Etwenty1 45 Report post Posted June 15, 2015 hi I have an 89 535i project car that has a bad miss. Misses at idle and under throttle. Engine has new head gasket, no apparent vacuum leaks, new cap and rotor. I hooked up my timing light wondering if I could isolate it to a lead and found the miss shows up on the lead from the coil to the cap. Can anyone advise if this means the coil is the problem? Or does the signal originate from the sensor on the crank. Quote Share this post Link to post Share on other sites
Auzeras 28 Report post Posted June 21, 2015 (edited) If you're ever in Wellington feel free to borrow my coil to test, not sure when I'll be up north otherwise I'd offer to bring it with me next time work throws me on the road. Easiest way to test is by trying to find a local one to borrow. If you get really stuck try asking on the US BMW forums - there are a lot of guys there with a heck of a lot of knowledge on the M30 there. Crank position sensor only affects the fuel delivery if I recall correctly, when were the coil/leads/plugs last replaced? In my E32 they're OEM (eg 27 years old) so if yours are the same I'd say replacing them can't hurt at the very least. You've probably been told but with an M30 I *highly* recommend pulling the valve cover and checking the oil spray bar bolts and if possibly safety wiring them in. Also a good time to pull the plugs and see if you can see any difference in condition of them & adjust the valves. The M30 is pretty particular about some things. It won't clear up a misfire but I've heard countless discussions on the US E32 forums about how little tweaks make huge differences to the smooth running of the M30. Also check for oil leaks from the valve cover, often oil runs down into the plug wells and causes misfires. If you replace the plugs stick with OEM Bosch coppers, they run a bit rough with the platinum ones so I'm told. Edited June 21, 2015 by Auzeras Quote Share this post Link to post Share on other sites
BM WORLD 1275 Report post Posted June 21, 2015 coils hardly ever fail . crank sensors are very important , does everything , but don't often fail on these . the mount they mount to can come loose or break sometimes. misses are normally related to spark plug leads(high resistance) ,spark plugs, dizzy cap , rotor etc so check all those first . then ecu issues , but not that common . worn out afm .will causes fuelling issues , rough running , bad idle etc . fuel pressure regs sometimes fail leak fuel down the vac hose. Quote Share this post Link to post Share on other sites
Etwenty1 45 Report post Posted June 21, 2015 Thanks Mac, i swapped out the coil, king lead with no joy then unplugged and reseated the plug on the ECU and it seems to be running fine, the clear misfire is gone anyway. Just have the original overheating issue to deal with. I have put in new larger radiator - it had some UK cold climate version. The overflow hose to the expansion tank was blocked, there is a pin hole in the top hose and the viscous fan is easy to stop when fully warm. It sits at 12' o clock for a while but then slowly creeps over. Then its onto the squeaky cabin fan.... Quote Share this post Link to post Share on other sites
Etwenty1 45 Report post Posted June 21, 2015 Thanks Brent, have also noticed that disconnecting the ICV make no difference to idle, however it idles fine. Quote Share this post Link to post Share on other sites
BM WORLD 1275 Report post Posted June 21, 2015 change the viscous and that top hose , they must be working properly or you will have over heating issues Quote Share this post Link to post Share on other sites
Auzeras 28 Report post Posted June 23, 2015 (edited) Does the aux fan come on? Might have to change out the temp sensor for the DME. It's normal for the temp to rise a bit when idling with low airflow (eg parked). If the fans don't come on: Test: On the side of the radiator there's a thermostat for the aux fan, unplug it and Jump the centre pin (brown/black wire) to the each of the two outer pins one at a time. The fan should run Hi and Lo. If it doesn't run check - Fuses, Relays, Ballast Resistor If it does run when jumped replace the thermostat/temp guage on the rad. See here for detail of aux fan troubleshooting http://www.nmia.com/~dgnrg/page_20.htm Replace the viscous clutch though, I'm living with mine being a little off at the moment as with the colder weather it barely even triggers the aux fan. Edited June 23, 2015 by Auzeras Quote Share this post Link to post Share on other sites
Etwenty1 45 Report post Posted June 23, 2015 No aux fan as far as I know unless there is a pusher hidden in front of the ac thingy. Thanks for link. My replacement fan clutch and hose have already turned up from bmw world cheers Brent so will be fitting those asap. Quote Share this post Link to post Share on other sites
