BMW E46 2006 318ci Misfire Problem

Jay P · March 16, 2020

Hi All, I need some urgent help as I am starting to lose hope!

Have an E46 2006 318ci coupe which has developed a misfire when under load at around 3-4k rpms where the engine light flashes for 10-15seconds and then disappears.

Car starts up perfectly everytime no shaking or juddering or cut off or stalling. Drives perfectly fine when below 3-4k rpms. Does feel a little sluggish however.

Diagnostics only list random misfires and misfires cyl 1 and cyl 4. No other codes showing up.

Changed all coils and all spark plugs. Moved them around into other cylinders to see if those cylinder issues also moved - no resolution

Had a fuel injector not working properly which was changed - no resolution

Two lambda sensors changed - no resolution

Smoke test - no issue with vacuum leaks

Compression test - no issues

Cat/pre car inspected - no issue with melting from hot fuel from misfiring

For background - I had the coolant expansion tank changed recently from which a few days later the misfiring started - any possible connection?

Have a minor oil leak - believe it's the sump or the vgc

No other issues mechanically.

Any advice or ideas Into what else I can check? I don't want to give up on the car but it's been out of action for nearly month now and my mechanic is struggling to find the problem.

Thanks for reading

Greydog · March 17, 2020

Morning Jay

I did read some time back about an issue like this that turned out to be a worn coil pack loom which was failing under load. Has your mechanic checked both the coil pack loom and injector looms ?

Good Luck

Dave

Jay P · March 17, 2020

14 hours ago, Greydog said:

Morning Jay

I did read some time back about an issue like this that turned out to be a worn coil pack loom which was failing under load. Has your mechanic checked both the coil pack loom and injector looms ?

Good Luck

Dave

Hi Dave,

Interesting suggestion, I will for sure pass that information on to him so he can check the wiring looms for both injectors and coil packs.

Is there individual ones for each coil and each injector? Or isit just one for all coils and one for all injectors? I havent looked into that much detail to know.

Thanks for the response

X5smw · March 18, 2020

I had an issue on an e36 with an m43 engine like this.
turns out it was the cam sensor (knock sensor) which is located on the drive belt pulley. Under load, the pulley it is on moved forward and. Stopped the sensor reading every couple of turns which caused a misfire. Try pulling and pushing all the pulleys on the belt at the front of the engine to make sure they are all right and not perished.

it was a right pain to diagnose

worth a go.

stu

Greydog · March 18, 2020

Check www.newtis.info for wiring diagrams which could give a clue

Jay P · March 18, 2020

Quick update the mechanic says his gut feeling is that it's a mechanical fault. He can't find any electrical faults and has checked wiring and the fact that it's driving sluggish even without the EML on/flashing when below 3-4rpms it would indicate a mechanical fault.

I guess my next question to you experts is, what are the possible mechanical faults that can cause sluggish power, and misfires with a flashing EML?

I will certainly mention the pulley which could be out of place as mentioned by X5smw.

Greydog · March 19, 2020

Depending on mileage the list is quite long, timing chain, injectors, fuel pump, fuel filter, failed or failing sensor, frayed loom to any of the sensors.

The car needs to have the fault codes read using a BMW specific scanner otherwise you are asking us to guess, the cost of changing parts will be crazy.

I would start with a code reading session

Dave

Jay P · March 19, 2020

Hi Dave,

The car has 80k miles on it.

The timing chain and guides were changed about a year and a half ago.

Also they changed one fuel injector which was failing the rest were fine.

The mechanic took the air system apart to see if there was any issues there and everything was fine.

He checked all the areas surrounding the coolant tank which I had changed to see if anything was out of place and all checked out fine.

Wouldn't sensor issues flag up sensor errors on diagnostics?

I don't have the ticking sound either to suggest sticking lifters.

He wants to take off the valve cover to investigate further but I have asked him not to as I don't want to spend any further money just on the investigation phase.

They used a reader which reads BMW codes and only the misfire codes show up. P0300 p0301 p0304 (random misfires, cyl 1, cyl 4)

😥

Greydog · March 19, 2020

Sorry Jay

But the fact that you have codes p0300 etc tells me it is a generic code reader not BMW specific those are general codes read from the DME

My reader (BMW 1.4.0) reads every module fitted to the car and gives a clear explanation of any faults in English as and example I currently have a fault with the rear parking sensors. The fault doesn't give a code it simply says "rear inner left sensor fault" in English there are 4 sensors 2 outer 2 inner so finding the offender is simple.

