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I recently had fully lined up a good E30 Alpina in the UK to import, and a donor car here for parts or shell. Then my father passed away unexpectedly and with that upheaval the big project wasn't a good idea, so I grabbed a local 1987 M325, with a few things that need ironing out. Stumbling idle. The car idles at a steady speed wherever set, but has a distinct stumble/misfire. No issues apparent at speed but it may be masked at those revs. Idles as if it has a lumpy cam. Valve clearances have been done Spark plugs replaced dizzy cap checked/cleaned- was new 10,000km ago injectors were apparently serviced and found to be clogged or grubby, fuel filter has been changed, presumable after that. All injectors are actuating. Vacuum leaks checked to a simple level, intake boot appears new as do various other parts. AFM has no flat spots and tests with steadily increasing resistance. Spark is apparent at all plugs Car has the two crank sensors on the bellhousing, an unexpected hall sensor on the harmonic balancer with cable up to the OBD plug(smooth rimmed balancer, where is the sensor picking a signal from?) and a sensor on one spark plug lead plugged to nowhere, I presume for facelift cars with newer motronic. That is really my core interest. The metallic rattle from under the car could be an undisclosed lightened flywheel, a crappy input shaft bearing, throwout bearing or clutch springs, or simply the effect of a misfiring idle on those components. Am happy to have them all replaced. Could the ECU (Motronic 1.0) cause this, even though the car basically runs well and there is no major misfire? Could the coil cause it? I'd not imagine it could being as it generally gets spark to where it needs to go. Thanks Nathan

Hi All, Nice to e-meet you all, I'll soon be (hopefully) getting hold of a F80, M3 so pics to come once I've got the car. I'd like to think I've moved up the BMW ranks with my very first car being a 316i which was followed by a 318i and a 323i before moving away from BMW briefly.

looking good buddy! love your car !

hey bud. Check your your hoses for vacuum leaks, check also the resistance of the crank and reference sensors on the bellhousing, these can give a stumbling idle. Also check the resistance on your ignition coil. I have had a few of these play up. Other things to check would be your idle control valve, take it out, clean it, make sure it's operating correctly with the correct resistance etc and check the intake house from your throttle body for cracks. Also the little pipes that come out the side of the throttle body need to be tightly fitted as they tend to have the knurled surfaces wear where they fit into the throttle body causing leaks. The sensor on the harmonic balancer is for the diagnostic port at the top of the engine and doesn't really do anything as far as connecting to the ECU. The plugs just go straight to the diagnostic port. Other things to check is pull out the oil cap while running and see how much crank case pressure you have, worn rings etc can make it idle funny if you're low on compression or there is blow by. Happy to check it out for you if you want to swing by my shop sometime in Glenfield. Love me a tech 1! I have one myself. Cheers 02102916373 SJ

Small world, I know the new owner! She says it drives awesome.

Hi Dan would like the brake lines, PCV hose thingee, the bulbs and misc stuff? Thanks

Hey Dude I will take the Mickey Mouse and oil filter please

Thought I’d update this, car is pretty much how I want it now so no real need to change much, especially with having picked up an e30 as a new project (there’s a thread for it on here too if you’re interested). car drives great, works perfectly, couldn’t be happier with it, feels special to drive. Took it out for a summers evening drive and got some photos.

I think we all knew it was something along those lines. Still dont agree with the deleting on the thread though.