Misfire code on all 6 cylinders

Hello all.

I'm looking for some guidance here before I go too much further on this project. I have done quite a bit of searching but I don't think the answers I've found really relate to my specific problem. Hopefully one of the experts here can shed some light. I purchased this car about a month ago and I've been fixing lots of little things on it and learning about it as I go but a lot of the age of specific parts are unknown to me.

The car: 1999 M3 S52 with OBD1 intake manifold and TMS/Conforti stage 4+ (installed 25k miles ago during motor rebuild)
The problem: Check engine light. Peake code scanner comes up with 6 codes (misfire on each cyl)
What I've tried so far: Replaced spark plugs (tiny bit of oil on the threads of plugs 2 and 5 but not enough to be concerned about), replaced plug boots on 3 and 4 (cracked near the bottom, inspected other 4, they're fine), Cleaned up the battery ground (this was corroded and actually the car ran better once fixing, but the codes still came back).

The car runs very smoothly and I do not detect any misfires while driving it. It DOES idle a little roughly sometimes but I am not sure if maybe that is just the lumpy cam.

Thanks in advance.

I just saw this thread, so sorry no one has replied yet.

Have you checked the coil packs? I know it's tough if all 6 are giving codes, but try to find a pack you KNOW is good and swap it out. If you were in the Bay Area I'd help out, but I can't drive to So Cal for that :P

Originally Posted by petriej

I just saw this thread, so sorry no one has replied yet.

Have you checked the coil packs? I know it's tough if all 6 are giving codes, but try to find a pack you KNOW is good and swap it out. If you were in the Bay Area I'd help out, but I can't drive to So Cal for that :P

Thanks for the reply.

I have not checked the coil packs. It seemed unlikely to me that all 6 would be bad but then again the P/O possibly could have just ignored them for a while. Then again the car runs remarkably well for having 6 bad coils. Also I think the packs are new from the rebuild 25k miles ago. I will try checking the paperwork to verify.

But I'm definitely not ready to rule anything out. I'll see if I can find a known good one to try.

Well, I think (think) the misfire codes come from a sensor that reads the amount of current draw from the spark plugs. It's a neat way of determining if the cylinder fired properly.

So start with the basics:

You need air/gas mix and a spark, all at the right time, otherwise you get a miss. If all 6 are missing but the car seems to run fine, it might be a timing issue. I hope not, because that can get expensive to fix

At the risk of blowing something up, how well does it run when you bring the RPMs up past 4k?

That's when VANOS is really going, so any timing issues would be exaggerated.

The car has been up to 7k Rpms many times with no problems. Very smooth and lots of power.

The p.o. Says the CEL is due to the euro spec high flow MAF. Could this be the case?

If it ran rough, I would have suggested vacuum leak.

Originally Posted by mujjuman

If it ran rough, I would have suggested vacuum leak.

I have looked for a vacuum leak (carb cleaner test) and didn't find anything. It runs slightly rough at idle (650 rpm) but if I touch the throttle at all it smooths out.