Intermittent misfires are one of the trickiest vehicle problems to track down. You have to get the car to do it while you’re working on it. SureTrack community member cbrodskysr had an Audi A4 in their shop that had a misfire under load, they did some work to it that seemed to clear up the issue but it came back in a few weeks with the same problem. They posed the question to the community, and with the help of fellow community member Ericsautomotive and others, they were able to resolve the issue quickly.
The following Community Fix summarizes the interaction between members of the community that led to the solution.
Vehicle
2015 Audi A4 Quattro 2.0L
Title
Misfire while accelerating/under load, replaced valve spring.
Complaint
Customer complains that engine runs rough at time, check engine light on.
Diagnostic Steps Performed/Parts Replaced
Vehicle came in a few weeks ago for an intermittent misfire concern. Vehicle short test showed random/multiple cylinder misfire and cylinder 4 misfire. At that time, I replaced spark plugs and performed a carbon cleaning. Road tested the vehicle and no faults returned. Vehicle came back in today with same faults. Removed and inspected ignition coils and plugs. Found no damage/defects. Performed compression test and leak down test. All readings were good. Swapped plugs on cylinders 1 and 4 and coils on cylinders 3 and 4. Cleared faults and performed road test. While accelerating, misfire was noticeable and MIL came back. Per secondary short test, faults recorded are P0300-00: Random/Multiple Cylinder Misfire, P0304-00: Cylinder 4 Misfire, and P130A-00: Hide Cylinder.
Removed and replaced all injectors. While intake was off, went ahead and did a secondary cleaning on the intake valves for carbon. Reassembled and road tested. Under “normal” driving conditions, car runs fine. As soon as vehicle accelerates, to pass another vehicle for example, misfire on cylinder 4 is present and very noticeable. At this point, based on what information I have available, I am at a loss. Tearing it back down to reinstall the original injectors since they didn’t fix the concern and there’s no reason for owner to pay for parts that aren’t needed.
Best Answer from Community Member Ericsautomotive
Valve train issue would be the only other thing I can think of.
Cause
Started the deep dive for valve issues. Found valve spring broken and causing all the issues.
Correction
Repaired valbe spring, road tested vehicle and all concerns are gone.
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