Rough idle

[Addy1183]

Ok I’m new here but not new to owning a tdi just new to the issues.
So a few weeks ago my car had an incident and started running extremely rough. And even had the rpms sky rocketing in certain gears. Fast forward we ran the codes and it said there were misfires or issues with the glow plugs in cylinders 3 & 4. So we changed those glow plugs actually found one that the tip was gone on. But since replacing them the rough idle has gotten a bit better but still is running tougher than normal.
Also runs rough at idle and up to 2200 rpms. Runs smoother at higher rpms.
So any help in figuring out this issue would be much appreciated.

 

[JohnTF]

Do a compression test - the parts of glow plug could have stuck / caught in valves ?
It's possible that the bits / pieces do not clear all at once , also the valve can bend , or get disturbed .
With the " idle has gotten a bit better " any damage may reseat , drive for a while , then do another compression test , if it does not continue to get better - it may have to come apart / head come off , maybe turbo , then you can see any damage etc.
Bits & pieces getting where they should not be and cause any number of issues .
If you can find a shop with a flex bore scope and see inside to look valves - almost impossible to see all the way around all the valves , but ???
Also look for scoring of the cylinders .
Good luck

 

[Addy1183]

Do a compression test - the parts of glow plug could have stuck / caught in valves ?
It's possible that the bits / pieces do not clear all at once , also the valve can bend , or get disturbed .
With the " idle has gotten a bit better " any damage may reseat , drive for a while , then do another compression test , if it does not continue to get better - it may have to come apart / head come off , maybe turbo , then you can see any damage etc.
Bits & pieces getting where they should not be and cause any number of issues .
If you can find a shop with a flex bore scope and see inside to look valves - almost impossible to see all the way around all the valves , but ???
Also look for scoring of the cylinders .
Good luck

How do you check the compression?

 

[JohnTF]

If you have to ask , take to a shop ;(

 

[JETaah]

Have the mechanic look at the camshafts to make sure that intake and exhaust are coordinated. A cylinder obstruction can cause them to lose their synchronicity. The gears on the opposite end of the pulley and lobes are shrink-fit to the shaft and can slip from position if a foreign object gets in between an open valve and the piston.