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Discussion Starter · #1 ·
1999 Mk2 1.8, 105k

Recently shed its alternator belt which hit a number of items at the front of the engine and the old belt was wound behind both the crank pulley and the power steering pump pulley but the car run for a few days after that was sorted.

Broke down on the road and the AA towed it home it was a third party brake down truck not an AA man who could fix everything!!!!

New plugs in car a week before it stopped and would not start.

So battery charged and turning starter over the car is trying to start just catching then shakes and stops.

I have taken the plugs out and they are wet with petrol.

The MX5 should do two sparks on cylinders 2 and 3 and two sparks on cylinders 1 and 4 per two revs as it uses the wasted spark system. One coil pack for 1 and 4 and the other for 2 and 3 in the same metal frame.

I have all the plugs sitting on the rocker box to earth them and closed the garage door and the plug leads connected.

I turn it on the starter and I get one strong spark on 1 and 4 then two strong sparks on 2 and 3 then say a missed spark then 1 spark on 1 and 4 and two on 2 and 3.

Does anyone know if it is the crank sensor or the cam sensor on the Mk2 1.8 that triggers the spark.

From the above I assume

The connectors to the coil packs are working as 1 and 4 are sparking but no all the time.

The coil pack could be iffy.

The crank sensor or the timing blobs on the crank pulley are maybe causing the problems.

I have changed the MAF but that did not help.

Opinions please.
 

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5 FTW
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It almost sounds like there may be a tooth missing from the crank-wheel.
If you turn the crank by hand there should be four teeth.
 

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I have checked and all the four little bumps look fine on the crank pulley.

I also have pushed the crank sensor nearer to the crank pulley by loosening the 10mm bolt and adjusting the position of the crank sensor.

I was wondering if another crank sensor may help but in saying that why are the missing sparks so regular.

eddie
 
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