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2000 Yukon Denali: 5.7 vortec, I..check engine light..state inspection…

Customer Question
Help, I have a 2000...
Help, I have a 2000 Yukon Denali. 173000 miles. 5.7 vortec, I can not get the check engine light off for state inspection. Replaced fuel pump last fall, plugs wires cap and rotor in March. Has had a skip since. Shows obd II code 300.with #5 cylinder missing. replaced plenum and injector for #5 cylinder, still not better, if anything getting worse. compression on #5 is 120# XXXXX am at my witts end The only thing left to do is change injector assy. what do you suggest?
Submitted: 8 years ago.Category: Chevy
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Answered in 6 minutes by:
6/28/2010
Chevy Mechanic: Jettadan1, Chevy Technician replied 8 years ago
Jettadan1
Jettadan1, Chevy Technician
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Satisfied Customers: 5,064
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The following diagnosis might be helpful if the vehicle exhibits the symptom described in the PI.

Condition/Concern:

The vehicle may exhibit a SES Light due to a P0300 and misfire. If the misfire is related to the information below, it will typically happen while cruising uphill, pulling a trailer or on hard acceleration and then stop misfiring shortly after returning to an idle. Typically, cylinders 3, 4, 5 or 6 will be the ones to experience this.

Recommendation/Instructions:

If the P0300 SI diagnostics did not isolate a concern, the following may help:

Remove the valve cover, valve springs and valve seals on the effected cylinder or cylinders. A small wire tie or rubber bands can be placed in the valve stem keeper groove to prevent the valve from falling into the cylinder. Rotate the valve while moving it up and down in the guide to see if it binds. If a binding valve is found, remove both cylinder heads and use either of the following methods to increase the stem to guide clearance:

^Send the head out to a machine shop and advise them to increase the valve stem to guide clearance to 0.002 inch per guide.

 

^Hone the guide with a 9 mm hone, such as Snap On BCG249, until a clearance of 0.002 inch is obtained. This will usually take about 4 strokes of the hone.

 

Reassemble the cylinder heads using new valve seals.

Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance.

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Customer reply replied 8 years ago
actually the misfire is the worst at idle, although now it is a dead skip at cold start up and improves as the engine warms up. I also get a spark knock on long uphills and the condition seems to be worsening.
Chevy Mechanic: Jettadan1, Chevy Technician replied 8 years ago

Subject: 97-05 Vehicles with 4.8 5.3 5.7 and 6.0 Gen III V8 Engines and Misfires on One Bank - kw CEL diagnostics driveability DTC P0171 P0172 P0174 P0175 P0300 P0301 P0302 P0303 P0304 P0305 P0306 P0307 P0308 #PIP3056 - (07/12/2004)

Models: (00-05 Cadillac Escalade - C6 and K6) and (02-05 Chevrolet Avalanche - C1, C2 K1 and K2) and (99-05 Chevrolet Silverado - C1, C2 K1 and K2) and (00-05 Chevrolet Suburban - C1, C2, K1 and K2) and (00-05 Chevrolet Tahoe - C1 and K1) and (99-05 GMC Sierra C1, C2 K1 and K2) and (00-05 GMC Yukon - C1, C2, K1 and K2) and (03-05 Chevrolet Express G1, G2, G3, H1, H2 ) and (03-05 GMC Savana G1, G2, G3, H1, H2 ) and (04-05 Buick Rainier S1, T1 ) and (03-05 Chevrolet Trail Blazer EXT S1, T1 ) and (03-05 GMC Envoy XL XUV S1, T1 ) and (03-05 Hummer H2) and (04-05 Cadillac CTS-V DB) and (98-02 Chevrolet Camaro FB) and (97-04 Chevrolet Corvette YB) and (98-02 Pontiac Firebird FB) and (04-05 Pontiac GTO VB)

The following diagnosis might be helpful if the vehicle exhibits the described symptoms.

Condition/Concern:
Check Engine Light with a P0300 due to 2 - 4 cylinders misfiring on the same bank of the engine. DTCs P0171, P0172, P0174 or P0175 may also set for the misfiring bank.

Recommendation/Instructions:
If the published misfire diagnostic does not isolate the cause, perform the following suggestions as necessary:

  • Perform a fuel injector balance test for all 8 cylinders. If a fuel injector concern exists, it is possible to misfuel an entire bank of the engine, causing multiple cylinders on the same bank to misfire even though the root cause is a single fuel injector.
  • Inspect O2 sensor connections on the misfiring bank for corrosion or water intrusion. If water intrusion is found on the right bank, it may be due to the AC Evaporator Condensation dripping onto the O2 sensor harness. If this condition is found, reposition and shield the harness to prevent a repeat concern and repair the connections.
  • Check for excessive exhaust backpressure using the restricted exhaust diagnosis.
  • Swap the Position 1 O2 sensors side to side to see if the misfires move to the other bank of the engine. If so, replace the O2 sensor.

Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

NOTE: GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition.

here is a pdf on code 300 testing also.

 

 

http://www.mediafire.com/?gdz1gjjcdam

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