Get a BMW specialist to read the codes or ask if there is a member near you with a reader other wise you will just throw money at it.

Dave

Jay P · March 20, 2020

13 hours ago, Greydog said:

Sorry Jay

But the fact that you have codes p0300 etc tells me it is a generic code reader not BMW specific those are general codes read from the DME

My reader (BMW 1.4.0) reads every module fitted to the car and gives a clear explanation of any faults in English as and example I currently have a fault with the rear parking sensors. The fault doesn't give a code it simply says "rear inner left sensor fault" in English there are 4 sensors 2 outer 2 inner so finding the offender is simple.

Get a BMW specialist to read the codes or ask if there is a member near you with a reader other wise you will just throw money at it.

Dave

Hi Dave,

He told me has a reader capable of reading BMW specific codes 🤔 I will be questioning him on this if it isn't true! Thanks for the insight.

Greydog · March 20, 2020

Jay

Any OBD reader will read codes from the main modules and give a general code P0xxx, my X5 has 3 pages of readable modules and all modules have sub sections.

Google BMW 1.4.0 or BMW INPA or Carly for BMW there are many out there and look at some of the screen shots. The amount of information they give is vastly superior to general codes.

Jay P · March 31, 2020

Update:

So had another mechanic take a look who has a BMW tool and he read the hexadecimal codes (hexi? / Hexa?) And they are only showing multiple cylinder misfires. I didn't get a picture unfortunately.

He also updated the ECU software while he was at it.

He checked fuel pressure and flow which was fine @ 3.7bars

He checked the O2 sensors all reading fine and he did a back pressure test showing 20.30m/bars

He checked the entire air induction system which was all ok.

He checked vanos lines and swapped the control valves to see if any differences and all was ok.

He is the second mechanic to now say its not an electrical fault and if I want him to further test he will need to open up the engine which of course costs money.

On top of the diagnostics which have been done from previous mechanic which I listed above he has done additional tests.

I brought the car back and fired it up without any issues. Sounds fine. Runs fine. Fuel consumption is fine. No wierd noises. No stalling or engine juddering or fuel cut off. Can't hear any wierd noises from the engine bay and neither could the mechanic. Drives perfectly fine when driven at around 40-50mph. Slowly pressing the accelerator the car picks up speed but is missing the punchy feeling of immediate throttle response, it's more of a steady pick up in speed.

Go over 3500-4000rpms with foot down the car starts to hesitate and misfires and loses power. Engine light flashes then Dissapears after 15seconds approx.

Is there anything I can check myself without needing to open up the head? I'm no mechanic but I could possibly check some simple things as a starting point?

I have experienced a bad timing chain couple years back because of the metallic horrible sound from the engine and constant EML and limp mode. I do not have this currently.

Would a chain tensioner going bad throw up limp mode and a horrible sound? Or would it be more undetectable unless you removed the bolt to check?

Sorry for the long message. And thanks for any responses

Jay P · March 31, 2020

Also would it be worth checking the basics again? Like the coils and spark plugs in case they are faulty? They were all changed from the previous mechanic plus one fuel injector which was sticking the rest were fine so weren't changed.

Jay P · March 31, 2020

I have also read online in many forums that sometimes bad cam sensors or crank sensors can cause power loss and misfires and they also sometimes don't show up as fault codes. How can I check that these sensors are working?

Greydog · March 31, 2020

Hi Jay

Have a look at www.newtis.info you should find the test values and schedules for sensors there.I still think it is a failing loom insulation breaking down under load

Dave

X5smw · March 31, 2020

Cam sensors can be found on the pulleys. I had an issue with one.

the sensor is located on the large pulley at the base of the engine. The rubber anti vibration art had perished and I could pull the pulley forward and backward on its shaft.
try all the pulleys by hand. It will be obvious if one has failed.

As greydog says, check the earth mounting on the engine and the connectors on the loom.
This might seem innocuous but plays an important part.

Jay P · March 31, 2020

8 hours ago, Greydog said:

Hi Jay

Have a look at www.newtis.info you should find the test values and schedules for sensors there.I still think it is a failing loom insulation breaking down under load

Dave

Dave, when you say wiring loom is there any specific ones I should be looking at? Or isit a case of checking every single wire in the engine bay?

