E46 engine misfire

[Bryan Vjay]

Hi Guys, need your opinion, my car has been misfiring recently on & off.. exp when going slow.and its really bad now. I got it checked in 2 workshop and replaced all the plugs and ignition coils but still the same. MAF sensor replaced and fuel pump is OK. Did compression test and all 6 cylinder are good! what else? both bmw workshop cannot find what is the problem... do anyone had this problem? pls help :motz:

 

[jarance]

Have you done a diagnostic check? What is the error message?

 

[Bryan Vjay]

Error message saying misfire in cylinder 2 & 5, after awhile, all cylinder showing smooth running.. been few times like that

 

[jarance]

How much did you pay for the new ignition coils?

 

[Bryan Vjay]

Bought it from BA quite sometime ago, was keeping it. think around 150/pcs or 120/pcs cant remember.

 

[jarance]

Have you check rubber boot after the MAF for leakage? A loss of vacuum will sometime give erratic engine firing.

Check also your DISA while you at it.

 

[jarance]

BTW how do you know your fuel pump is working properly? Did you change it recently?

In addition, have you change your fuel filter and air filter recently?

There is a simple way to check the fuel pump.. you can use function #6 to verify the fuel pump.

 

[Bryan Vjay]

Bro Jarance yeah, that's what I told both the mechanic's as well that I suspect fuel pump. but both says no.. really confuse. before starting my car sometimes I hear the fuel pump noise like the petrol is being pumped. is that normal I dunno ... confused

 

[Bryan Vjay]

rubber boot after the MAF for leakage? I think this has been check. saw the mechanic pour lots of water in the engine while starting it :smokin: dunno why he did that to check what

 

[jarance]

Bro Jarance yeah, that's what I told both the mechanic's as well that I suspect fuel pump. but both says no.. really confuse. before starting my car sometimes I hear the fuel pump noise like the petrol is being pumped. is that normal I dunno ... confused

If you hear the pump just before starting, it means either there is leak somewhere. The fuel rail is suppose to hold the fuel pressure at 3.5 bar when the engine is stopped. Usually the leak is at the fuel pump outlet check valve. Petrol will be forced back through the check valve. You may have some problem starting in the morning after leaving the car overnight. (Like a few extra crank).

There is a simple way to check the fuel pump.
1. Press the odometer reset button and turn the ignition to position.
2. You will see a "Test Display". Press the odometer button many time until it come to "19.0"
3. Pause for a few seconds and then when the display change to "1.0", press the odometer button until it display "6.0"
4. The display will then display "123220". The first 3 digits show the fuel on the left tank and last 3 digits show the fuel on the right tank.

Note : Do this test when the tank is half full. If it full, the display will show 240330.

5. Start the engine and drive around. Observe the display. The first 3 digit on the left show gradually decrease to 000
and the right 3 digits should increase.

This test will prove the strength of the pump. If the pump is good, then the return fuel from the fuel regulator will return
back to the left fuel tank. it will pass thru the fuel jet pump and will suck the fuel from the left tank and transfer it to the
right tank where the fuel pump is located.

Recently, I have problem starting in the morning and also some error code on misfiring on #4 cylinder.

I did the above test and found that there always some fuel in the left tank at 1/4 tank. Sometime my car also stalled at 1/4 tank
but it is OK at full tank.

I bought a new fuel/sender from BA for RM350 and install it myself. So far in the car for a few weeks and the problem of hesitate
cold starting is no longer encounter. BTW, I also change my fuel filter as well.

 

[jarance]

rubber boot after the MAF for leakage? I think this has been check. saw the mechanic pour lots of water in the engine while starting it :smokin: dunno why he did that to check what

This is the first time I hear mechanic check for vacuum leak using water. :smokin:

 

[Bryan Vjay]

:stupid: I got the shock too when he checked using wafer... anyways checked fuel pump is working fine. I don't have any starting problems as well. always starts in 1st crank.. so now i'am not sure what's the culprit. left my car in workshop.. hopes he finds something

 

[anaksarawak]

Good infor and learned that fuel sender can caused a lot of headached and even power loss.

 

[Bryan Vjay]

Update... fuel lines or related no issue, checked the whole wiring also no issue.. now suspect ECU... could it be?

 

[jarance]

Update... fuel lines or related no issue, checked the whole wiring also no issue.. now suspect ECU... could it be?

what is fuel pressure at the fuel rail?

 

[Bryan Vjay]

Hi Jarance, special thanks to you. issue is solved :rock: but problem is Ignition Coil Harness, that's why even changing the ignition coils and plug didn't solve the problem. here I must respect Kuan from M power Ipoh, he just didn't give up for days solving it. he checked almost everything .... Chu seng penang couldn't and also my regular kl specialist couldn't find it (don't wanna mention his name summary car runs like a bimmer now !

 

[jarance]

Thank Bryan for the update. Just one more extra thing to look at when our ride have misfiring.

 

[bell]

how come the ignition coil can fail remain mystery..

 

[newbiebmw]

Connect scanner equipment and clear all history faults. You can fix problem.