Code P0300 and acceleration low

DYLAN KING

MEMBER
2007 CHEVROLET SUBURBAN
5.3L
V8
2WD
AUTOMATIC
250,000 MILES

Engine has 140,000 miles after piston rings replaced and both heads done. Spark plugs and wires changed with new GM brand 6,000 miles ago. Now check engine blinks and traction control message pop up. The code P0300 showed up and acceleration is low to none at some point. Timing is getting lower from 15 to 16 degrees to 10 or 9 degrees when try to accelerate fast and cylinders five and seven show the most misfiring. When engine running at park position looks normal and does not show misfiring.
Any advise please?

3 Replies

ASEMASTER6371

MECHANIC
52,797 POSTS

Good morning.

The first thing I would do is to check the fuel pressure. The 300 code is common for low fuel pressure causing engine multiple misfires. There is a access port on the fuel rail to check the pressure.

Roy

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Monday, January 29th, 2018 AT 5:42 AM

DYLAN KING

MEMBER
2 POSTS

Hi,
thanks for your answer. I did measure and its stay steady with no drops when accelerate rpm and am running on very reach mixture. Checked the manifold and no hesitation on the gauge. I did change the crankshaft sensor, but did not change anything. I ordered a new camshaft sensor to see if will fix it.
Any other suggestions please?

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Wednesday, January 31st, 2018 AT 9:55 AM

ASEMASTER6371