E30 it stops, it goes, it stops... revisited

[Nick Brearley <nick@xxxxxxxxxxxxxxxxxx>]

A few weeks ago I asked a question about an 86 E30 325i which lost it's
ignition spark without warning. The engine would stop at any time during the
day then restart 75 minutes later (almost to the minute) and carry on as if
nothing had happened. A couple of digesters were good enough to point out
that sometimes this problem was linked to a faulty main relay. So, in went a
new relay and for a couple of weeks things were fine.

Then back again to the unscheduled stops. Moving up the cost chain the coil
was the next to be replaced - still no solution. Multimeter time, after
going through the ECU tests in Bentley everything checked out OK. Even
though the car is a 325i, being a UK spec 86 model the electrics have more
in common with the US 325e - 35 point Motronic unit and Reference and Engine
speed sensors.

That just left the ECU so I picked up a reconditioned unit, carried it
around for a few days until the next stoppage and fitted it straight away.
Great.. engine restarts immediately, no 75 minute wait. Problem solved, or
so I thought.

Two weeks later I lose nearly four hours waiting on the motorway hard
shoulder for that **** car to complete a 300 mile round trip with three
unscheduled stops. That left one drastic remedy so I went out and bought an
E36 325i. 

Before I put the E30 into cryogenic storage to wait for science to find a
cure any suggestions about the reason would be gratefully received. To
recap, the engine loses spark after it has been running for a while, it will
always start from cold. There is 12 volts at the coil but nothing reaching
the distributor. After 75 mins everything is fine again. I figure the
reconditioned ECU is the culprit but before an amateur goes into the ring
with people who earn their living with scopes and meters he needs to be very
sure of his facts...

Thanks for any info.

Nick Brearley

86 E30 325i 441k (I'd been hoping for 500k and an honourable retirement)
93 E36 325i 59k

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