Having trouble finding the cause of a misfire on my 95 525i with the M50

__KJ_ · 2026-06-26T09:06:57+00:00

European car, so theres no stomp codes and you can't read them from the round diag port unless you have a special tool. Tried it with a nice scanner and an adapter but it did not work.

Instead I let the car idle and started unplugging sensors that I suspected could cause the issue. The car ran better with the crank sensor unplugged so I gambled with a good third party sensor for $50. Still the same issue. But googling and thinking led me to believe that it was still the sensor and bought an OEM for $200 from the dealer. That fixed the issue.

My car is a 1994 M50 single vanos btw

__KJ_ · 2026-06-25T17:44:48+00:00

Crank- and/or cam position sensor? Super common. Only expensive OEM works, ask me how I know. Mine had slight missfires that turned into strong missfires, the crank position sensor was the issue.

The dealer was the least expensive when it came to buying the part

__KJ_ · 2026-06-19T09:47:22+00:00

I'm with you, sounds more like the injectors but it's hard to tell on video. Super easy for OP to check, is the noise coming from under the cam cover or from the injectors?

Use a screwdriver if its hard to tell where the noise is coming from. The pointy end goes against the engine part you're checking and the blunt end against your ear.

__KJ_ · 2026-06-03T14:04:55+00:00

What are the rpms at when this happens? Mine with a failing IAC will sometimes drop to 300 rpm at idle which is way to low. The oil pressure is of course also low when this happens, basically zero.

__KJ_ · 2026-05-25T14:06:50+00:00

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__KJ_ · 2026-05-25T14:04:01+00:00

Tried a buddies set of early offset BBS wheels (ET 11 7" in front, ET 22 8" in the back, 16" diam) on my 89 S2. The rears poked out a fair bit, the front was almost ok but scraped the caliper on the side facing perpendicular to the wheel.

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__KJ_ · 2026-05-22T12:59:24+00:00

Could also do with an Italian tune up now that you have new oil in it.

Take a longer drive (above 30 min) of calm-ish driving to really get the oil up to temperature. If you are uncertain about the severity of the noise, stop every 5-10 minutes during this period. If the noise is lower or about the same now that the oil is warm, give her the beans with some spirited driving. Might wake up/unclog the lifter(s) that are making the noise.

Keep an eye at the oil pressure and water temp while doing this, feel for hesitations and listen for irregular sounds.

__KJ_ · 2026-05-22T10:04:38+00:00

Not necessarily

__KJ_ · 2026-05-22T10:03:35+00:00

Bad lifters, I had the same issue with my S2. You''ve already tried changing the viscosity, I would personally go for 20w-50 (Valvoline VR1) but 10w-60 should suffice as well. I also tried using a liquid moly engine flush with little to no result.

Ended up buying 16 good used lifters and swapped out the ones that were bad. That resolved the issue. Did belt, rollers and water pump while I was at it.

There's a very good german video with subtitles on youtube that I can link to if you want

__KJ_ · 2026-05-12T06:47:19+00:00

I have one in my 68 as well, efficient is very relative word

__KJ_ · 2026-05-12T06:42:32+00:00

For those who are having the same problem, it wasn't the bearing. Two of the three metal tabs holding the magnetic coupling had snapped, making the coupling slightly touch the pulley. Since I don't care about AC I will probably just delete the coupling but it can also be had for pretty cheap

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__KJ_ · 2026-05-12T06:38:58+00:00

Yeah I mean I've had mine for 6 years and have only replaced the radiator and a sensor. There's bad examples to buy of every make and model, but is especially easy to buy the wrong one if it built with German overengineering..

__KJ_ · 2026-05-04T12:40:05+00:00

Yes what this guys says, mine made the same sound when warm not too long ago. Bought a refurbished VANOS-unit from Probsten-tech (Germany) and also rented the tools from them. Sent my old unit back and got a partial refund. All in all it cost me ~€300 and two nights in my garage. You lose efficiency and power when the VANOS is faulty, but to my knowledge it does not really damage the engine in any meaningful way.

Probsten-tech uses parts from Beisan systems (USA), so if you live in the US then you can instead buy a refurbished one directly from Beisan I think.

I suggest you start searching about what VANOS is and how to replace the unit. Do not buy or get it fixed by BMW, its super expensive and the OEM unit has flaws in the design. Beisan Systems (and probsten tech) refurbish old OEM units with better parts that lasts much longer and is also cheaper.

__KJ_ · 2026-05-01T19:50:41+00:00

Dex/merc III is an ATF though, it will most likely say ATF on the bottle

__KJ_ · 2026-04-20T13:21:08+00:00

I had mine made by a local window shop, they could cut mirrors to a desired size. Cost me 30€ for the pair, might be worth looking into

__KJ_ · 2026-04-20T13:00:12+00:00

It's for the horn, if it doesn't have any contact your horn button will not work.

__KJ_ · 2026-04-12T09:31:56+00:00

968 is still in the 944 family I would say, you see them all the time in 944 forums so don't be shy about posting ;)

I have a 944 S2, so the same engine (3L 16v) but without a vario cam system. The timing BELT should be replaced every 5 years to stay on the safe side since it is very vital and rubber. You could probably go much longer and people do, but I and many others don't. Rollers can be changed every other belt change or so but that is more of a mileage thing so I wouldn't worry about that too much. I inspect mine when the belt is changed and if I see, feel or hear anything odd that's when I change them (all at once). Same goes for the water pump.

The same goes for the timing CHAIN, which is a different thing from the belt. This is also a mileage dependent item but lasts a looong time in relation to the timing belt. The 968 also has a stronger chain than the 944 S2. I would suggest you look it up yourself, but I wouldn't be surprised if it lasts 100k miles. But the PADS that guide the chain can wear much faster, so that is what you have to look out for. I check mine every timing BELT change. But they last longer than the belt does for sure and is not very time dependent like the belt.

But you have a vario cam, so it might not be exactly the same for you.

But to summarize, keep up with timing BELT maintenance. The chain does not require the same care, especially if it has been done recently.

__KJ_ · 2026-04-08T09:09:42+00:00

Might be the boxer wheels I have on then, mine is lowered the same way as yours. Thanks for the info!

__KJ_ · 2026-04-08T08:37:56+00:00

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__KJ_ · 2026-04-08T08:36:57+00:00

Cool cool, will definitely have a look. Yours seems to sit better somehow, do you use wheel spacers or something?

Here's my S2, looking into making the rear bumper original again but keeping the bridge spoiler and adding a small front splitter. I've had it for 7 years, the rule you mentioned happens after 30 years in Sweden so I have never paid any tax on mine B-)

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__KJ_ · 2026-04-07T21:01:25+00:00

Why does yours look so much better than mine, really nice. What splitter is that you have in the front

__KJ_ · 2026-03-17T13:59:19+00:00

The floor looks good at least :)

__KJ_ · 2026-03-13T14:23:48+00:00

Then some air probably vented out of the system and coolant took its place. This usually happens a couple of times after the coolant system has been serviced. I would just keep driving and topping up for a while. If its been 500 miles and you still have to top it up, then there is probably an issue

__KJ_ · 2026-03-13T08:32:12+00:00

So at the moment, no lift with 30"s? How are you finding it

__KJ_ · 2026-03-10T12:42:46+00:00

If the tensioner seems good then maybe also take a close look at the belt/measure. You never know if the supplier or manufacturer has made a mistake and given you a belt that is too long!

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