PO303?

2011 CHEVROLET EQUINOX

195,000 MILES • 2.4L • AUTOMATIC

FREERIDER78

MEMBER
23 POSTS

Read codes, PO300, PO303, coil swap with 2, found oil in plug wells and carboned up plugs. Replaced valve cover gasket and well seals and plugs. Gapped. 035 iridium. No CEL flashing or codes but permanent PO300. When driving no acceleration. After repair initially seemed OK. Then checking deeper for codes PO302. Swap with 1. When pressing gas pedal several times while parked and idling a large cloud of smoke, oil, emitted and then dissipated. Acting like a plugged cat which was replaced with aftermarket unit. Exhaust smells like sulfur. Oil doesn't smell like gas. Suspecting plugged cat. Don't think it's HPFP, no code and no injector code. Lastly there seems to be both vacuum and pressure at the oil cap. Is that normal? Haven't run compression test or fuel pressure test but there's definitely pressure at the rail when I depressed the Schrader valve. Stumped.

Jul 27, 2026 at 4:27 AM

STRAILER

✓ASE Certified Mechanic
54,832 POSTS

It would help if you can upload a video of the engine running so I can see it. The oil can be when you changed the spark plugs and valve cover gasket and should burn off. The spark plug being black can indicate the cat is plugged and lowering engine vacuum when will richen the mixture making the problem worse. Here is a video to help you check the catalytic converter.

https://www.youtube.com/watch?v=kNXh1Lphzr4

Also, if the misfire follows the bad ignition coil change it out with a new one. If the engine makes a tapping noise at idle the HPFP could be going out or the camshaft lobe that drives the pump might be worn as well. If there is a noise, (this is why I want the video) I would remove the HPFP and inspect the camshaft lobe. Please let me know what happens.

Jul 27, 2026 at 6:00 PM

FREERIDER78

MEMBER
23 POSTS

Ok next time I'm there I will get a video. There is definitely a noise but doesn't sound like chain rattle. More like lifter or such. Passenger side of engine on top. I didn't listen directly on the HPFP. I'm also not positive if it followed the coil or not. I'll be back there in a few days and will update you. They're supposed to be talking to the shop that did the cat and having it checked.

Jul 27, 2026 at 7:13 PM

STRAILER

✓ASE Certified Mechanic
54,832 POSTS

Sounds good but yes the engine noise can be the high pressure fuel pump or the camshaft lobe is worn down. Let me know.

Jul 28, 2026 at 12:32 AM

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