Evap issue (small leak)
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Joined: Jan 2020
Posts: 6
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2014 C250
Evap issue (small leak)
Hey all,
I have a 2018 C63amg (base, not S)
few weeks back I had a gas cap loose notification.
Obviously tightened it, but it wasn’t loose to begin with.
about a week later I went to get gas (shell) and filled up the car like normal.
i turned on the car and it idled rough enough to where my wife and I looked at each other like what’s going on.
then the check engine came on flashing.
i turned off the car, and then waited a few minutes and turned it back on.
there was no check engine light or anything.
things were fine for a few weeks when the check engine light came on again.
checked it with my obd reader and it said I had an Evap error (small leak)
I changed the gas cap yesterday and reset the light. It came back on again today.
its not had any issues of rough idling since that first time, but am a bit concerned here about.
any thoughts guys?
thank you!
I have a 2018 C63amg (base, not S)
few weeks back I had a gas cap loose notification.
Obviously tightened it, but it wasn’t loose to begin with.
about a week later I went to get gas (shell) and filled up the car like normal.
i turned on the car and it idled rough enough to where my wife and I looked at each other like what’s going on.
then the check engine came on flashing.
i turned off the car, and then waited a few minutes and turned it back on.
there was no check engine light or anything.
things were fine for a few weeks when the check engine light came on again.
checked it with my obd reader and it said I had an Evap error (small leak)
I changed the gas cap yesterday and reset the light. It came back on again today.
its not had any issues of rough idling since that first time, but am a bit concerned here about.
any thoughts guys?
thank you!
Last edited by Josh Herman; Dec 19, 2025 at 05:18 PM.
Member
Joined: Jan 2024
Posts: 201
Likes: 60
From: Colorado
2018 C63S AMG Coupe, 2019 Jaguar F-Pace SVR
Post the code from the OBD reader, and that might help us diagnose. Unfortunately these cars are very complex with regard to all the modules and electronics, and the code could give everyone a jumping off point.
In the meantime, you might also check your oil fill cap and that your oil dipstick is pushed in all the way. Either of those things can cause a vacuum leak too. There's also the pesky evap solenoids ("Purge Control Valve") at the front of the vehicle. There are a ton of threads about those. Most people just don't like the ticking noise they make, but they can also fail, causing rough idle, hard starts, poor MPG, and a Check Engine Light (CEL) with codes like P0441, P0443, P0455.
Here's a video on the purge valves (just the first 1:30 or so.. the last part of the video is just the guy walking around the shop).
In the meantime, you might also check your oil fill cap and that your oil dipstick is pushed in all the way. Either of those things can cause a vacuum leak too. There's also the pesky evap solenoids ("Purge Control Valve") at the front of the vehicle. There are a ton of threads about those. Most people just don't like the ticking noise they make, but they can also fail, causing rough idle, hard starts, poor MPG, and a Check Engine Light (CEL) with codes like P0441, P0443, P0455.
Here's a video on the purge valves (just the first 1:30 or so.. the last part of the video is just the guy walking around the shop).
