Hi all!
Recently I've started to experience a really rough idle when cold on my 2018 Leon Cupra (EA888 engine, CJXC), so I'm sharing a fix with some data:
There are many reasons for a rough idle, from a dirty intake manifold, defective throttle body, injectors, spark plugs, you name it.
In my case, the problem went away when the engine warmed up, and I had zero error codes! The cause of the issue was the cam adjustment magnet on the intake side, the little pin that actuates the valve was kinda stuck and wasn't moving freely when I removed the adjustment magnet and tipped it up and down. I'm guessing when the engine warmed up, it warmed up the magnet too and it was easier to move, so the problem went away one the car got up to temp.
I logged the data using OBDeleven before and after changing the magnet.
The data points are:
- Specified Cam adjustment on the intake side (camshaft degrees requested by the ECU) BLUE on my charts
- Actual Cam adjustment on the intake side (actual position as read by the position sensor) RED on my charts
these two should be roughly the same, with only minor variations.
Here's a chart before changing the magnet:
and after:
as you can see before changing the magnet the actual degrees were WAY off, especially at the 15° mark, when the car is idling.
If you're experiencing something similar, test for yourself if you can, the fix is super simple and cheap, the new magnet I used is a FEBI BILSTEIN 40198 and it only cost 25€. Many other manufacturers available for this part if you so choose. The only thing you need to change it is to unplug it, and unscrew the three torx screws holding it in place. You can even test the old one, if you hold it upside down, the central pin should move freely up and down. When Inserting the new one, just watch out that the two o-rings are in place on the belt cover!
Now this isn't the only possible issue when having a rough idle with this kind of data, it's also possible the valve that this magnet actuates is stuck or broken. The valve is right behind the magnet on the engine, so if you remove the magnet actuator you can see it:
the circular pad in the middle is what the pin on the magnet moves! It should be flush wit the the surrounding housing and you can easily press it in with your finger, and it should spring back out to this position easily! If not consider changing this part too, but you need a special tool for this. The valve uses engine oil to operate, so it's sensitive to dirty oil, or oil with thicker viscosity.
Hope this helps someone, since I couldn't find data like this online!
full data in this excel file: https://docs.google.com/spreadsheet...ouid=108891579655749839371&rtpof=true&sd=true
Recently I've started to experience a really rough idle when cold on my 2018 Leon Cupra (EA888 engine, CJXC), so I'm sharing a fix with some data:
There are many reasons for a rough idle, from a dirty intake manifold, defective throttle body, injectors, spark plugs, you name it.
In my case, the problem went away when the engine warmed up, and I had zero error codes! The cause of the issue was the cam adjustment magnet on the intake side, the little pin that actuates the valve was kinda stuck and wasn't moving freely when I removed the adjustment magnet and tipped it up and down. I'm guessing when the engine warmed up, it warmed up the magnet too and it was easier to move, so the problem went away one the car got up to temp.
I logged the data using OBDeleven before and after changing the magnet.
The data points are:
- Specified Cam adjustment on the intake side (camshaft degrees requested by the ECU) BLUE on my charts
- Actual Cam adjustment on the intake side (actual position as read by the position sensor) RED on my charts
these two should be roughly the same, with only minor variations.
Here's a chart before changing the magnet:
and after:
as you can see before changing the magnet the actual degrees were WAY off, especially at the 15° mark, when the car is idling.
If you're experiencing something similar, test for yourself if you can, the fix is super simple and cheap, the new magnet I used is a FEBI BILSTEIN 40198 and it only cost 25€. Many other manufacturers available for this part if you so choose. The only thing you need to change it is to unplug it, and unscrew the three torx screws holding it in place. You can even test the old one, if you hold it upside down, the central pin should move freely up and down. When Inserting the new one, just watch out that the two o-rings are in place on the belt cover!
Now this isn't the only possible issue when having a rough idle with this kind of data, it's also possible the valve that this magnet actuates is stuck or broken. The valve is right behind the magnet on the engine, so if you remove the magnet actuator you can see it:
the circular pad in the middle is what the pin on the magnet moves! It should be flush wit the the surrounding housing and you can easily press it in with your finger, and it should spring back out to this position easily! If not consider changing this part too, but you need a special tool for this. The valve uses engine oil to operate, so it's sensitive to dirty oil, or oil with thicker viscosity.
Hope this helps someone, since I couldn't find data like this online!
full data in this excel file: https://docs.google.com/spreadsheet...ouid=108891579655749839371&rtpof=true&sd=true
