Random misfire code P0300
Thread Starter
Intermediate
Joined: Jun 2018
Posts: 34
Likes: 3
Random misfire code P0300
i bought a 2008 auto C6 with 140,000
the car is in great shape and the motor is very strong.
It has a randomn misfire while idle and it clears up under load
so far I have
replaced
all 8 fuel injectors ( AC Delco )
new plugs and wires ( AC Delco )
all 4 new O2 sensors ( AC Delco )
had valve cleaning done
new battery
so had fuel pressure test and it came back at 61 lbs which by the book was great
what else could it be. Please help
dealer has the car and 1 dealer done turned me away saying they couldn’t find the fix. This dealer is trying they are now leaning to it needs a valve job.
The motor doesn’t smoke or knock at all.
the car is in great shape and the motor is very strong.
It has a randomn misfire while idle and it clears up under load
so far I have
replaced
all 8 fuel injectors ( AC Delco )
new plugs and wires ( AC Delco )
all 4 new O2 sensors ( AC Delco )
had valve cleaning done
new battery
so had fuel pressure test and it came back at 61 lbs which by the book was great
what else could it be. Please help
dealer has the car and 1 dealer done turned me away saying they couldn’t find the fix. This dealer is trying they are now leaning to it needs a valve job.
The motor doesn’t smoke or knock at all.
Safety Car
Joined: Dec 2006
Posts: 4,587
Likes: 1,667
From: Pearland / Houston Tx
From the shop manual:
• A misfire may only occur when the engine is operating under a load or when the engine is cold.
• A high resistance condition on any ignition control (IC) circuit can cause an engine misfire P0300-P0308 DTC to set, without setting an IC circuit P0351-P0358 DTC.
• This test procedure requires that the vehicle battery has passed a load test and is completely charged. Refer to Battery Inspection/Test .
• A misfire DTC could be caused by an excessive vibration from sources other than the engine. Inspect the following for possible sources of vibration:
- A tire or wheel that is out of round or balance
- Variable thickness brake rotors
- An unbalanced drive shaft
- Certain rough road conditions
- A damaged accessory drive component or belt
- A damaged reluctor wheel
- The Crankshaft Position System Variation Learn procedure may need to be performed.
• A misfire may only occur when the engine is operating under a load or when the engine is cold.
• A high resistance condition on any ignition control (IC) circuit can cause an engine misfire P0300-P0308 DTC to set, without setting an IC circuit P0351-P0358 DTC.
• This test procedure requires that the vehicle battery has passed a load test and is completely charged. Refer to Battery Inspection/Test .
• A misfire DTC could be caused by an excessive vibration from sources other than the engine. Inspect the following for possible sources of vibration:
- A tire or wheel that is out of round or balance
- Variable thickness brake rotors
- An unbalanced drive shaft
- Certain rough road conditions
- A damaged accessory drive component or belt
- A damaged reluctor wheel
- The Crankshaft Position System Variation Learn procedure may need to be performed.
Thread Starter
Intermediate
Joined: Jun 2018
Posts: 34
Likes: 3
The first dealer did. But they too was the one that told me to come get it they couldn’t figure it out.
The new dealer is very slow and doesn’t communicate very well. I. My area it is hard to get people who knows what they are doing and will do it
The new dealer is very slow and doesn’t communicate very well. I. My area it is hard to get people who knows what they are doing and will do it
