S50 Misfiring problem, **Update with pics**

[kalib0y]

Hey Guys,

So Ive searched my eyes sore and now I need your help.

I have an s50 swapped into my E30 and its been running like a champ for a few months now. The motor is basically stock with a lightweight flywheel, Dinan BBTB, rebuilt head with updated lifters, raceland headers. I track it often and just did a upgrade to Euro 3.5 HFM, 21# injectors, and TRM tune with bimmerworld boot 2 days ago.

SO yesterday, I am driving regularly as the engine is warming up and its starts to misfire.

It misfires during idle and while under load, down on power. The idle is steady and is not erratic at all. No smoke coming out of the exhaust, or anything odd in the coolant. No temperature problems. No fault codes.

I immediately thought that maybe the injectors went bad since I bought them used so I bought new injectors, installed them...still same problem. I changed the plugs, still same problem. And the same result after I cleaned the MAF. I am now going to play with different OEM coil packs tomorrow and I hope just like the other times that it may fix the problem. Sounds like the misfiring is most audible around cylinder 5 and 6.

Now I need to ask you experts. Could I have somehow damaged a valve on track (I hope not)? It drove fine the whole track day, the 2hr trip home, and for 2 days after. What else could it be?



Cliffs:
-I have an s50 swapped e30 that I track often
-I developed a misfire 2 days after I upgraded to Euro hfm, 21# injectors, and TRM tune
-Misfires during idle and under load
-sounds like a go kart now and is down on power
-Sounds like the misfiring is most audible around cylinder 5 and 6.
-Idles perfectly, no temp issues, no smoke, coolant looks fine, no fault codes
-I changed to brand new injectors, spark plugs, and cleaned MAF
-Going to play with different coil packs soon
-Need your input

Thanks guys

[e46s54dr]

It might very well be a dead coil or boot. Try and isolate which cylinder or cylinders the misfire is coming from. When do do find the dead cylinder(s), try swapping the coils around to see if the misfire moves to the corresponding coil pack. Also, when you cleaned the maf sensor, did you check to see if the little hair was still there and not broken? My e46 had the same problem when the hair in the maf somehow broke.

[dsobering47]

Before you swap coils, just unplug them one at a time and take note of the idle. If the idle doesn't change after unplugging one of them, then you have found your bad coil/cylinder. You can then swap coils from there to pinpoint which one.

[nrubenstein]

If you have access to a kitchen thermometer, measure the temperature of each header. That'll tell you which cylinder is down if you've got a consistent issue.

[Beej '86 325es]

I'm having a nearly identical issue around cylinder 6. From the reading I've done, I'm suspecting a bad coil pack since that's one of the very few things on the engine that's used. I've got spark though.
Is it possible to get a weak spark through the packs or are they just working/not-working?

[Adrian_Visser]

Does your injector harness rail have the locking clips installed on the connectors to the injectors?

I had an intermittent dead # 6 cylinder shortly after my first start up and it turned out that the injector connector for the #6 injector wasn't making contact, I had to go steal the clips from my m20's injectors. Just something else to check. Otherwise I'd suspect a bad coil.

[kalib0y]

Well I did some coil swapping and found that i got no change in idle on cylinders 4 and 5 so I moved the coils around and 4 and 5 again are nit firing. So i get a lil weary and plug in the compression tester. Mind you I did this while the car is cold so the number will be very low but its obvious that even if I did the test with the car at temp it would yield the same result but with higher numbers of course.

1:165
2:160
3:165
4:40
5:30
6:165

Result! now I remember that I thought i got away with a slight MONEYSHIFT at the track, bad shifting technique, and was going WOT down the straight and went 3-2 instead of 3-4. She drove home fine as she did for the next 2 days. I thought I dodged a bullet. I guess I didn't...

well at least I know the injectors, coils, and plugs are good...

[ACHTUNG]

Result! now I remember that I thought i got away with a slight MONEYSHIFT at the track, bad shifting technique, and was going WOT down the straight and went 3-2 instead of 3-4. She drove home fine as she did for the next 2 days. I thought I dodged a bullet. I guess I didn't...

damn. that sucks.

[nrubenstein]

Oh well. It's either that or a head gasket. That doesn't really change what you've got to do, though.

[giantkeeper]

man, that blows!

[jrdeamicis]

Leak down test it before you go any farther. Then do a wet test. Then tear the head off. and do the appropriate work.

[kalib0y]

Okay, well I learned a neat trick, If you hold the throttle open while you turn off the car, you can hear a whoosh of air blow past the valves if they are bent so now this is the plan of action

-rip out head
-service head pressure test
-cosmetic head gasket to bring it back to OEM compression
-ARP studs
-fererra 1mm oversized valves with updated retainers and springs
-install everything back

If you are wondering why, the car may see some boost in its future :)

be ready for Willow springs, Big willow on the 12th

[azael325i]

That a boy... Boosting is fun ;)

[kalib0y]

yeah well to me it isnt lol, reliability is. My e36 turbo widebody was a real PITA to maintain. There comes a point when you modded it so much that its nothing but problems. I was constantly finding oil leaks.

This time Im going for reliable power and not trying to set any records haha. My E36 put down 542whp right before I sold it btw

[azael325i]

This is my 1st turbo car and so far no oil leaks yet but I'm sure I'll get one later down the road. cross your fingers lol