Jay P · March 31, 2020

5 hours ago, X5smw said:

Cam sensors can be found on the pulleys. I had an issue with one.

the sensor is located on the large pulley at the base of the engine. The rubber anti vibration art had perished and I could pull the pulley forward and backward on its shaft.
try all the pulleys by hand. It will be obvious if one has failed.

As greydog says, check the earth mounting on the engine and the connectors on the loom.
This might seem innocuous but plays an important part.

I actually forgot to tell the mechanic to check this. But it seems easy enough so I will have a look myself to see if that pulley is moving as you have described.

Jay P · April 1, 2020

Update:

Had an MOT done on the car just now as I am not in the exempt category 🙄

The guy said the emissions would have been a fail but after revving the engine harder it then passed - so at lower revs emissions aren't good.

Could this shed any light on any possible reasons for the misfire? Or isit unrelated?

Also something to note, the steering feels heavier than before since I have got the car back. Could this be related in anyway? Feels like not much power assist? Could it be a sensor of some sort that could cause car to misfire if steering isn't working properly?

Just a thought

As always thanks for the help so far really appreciate it and I'm learning a thing or two too whilst at it

Jay P · April 7, 2020

Update:

So on Sunday I decided to retrace the work that had been done by the mechanic when the spark plugs and coils were changed.

The first issue I noticed was that the clips on top of the coils were not properly fastened they were partially loose or partially wonky on one side where it is connected to the coil like it had come out of place. So I removed all the plugs and used electrical contact cleaner on all, sprayed some of the stuff on the wires and their housing and sprayed into where the pins were on the top of the coil. Also swapped all the coils around for good measure. And made sure the clips were properly fastened with the plugs in properly.

Best removed the two crank sensors which were a pain to get out, unplugged them, same process of electrical contact cleaner on the pins and plugs and reconnected up.

Next removed the plugs from the starter motors and sprayed into pins and plugs.

Removed various other sensors which I could reach without disconnecting major parts and cleaned with the spray on the pins and plugs.

Started the car up, was still sluggish...

Monday drove to work was still slightly sluggish but felt a little responsive. Got in the car at the end of the day, started it up to be met with an EML, hooked up my cheap code reader, two codes both related to throttle position sensor, the misfires were not showing this time. Cleared the codes. Removed my accelerator pedal and cleaned the sensor pins and plug with the same spray. Hooked it back up. Started the car and no codes.

Drove home and the car back to itself!! I couldn't believe it. When I got home I left the car to stand still for awhile and got back in for a drive round the block was still fine!

Today drove to work and it is still fine!

Moral of the long story?? Maybe check the sensors and pins and plugs and make sure they are crystal clean before getting expensive work done on the car next time! Also make sure the coil pack plugs on top are properly fastened with the clip in place and none being loose!

Another moral of the story? Make sure to check your mechanics work after him/her!!

I hope I'm not getting ahead of myself but I really do hope the issue is now fixed. The car feels great and is pulling strong.

Sorry for the essay but had to share the story in case anyone else has similar issues and what they should check.

Greydog · April 7, 2020

Way to go Jay

Don't worry about the essay the result counts

Dave

X5smw · April 7, 2020

Nice one jay!
well done and sorry for making you try every other sensor! 😂

Shaj 95 · July 21, 2020

Hey Jay P,

I have the same exact car like you - an E46 318ci.

I changed my engine 5 days ago. When I started it, I realized that 2 of the ignition coils were bad. I changed those coils. The engine stopped misfiring.

3 days ago, the check engine light came on. I was planning to go to the mechanic this mrn so I did not drive it during that time.

Turned on the car this morning, the check engine light was not there. Drove for about 80 miles and then the light returned.

Drove for a few miles attempting to get home as it was raining. On my way, the car lost power and stopped in the middle of the road. I put on my hazard lights looked around the engine bay for any lose wires - didn't find any. Disconnected the airflow metre plug and drove home - about 30 miles - with the check engine light on.

Tried to turn it on with the airflow metre connected but the engine turns over, cranks and starts then loses power and all the lights flash on the dashboard.

Going to run the codes tomorrow. But do you have any idea what may be the issue?