Picked up an 325es last week with an m50tub25 in it. the guy who I bought it from installed it and seemed pretty informative but told me it was misfiring cylinder #4 he needed to get rid of it before winter as he has a baby on the way and 2 other project bimmers and not enough room in the garage.. I wanted a project e30/weekend driver and got a great price on it (rust free!!!).
Heres the thing, it misfires, it idles rough, it hesitates, hiccups and rpms drop really slowly. I spent a good hunk of the weekend diagnosing and the biggest problem is I think it's misfiring on several cylinders intermittently… I agree cylinder #4 seems to be the most often, but pulling any plug on any cylinder shows a drop in rpm… I'm not convinced its only #4
heres the specs and tests I've performed so far:
spark test: all cylinders sparking
spark plugs: replaced with the OEM .032 NGK's
Coil in line tester: all coils working, if I swap #4coil to a different one, #4 cylinder still seems the most obvious
Compression Test: all cylinders 180psi +
Fuel injector noid test: all fuel injectors have steady/smooth signal
Swapped fuel injector #4: no difference
no vacuum leaks confirmed, I can hear a light hiss if i hold my ear up to the manifold (actually near #4). I've sprayed starting fluid all over this area with absolutely no proof that theres actually a leak. (another m50 guy told me this hiss maybe normal, can anyone confirm this)….
if its not the intake manifold gasket I'm down to it being very electrical, like a dead DME or a bad camshaft/crankshaft sensor.. can anyone confirm a legitimate way of testing these? or any other ideas, things I haven't tried?
below is a picture of my plugs (you'll notice number 4 is the only one without black soot, I'm thinking that supports my gasket idea if its just being leaned out)
Heres the thing, it misfires, it idles rough, it hesitates, hiccups and rpms drop really slowly. I spent a good hunk of the weekend diagnosing and the biggest problem is I think it's misfiring on several cylinders intermittently… I agree cylinder #4 seems to be the most often, but pulling any plug on any cylinder shows a drop in rpm… I'm not convinced its only #4
heres the specs and tests I've performed so far:
spark test: all cylinders sparking
spark plugs: replaced with the OEM .032 NGK's
Coil in line tester: all coils working, if I swap #4coil to a different one, #4 cylinder still seems the most obvious
Compression Test: all cylinders 180psi +
Fuel injector noid test: all fuel injectors have steady/smooth signal
Swapped fuel injector #4: no difference
no vacuum leaks confirmed, I can hear a light hiss if i hold my ear up to the manifold (actually near #4). I've sprayed starting fluid all over this area with absolutely no proof that theres actually a leak. (another m50 guy told me this hiss maybe normal, can anyone confirm this)….
if its not the intake manifold gasket I'm down to it being very electrical, like a dead DME or a bad camshaft/crankshaft sensor.. can anyone confirm a legitimate way of testing these? or any other ideas, things I haven't tried?
below is a picture of my plugs (you'll notice number 4 is the only one without black soot, I'm thinking that supports my gasket idea if its just being leaned out)
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