E46 328i misfires on cylinders 1-3

[phelix]

I'm getting misfires on cylinders 1-3 with no apparent pattern. They're sometimes also accompanied by an o2 sensor out of range on bank 1. I can clear the codes and they reappear with different cylinders but always in Bank 1. Here's what I've done to diagnose so far:

replaced the plugs (no change)
swapped coils 1-3 with 4-6 (no change)
tested the continuity of the ignition wiring harness (all wires tested OK)
inspected the coils (all look OK - original Bosch parts)
checked the resistance of the coils (all about 0.6 ohms)
checked the resistance of the plug connectors (all about 2000 ohms - about double what they should be for Bosch parts according to the Bentley manual)
checked the fuel pressure (3.7 bar at idle - spec is 3.5 bar +/- 0.2 bar)
checked the 2 intake boots (original and in remarkably good condition)
cleaned the MAF (no change)
ran with the MAF disconnected (perhaps ran slightly better but hard to be sure)

Still to do:

replace the fuel filter (due to be done soon anyway)
check the fuel delivery rate

The car is a 99 E46 328i with 130K miles. The misfire occurs from a cold start. The breather valve and related hoses were repalced about 6 months ago.

I'm a little nervous that it's only cylinders 1-3 having problems. I suppose I can check and/or swap the injectors but that the fault is staying with cylinders 1-3 makes me wonder if the ECU is having a problem firing those coils?
Any thoughts/ideas appreciated.

[Neomagic]

Odd one that indeed, I'm surprised you haven't cured it already with the steps you have already taken.

Get it down to a friendly garage and plug it in I say.

[phelix]

When you say plug it in what are you thinking of? I have read and reset the codes via Carsoft.

[Vixpy1]

Change the Lambda sensor?

[phelix]

Not sure the lambda sensor matters as the problem occurs even from a stone cold start when the car's running open loop.

[Vixpy1]

In which case i would change the MAF, cleaning them is usually a non starter in my experience

[Shropshiremike]

phelix said:

Not sure the lambda sensor matters as the problem occurs even from a stone cold start when the car's running open loop.

Could you try swapping the lambda sensors over ( I presume the E46 is on twin sensors like the E36 )- especailly as it is reporting a sensor out of range as you say. If it still does it on those same 3 it might be a wiring fault. If it affects 4-6 and 1-3 are better it might be the sensor you just swapped......

Either way, a cheap trial....

Edited by Shropshiremike on Wednesday 21st January 19:58

[< FORZA WEST]

The O2 sensor out of range....does it say its too lean or rich end stop?

The clue will be in what it says there...

[phelix]

The laptop crashed and I didn't write the O2 sensor code down so I need to wait for it to reappear.

I noticed that at idle there's no vacuum at the hose going to the fuel pressure regulator at the end of the fuel rail - that seems odd.

[phelix]

Eventually the fault settled down to only a misfire on cylinder 2 with no other codes. Swapped injectors 1 and 2 with no change. It turned out to be nothing more than a bad coil. I did a compression test (all 195 psi +/- 5 psi) and moved the coils around again and this time the error code moved with the coil. Not sure why the initial error codes were as "scattered" as they were?

Edited by phelix on Monday 9th February 06:16