[shirkenikhil@gmail.com]

I've been encountering a concerning issue with my BMW 320D GT's engine performance. When I'm not accelerating, the engine rattles heavily, but at higher RPMs, it seems to run smoothly. Additionally, I've noticed lower mileage than usual.

Upon running diagnostics, I received the following error codes:

2A6D00 Permanent Smooth running Regulator Cylinder 4: Correction Quantity outside permitted Limit
2A6D00 Permanent Smooth running Regulator Cylinder 1: Correction Quantity outside permitted Limit
Here's what I've tried so far:

Replaced fuel injector No. 4 with a new one at Cylinder 4, but the error code persists.
Replaced injector 1 with a new one, yet the error code remains.
Cleaned the EGR system, but unfortunately, the error code persists.
Ensured there are no air leaks.
Even after resetting the diagnostics tools, the error codes persist, and the engine's performance suffers when not accelerating.

I'd greatly appreciate any insights or suggestions on what could be causing these issues and how to resolve them. Any pointer to a reputable mechanic in West London will help.


Thank you in advance for your help!

[TurboWeasel]

Assuming the new injectors were coded, it could be poor compression on 1 and 4 and the ECU is trying to compensate.

Boost tends to hide cylinder contribution issues.

[Eddamoo]

"the engine rattles heavily" - Does this mean like a knocking noise?

Ive seen a few threads where, unfortunately, crankshaft bearing failure has caused these 'smooth running' codes. If you're able, pull the oil/filter and inspect for bearing material.

[shirkenikhil@gmail.com]

not knocking noise but it shakes as if its not getting sufficient fuel.
When I put my foot on the accelerator pedal engine is fine.

[shirkenikhil@gmail.com]

Originally Posted by TurboWeasel

Assuming the new injectors were coded, it could be poor compression on 1 and 4 and the ECU is trying to compensate.

Boost tends to hide cylinder contribution issues.

Can you advise what can be done to fix the compression issue ?

[TurboWeasel]

I would take it in to expert for diagnosis before going down that road. If the rattling goes with revs, it might be slack chains.

[shirkenikhil@gmail.com]

I am told that the cylinder 4 could be damaged and cylinder 4 could be trying to compensate. To resolve this issue, the engine has to be dismounted and disassembled to check if valves or pistons are damaged. Either or both of them have to be replaced.

Can you please confirm if engine has to disassembled, do I take it to an authorised BMW garage and any indication on the costs to get this done through a BMW or an external reputed mechanic ?

And any recommendations on reputed mechanics doing this job ?

Thanks.

[Sasquartch]

Any decent specialist should be able to diagnose this properly

A compression test test would be a first step. If any anomalies are found then a borescope through the glow plug holes should be able to detect any serious engine damage.

As already stated check the oil filter for any metallic deposits.

Are the injectors OK ? Has a leak down test been done and all the pressures correct ?

Engine diagnosis over the internet is difficult (ie impossible to do accurately) - get it to a specialist and get some proper diagnosis carried out and go from there

[shirkenikhil@gmail.com]

Compression Test Results
Cylinder 1 - below 13 bar
Cylinder 4 - below 3 bar

Injectors are OK, Injector 4 is changed to new one.
I will ask them to check if the oil filter has any metallic deposits.

I doubt if they have check through a borescope, they are directly recommending to dismantle the engine to check further.

Is it better to take it to BMW or continue with this garage ?

Originally Posted by Sasquartch

Any decent specialist should be able to diagnose this properly

A compression test test would be a first step. If any anomalies are found then a borescope through the glow plug holes should be able to detect any serious engine damage.

As already stated check the oil filter for any metallic deposits.

Are the injectors OK ? Has a leak down test been done and all the pressures correct ?

Engine diagnosis over the internet is difficult (ie impossible to do accurately) - get it to a specialist and get some proper diagnosis carried out and go from there

[Sasquartch]

The fact that compression is not even across cylinders and low indicates a physical issue, eg piston/ring or valve or even head gasket. Although a stuck cam follower or whatever might cause the same issue
Yes it probably does need stripping down but a borescope would still be worth doing.