1997 m3 Cold start engine miss

[97byzanzm3]

As the title states, my m3 is missing on several cylinders when it has been sitting for a few hours. I have not owned this car long and the previous owner doesn't seem to have done a lot of maintenance on the car. The car slowly picks up cylinders and starts to smooth out if I let it idle. It normally takes about 3 mins for the whole process to be over and the car to be running correctly. I have pulled codes and the only one I get is code 41 which is strange because the sensor is brand new. Does anyone know what might cause an issue like this? Any help would be great.

[328 Power 04]

Put an original BMW camshaft position sensor in first. No aftermarket.

Then look at spark plugs, coils, and possibly injectors.

[97byzanzm3]

Ok. The camshaft sensor I put in it was a new fae that a friend had from his last car so I'll order an oem. The injectors were just cleaned and flow tested so I'm not 100% sure that will solve anything. I've heard of coils getting hot and then stop working because of the higher resistance but never the other way around

[bmwdirtracer]

Coolant leaking into those cylinders?

[328 Power 04]

I was way more optimistic than that. But it makes sense, and you probably have your fair share of cases.

[97byzanzm3]

I guess that could be but it doesn't seem to use any and I don't have any smoke while it's missing. Also, wouldn't that cause it to hydro lock?

[bmwdirtracer]

If you have no other symptoms of coolant system trouble, you can forget what I just said. Yes, there would be heavy vapor. Most often, it's a small drip / trickle, enough to seriously foul combustion for a half a minute, but way short of a hydrolock. I do, in fact, have an M54 coming apart for this right now, and generally do several a year. Coolant / combustion interchange is the most common BMW head gasket failure.

Spark plugs are fairly recent NGK BKR6 EK or EQUP? Coils are absolutely suspect, too.

A good scanner can usually count misfires on each cylinder.

Also, you indicate that this clears up if you let it idle a few minutes -- What if you just go and drive it? At the very least, putting it under some load while it's misfiring might make a code set that will point you to which cylinder(s) is the trouble.

[97byzanzm3]

I'm not sure how old the plugs in it are but they are definitely on my list of stuff to replace. I don't think driving it while it's missing would work since its idling around 400 rpm and any throttle input seems to try and kill it. I drove it around yesterday for about 8 miles and parked it. When I started it this morning, it had a very slight miss that smoothed out much quicker than before. Is it possible since it Sat so long that maybe vanos is sticking due to old oil and lack of use?

[bmwdirtracer]

How old is the gasoline in the car?

[97byzanzm3]

When I first got the car it hadn't ran in probably 2 years so the pump was toast. When I replaced the pump, I also pulled as much of the varnish from the tank as I could, then I put about 5 gallons of premium It which is probably about 2 months old at this point. I did put another 10 gallons of fresh fuel in it yesterday when I drove it though so maybe that helped it?

[bmwdirtracer]

Quite likely.

Certainly, you should pull a spark plug or two, see what's there, and what they look like. Sometimes, people who don't know BMWs put Autolite or some other lawnmower sparkplugs in. You want NGK BKR6 EK or BKR6 EQUP. (No Bosch +4's either !)

And then, assuming that everything's acting fairly normal, cooling system and oil full, I'd say it's time to go drive the car hard for five minutes. Find an empty road, and scream it to ~6000 rpm, flat out, through at least three gears. If all remains fine, do another hard rip through three gears.

German cars like Italian tune-ups.....

[97byzanzm3]

Ok. I will double check fluid levels and give that a try. I'll report back with results in a few days. Thank you for all the info

[97byzanzm3]

So I took the car out and drove it hard for a bit. I let it sit overnight and it still stumbled a bit this morning when I started it. It took a second of cranking before it caught, idled up, stumbled and recovered. What I noticed when It turned over is that it sounds like it had no compression on 1 hole. Is it possible maybe base timing jumped a tooth and keeps a valve open during a cold start compression stroke? Then once it starts the vanos system takes over and adjusts the cam timing? The car still has a cam sensor code on cold starts that goes out if I drive the car long enough.

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The car has 130k miles

[bmwdirtracer]

The timing didn't jump, but it's certainly possible that you have a vanos issue which is caused by oil sludge, and aggravated by cold oil. However, if this is a single-cylinder issue, I'd certainly recommend a leak down test, a set of plugs, and watching live misfire data to see which cylinder is giving you a problem. There are VERY MANY possibilities, so more info is needed.

[97byzanzm3]

When the car was originally missing on multiple cylinders, it sounded like multiple holes lacked compression, now it's just this one and it's not every time I cold start it.

- - - Updated - - -

I will continue to drive it this week and see if anyone at work has a scan tool that will communicate with this car. I had a friend suggest a crank sensor aswell. He said it's possible that maybe the crank sensor isn t showing the ecm what it wants to see and it's thinking cam timing is off and throwing a light for it. Idk how realistic that is so I figured I would post it up and get some feedback on it

[Mless5]

If you get a code for CPS, you might as well start with that and like others mentioned, make sure it is OEM.
And hello from another Byzanz owner