2003 Chevrolet Suburban 5.3 Automotive Misfire

Another 2011 update class completed, for every one who attended, thank you so much for coming back.

Now let’s talk about our nightmare we had this week.

2003 Chevrolet Suburban 5.3 Misfire

2003 CHEVROLET Diagnoses Codes for O2 sensor and misfire

This vehicle came in to the school with a misfire that failed smog check, so we went through are regular routine sequence, the Chevrolet Suburban also has a service engine soon light on for PO300 random misfire, P1153 – P1154 O2 sensor circuit.

Here is what we found in our diagnoses:
Replace Fouled Plugs and Spark Plug Wires
Clean Injectors “no charge”
One of the O2 sensors had open heater circuit internally replace both Pre O2 sensors; the other one due to mileage, the vehicle has 175,000 miles on it.
Repaired one sensor threads worn out due to age
Check compression – good – 150 psi
Check running compression – good – 60-65 psi
Check Vacuum – good – 17 – 18” of vacuum.
Check fuel pressure and regulator – good – 60 psi

Check fuel pressure regulator for fuel leaks, which is very common, there were known
Check and repaired vacuum leaks
Check coil output with spark test “ST-125” – all coils check out good
We Check coils – good – by switching them with known good one from another cylinder to be sure. As a side note if a coil can ignite a spark tester, “st125” set at 30kv it I probably good.
We also check primary amperage on the coils, which also looks good.

Perform fuel volume test on Injectors they also pass.
Clean Injectors at No charge hoping the spray pattern is causing the misfire, it wasn’t.
We also check injectors by switching them with known good one from another cylinder, out of desperation, again this didn’t take care of the problem.

Check charging system – good – no leaking AC Voltage and it’s charging over 13.5 volts which is good.

The process continues tomorrow with the Chevrolet Suburban from hell.

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