2004 Chevy Silverado Missfires on left bank

Tiny
TXFIREFIGHTER
  • MEMBER
  • 2004 CHEVROLET SILVERADO
  • V8
  • 2WD
  • AUTOMATIC
  • 34,000 MILES
I have a 2004 silverado 1500 5.3L that I took to the dealership I purchased it at to have it checked. It was ideling very rough. When they ran diagnostics on it, it came back with P0300 code and missfire counts on cylinders 1, 3, 5, 7. (The entire left bank) Cylinder 1 had 40,000 missfires and they intermittenly decreased to 16,000 on cylinder 7.

This thing idles rough, at road speeds it's fine.
I took the throttle body off and cleaned it really well, checked for vaccum leaks on the intake manifold. No problems I could find there. Spark pllugs are all good.

The service techincian had no clue what to do with it.
I searched on the net and found that this is becoming a problem with this motor, but no one seems to be able to figure out how to fix it.

You guys have any clues?
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Saturday, March 7th, 2009 AT 3:34 PM

2 Replies

Tiny
BRIAN 1
  • MEMBER
I've had this problem before, try this info: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 from SI.
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. Also perform an exhaust back pressure test on that bank, a plugged cat converter can cause this also. Post back with what you find.
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Saturday, March 7th, 2009 AT 7:54 PM
Tiny
TXFIREFIGHTER
  • MEMBER
Ok, Did like you said, started by flipping the o2 sensors. Bingo! New O2 sensor and bam. Problem fixed! Thanks!
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Thursday, March 12th, 2009 AT 9:36 PM

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