» » »

Chevrolet Q&A

Ask Your Question

1999 Chevrolet Tahoe Question: Has a stumble at idle and getting on the gas! codes po 300 & 307.

 

Question

mikeyb4, 5.7L V8, Menifee, CA, March 27, 2013, 17:46
Profile_thumbnail
 Rookie

Changed plugs cap & rotor.Number 7 plug all black and foil looking.Still has stumble and codes 300 & 307 came wright back. notice orange fire not blue or white. Changed coil.Same thing no change.The owner called a another shop.And he said intake pressure valve or burn't valve. Witch I was getting ready to do compression check.The new plug in number 7 was still white. And got 120 psi. All the rest of the plugs was showing signs of firing and 160 to 180 psi. I'm thinking burn't valve. Also smell gas while its running and lots of water out tail pipe and from muffler.Maybe cracked head or gasket

1 Answer
Flag This
  • Answer #1

    pushrod March 28, 2013, 05:45
    Profile_thumbnail
     Master

    120 psi should still fire that cylinder! Need to do an injector balance or a leakdown test. May be washed down with gas, smooth out at road speed? Number 7 plug wet when removed?

    Reply
    Flag This