Can a vacuum leak cause multiple cylinder misfires and a lean code?
A vacuum leak lets unmetered air into the engine, causing a lean running condition like code P0171 and multiple cylinder misfires. This often happens alongside exhaust sputtering, and replacing basic ignition components like spark plugs and wires alone will not resolve the underlying air or fuel delivery issue.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
Found another way around this?
Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.
- 1changing plugs and wiresDid this help you?
- 2cleaning the MAF sensorDid this help you?
- 3cleaning plug threads and blocks with brake cleanerDid this help you?
- 4cleaning soot off spark plugsDid this help you?
- 5diagnosing under the hood instead of at the tail pipeDid this help you?
- 6looking for a shake that is out of time with everything elseDid this help you?
- 7Disconnecting individual ignition coils to test rev dropsDid this help you?
- 8Checking coil resistance with a multimeterDid this help you?
- 9Inspecting for oil leaks around the top end and sensorsDid this help you?
- 10Swapping coil packs between cylinders to see if the code followsDid this help you?
- 11Swapping spark plugs between cylindersDid this help you?
- 12Cleaning a dirty spark plugDid this help you?
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“hello, I have a Kia Ceed 2 2014 and I’ve just noticed a bit of a sputter at the exhaust does this sound like the start of a misfire?”source ↗
“Does the sound of what’s going on with this car being consistent with the misfire on cylinder three or does it sound completely unrelated or something else?”source ↗
“So to fix the misfire issue, i changed the plugs and wires and now i have a misfire in cylinders 2,5, and 6, and still the P0171.”source ↗
“Would a vacuum leak cause 3 cylinders to misfire and the truck to run lean?”source ↗
“While driving once it hits hirer revs the dashboard light begins to flash. Feels like the car has was less power / acceleration (2/3 thousand revs). I believe this is because it's misfiring.”source ↗
“Before bringing back to mechanic any ideas what I could try to further diagnose? Maybe spark plug gaps? Keep in mind I've no OBD code tester”source ↗
Where this came up
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