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Misfire cylinder 5, about to pull open engine as last resort!
03-10-2017, 07:36 AM, (This post was last modified: 03-10-2017, 07:37 AM by willisodhiambo.)
Post: #1
Misfire cylinder 5, about to pull open engine as last resort!
So a friends car F10 528i started with consistent cylinder 5 misfire occurring only under WOT. Car would shudder but get back to normal with normal driving. Over time it began to go into limp mode and would return to normal on restart. The misfire is worse as in it is now consistent and easy to trigger with spirited driving.

Coils swapped, no change, plugs swapped, no change, injector no 5 replaced with another from similar engine, no change. Compression tests OK, cylinder head cover changed. Inspected the intake thinking it could be the infamous coking of turbo engines. This one is sqeaky clean (528 being NA)! We are at our wits end. What comes to mind now are,

1. Faulty DME
3. Faulty harness
2. Worn or faulty compression ring

Anything else one can look for before the painful decision to dismantle the engine or replace a working DME? I just cant see what is special with cylinder 5 other than mechanical fault.
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03-10-2017, 07:51 AM,
Post: #2
RE: Misfire cylinder 5, about to pull open engine as last resort!
I had this annoying thing on my E60 530i and turned out to be a mibehaving lambda oxygen sensor on bank 1, precat. No lights on the dashboard, nothing. Just some misfire codes and that was it.

What engine do you have it's l6 N52/N53 or turbo N20 ?
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03-10-2017, 07:56 AM,
Post: #3
RE: Misfire cylinder 5, about to pull open engine as last resort!
Had this once with an E65, misfires on cylinder 7.
Checked everything and turned out to be the mass air flow sensor.
Cleaned it and problem solved.
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03-10-2017, 09:08 AM, (This post was last modified: 03-10-2017, 09:09 AM by willisodhiambo.)
Post: #4
RE: Misfire cylinder 5, about to pull open engine as last resort!
(03-10-2017, 07:51 AM)raduandrei82 Wrote:  I had this annoying thing on my E60 530i and turned out to be a mibehaving lambda oxygen sensor on bank 1, precat. No lights on the dashboard, nothing. Just some misfire codes and that was it.

What engine do you have it's l6 N52/N53 or turbo N20 ?

I6 N52. Was yours (misfire) also on one cylinder? Something I noticed and found strange. In ECU test I tried triggering the injectors. Well you know what? It fails to trigger and flags something about an environmental alarm or something like that. No error codes anywhere. Got me suspicious of oxygen sensor but why on earth is only cylinder 5 affected almost all the time? Are there two sensors pre and post cat?

(03-10-2017, 07:56 AM)beemered Wrote:  Had this once with an E65, misfires on cylinder 7.
Checked everything and turned out to be the mass air flow sensor.
Cleaned it and problem solved.

Mmmh! One more thing to try!
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03-10-2017, 10:02 AM, (This post was last modified: 03-10-2017, 10:05 AM by raduandrei82.)
Post: #5
RE: Misfire cylinder 5, about to pull open engine as last resort!
For me it was random, but in the same bank where the oxygen sensor was playing around. Only on last 3 cylinders (bank 2). Mainly on cylinder 4, then i had on 5, then on all 3, and then the code with "misfire on multiple cylinders".

One important note: the misfire for me happened only when i floored the gas, when driving normally, the car wouldn't have any symptom.

On N52's , the oxygen sensors have 4 pins, which means they also run when they are cold, unlike other engines that use preheat for oxygen sensors and they are reporting values only when hot.

N52 has 4 oxygen sensor, 2 for each bank, 1 precat and 1 aftercat.

Try to clean the MAF as it has been said, but i doubt a dirty MAF will cause this behavior. Next, try to disconnect the PRECAT oxygen sensor which corresponds to cylinder 5 (bank 2, it's on the second exhaust manifold towards the back of the car as you look from the right fender side to the engine), so ECU will use the default map when sensor is disconnected, see how the car drives.

Also note that PRECAT sensors are doing the job, the AFTERCAT sensors are just for monitoring.


(03-10-2017, 09:08 AM)willisodhiambo Wrote:  
(03-10-2017, 07:51 AM)raduandrei82 Wrote:  I had this annoying thing on my E60 530i and turned out to be a mibehaving lambda oxygen sensor on bank 1, precat. No lights on the dashboard, nothing. Just some misfire codes and that was it.

What engine do you have it's l6 N52/N53 or turbo N20 ?

I6 N52. Was yours (misfire) also on one cylinder? Something I noticed and found strange. In ECU test I tried triggering the injectors. Well you know what? It fails to trigger and flags something about an environmental alarm or something like that. No error codes anywhere. Got me suspicious of oxygen sensor but why on earth is only cylinder 5 affected almost all the time? Are there two sensors pre and post cat?

(03-10-2017, 07:56 AM)beemered Wrote:  Had this once with an E65, misfires on cylinder 7.
Checked everything and turned out to be the mass air flow sensor.
Cleaned it and problem solved.

Mmmh! One more thing to try!
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[+] 2 users say Thank You to raduandrei82 for this post
03-10-2017, 11:42 AM,
Post: #6
RE: Misfire cylinder 5, about to pull open engine as last resort!
Well noted. Ill test and report back.
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04-10-2017, 04:39 AM,
Post: #7
RE: Misfire cylinder 5, about to pull open engine as last resort!
1. Faulty DME => u should reflash it again first
3. Faulty harness => it should set fault code of miss communication
2. Worn or faulty compression ring => do a compression test or cylinder leakage test..that is the best method before take it a part

Please hit Reputation button if u think my info is helpful.
Regards
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04-10-2017, 08:46 AM,
Post: #8
RE: Misfire cylinder 5, about to pull open engine as last resort!
(04-10-2017, 04:39 AM)nguyennhatquang Wrote:  1. Faulty DME => u should reflash it again first
3. Faulty harness => it should set fault code of miss communication
2. Worn or faulty compression ring => do a compression test or cylinder leakage test..that is the best method before take it a part

Compression test has shown all OK, DME flash will be included. Someone also suggested faulty head gasket but I would expect that to show up in compression test or coolant consumption.
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04-10-2017, 09:43 AM, (This post was last modified: 04-10-2017, 09:48 AM by JarsaR.)
Post: #9
RE: Misfire cylinder 5, about to pull open engine as last resort!
Hey,

I see you have tried with second hand injector,
but what if you change this cylinder 5 injector to other cylinder? thinking
Injector is quite a common problem on this N53.
Is the chain timing OK?
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04-10-2017, 12:14 PM,
Post: #10
RE: Misfire cylinder 5, about to pull open engine as last resort!
(04-10-2017, 09:43 AM)JarsaR Wrote:  Hey,

I see you have tried with second hand injector,
but what if you change this cylinder 5 injector to other cylinder? thinking
Injector is quite a common problem on this N53.
Is the chain timing OK?

Not bothered with that yet. We have been reasoning that timing would affect all cylinders, not just one. Will swap injectors all over and retest.

By the way, timing is via gears and chain. How exactly can it slip? I have never understood how such a thing can happen at all on a car with steel chain
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