misfire

Need technical Q/A then you're in the right place

Moderator: martauto

User avatar
lowdub
E30 Zone Newbie
E30 Zone Newbie
Posts: 13
Joined: Sun Feb 20, 2011 11:00 pm

Post Mon Dec 01, 2014 1:48 am

hiya all,

my 325i has developed a very bad misfire, but it come and goes.

i started with changing my plugs- the old ones were very black..
next on my list i think would be the leads, cap n rotter. but i did ask a friend he was suggesting flue filter or a sensor.

any advise would be helpful

many thanks aaron
User avatar
Brianmoooore
E30 Zone Team Member
E30 Zone Team Member
Posts: 49360
Joined: Mon Jan 10, 2005 11:00 pm

Post Mon Dec 01, 2014 9:58 am

If this is a post facelift engine, start by measuring the resistance of the 'blue' coolant temp. sensor AT THE ECU PLUG, with the engine stone cold and then at full working temperature.
While measuring the hot resistance, reach under the inlet manifold and gently move the wiring to the round plug and socket fixed to the metalwork, which goes to the injectors. Do not move this wiring before taking the initial readings.
The resistance reading will gradually increase while you do this, but you are looking for sudden jumps.