Intermittant Misfire on Idle - Hot and Cold

Hi there,

I have a 1997 318is coupe, M44, mileage 102,000 Uk standard spec. It recently started to misfire on idle and power was noticeably less when driving. I replaced the plugs, plug leads, and when that didnt really help I replaced the coil pack. This cured the misfire in that it does it a lot less and not as severe as before. It has recently passed its MOT with flying colours and had a bmw dealer oil service. I have checked the hoses and connections and everything seems tight and secure. The car has a full service history as well.

But it still misfires and im asking if anyone with a lot more knowledge could assist me further. I want my baby back the way it was before! The annoying thing is that its now intermittant. You can start the car and it will not misfire at all. Other times it does its misfire thing. Its hard for me to say whether or not its misfiring during driving as theres not really any noticable power loss, but there may be. Dont know which cylinder it is, but suspect that its only one of them, as the power loss would a lot more noticeable when driving. Im not getting any warning lights on the dashboard or anything. Could it be one of the sensors? Or injectors? Im stumped at what to do next.

Any help you guys can suggest is appreciated.

Richie

Richie,

I also have a 318is with almost the same mileage, it has the same problem and I too changed the plugs then the leads and I have had a new ignition pack with just over a week.
Like you the problem seems not as bad but I am still getting misfire codes and the car is not back to its best.

Did you ever find out what the cause was, my replacement of parts is getting too expensive to be guessing what to change next.

glen

I had my camshaft position sensor changed recently, which cleared up an intermittment rough idle, as well as a loss of power issue. Apparently the CPS issue is a known issue with the M44 engines. Try replacing that part (it's about $100 US) and see if it helps?

Originally Posted by glen

Richie,

I also have a 318is with almost the same mileage, it has the same problem and I too changed the plugs then the leads and I have had a new ignition pack with just over a week.
Like you the problem seems not as bad but I am still getting misfire codes and the car is not back to its best.

Did you ever find out what the cause was, my replacement of parts is getting too expensive to be guessing what to change next.

glen

Glen,

Wow ive just come across this thread after so long, so apologies that I was not able to come back here sooner. What finally cured it was, in addition to the other fixes, was a replacement of the fuel filter (located in the underbelly on the car and is located around the passenger seat area - right hand drive). The part cost only £10 and basically finally removed the misfire issue. The old filter had not been replaced since manufacture, I suspect, and it was full of fuel residue and sludge. The car ran like new after that - and I still own the car. Hope you also got your issue sorted.

Richie

i have the exact same bimmer (m44 engine 318 is canada spec 1997) and i've been driving with this issue for almost a year. It passed emission testing for some strange reason but like the thread maker no power issues, just misfires randomly at idle.

I do have a check engine light, but mine goes away sometimes... then when the car misfires its back again.


ok if i change the fuel filter and the problem goes away im going to call u guys god ahah but im highly doubting it

Your pistons may be carbonized.

Originally Posted by tGunter

Your pistons may be carbonized.

would you recommend one of those oil change flushes (Like adding an additive like MOA) before the oil change to get rid of the carbon deposits?

update: I pulled out the plugs I installed 10,000 km ago, seems that cylinder 1 (front of the engine) has some excess carbon since the metal part where your spark plug wrench wraps around, has a light yellow of coating which can be easily wiped off. Looking into the cylinders 1 and 2 (from top view down) I saw that the rings were coated in some black (too rich?) but cylinders 3 and 4 were clean. But the 2nd spark plug did not have the same coating so I was wondering if its just 1 cylinder that's giving me a problem and not two? I checked my wires and they were not torn or anything so I'm just curious if the fuel filter trick does not work (I still need to get a low profile jack) I'm wondering if I should just fix the camshaft position sensor and bite the bullet at the dealership. Does anyone have access to that TSB for m44 engines? I was wondering if there was a VIN range for the vehicles affected?

Hm... i want that smooth idle back but I don't notice any power problems, one suggested to clean your IDLE control Valve but that's only if your RPMS are swining when your at a dead stop, mine stays the same but you can feel a roughness and misfiring.

Do you suppose oxygen sensors can play a role in this? The m44 engine has two to replace right?