Check engine light, horrible missing, P0300 code

JWIN9569

MEMBER
1995 GMC SIERRA
5.7L
V8
4WD
AUTOMATIC
196,500 MILES

I was leaving work just started hitting the incline going up the mountain an truck just began missing horribly shaking, bogs when giving it gas. Starts right away but misses while idling an even more severe when entering gears. The missing clears down hill until you begin attempting to accelerate resulting in bogging and shaking.

3 Replies

HMAC300

MECHANIC
48,601 POSTS

Scan for codes and check fuel pressure with a gauge auto parts rent it. Often times it is low fuel press that causes this as well as a vacuum leak so check for that as well. if it is tbi unit then it may be leaking vacuum at bottom of tbi front or rear. see link.
https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

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Tuesday, March 21st, 2017 AT 6:21 AM

JWIN9569

MEMBER
4 POSTS

Also 02 sensor code, fuel pressure is to spec. Still attempting to locate a vacuum leak any suggestions as to the most common fault areas. Also my mistake it is a 96'

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Tuesday, March 21st, 2017 AT 7:34 AM

HMAC300

MECHANIC
48,601 POSTS

If it is a 1996 fuel pressure must be 60-66 psi key on no lower otherwise it will cause a misfire. Check for spark at all cylinders and check around top sides of intake for leaks. Otherwise a mechanic will need to scan with his scanner to take readings of sensors as it could be that as well if not a low compression on one of the cylinders.

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Tuesday, March 21st, 2017 AT 8:28 AM