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Old 04-26-2017, 09:28 PM   #34
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Join Date: Jan 2017
Location: kalifornika

Originally Posted by whalepirot View Post
This is a big leak
Or not. Mulling that article, I was drawn to the low reading causes and wondered about late ignition and valve timing, neither of which I had touched.

After checking the spark strength with my tester, all looked good, eliminating poor plug wires and weak spark.

Attached the Snap-On timing light, read idle at 740-770 but the timing was off. Knowing the ECU controls it, I loosened the two small bolts and rotated the distributor back and forth, watching the vacuum drop, then increase, along with changed engine smoothness and RPM. Having tuned an old MB230 engine by ear, including syncing the two carbs, I maxed out the advance, which gave a better sound and smoothness, plus the most vacuum:17. Timing is 9-10 degrees, but I think it needs a bit more. Interesting is the ECU's adjustments to the widely varying distributor position, improving idle, to some degree.

The car has a more power and throttle response seems snappier. Well, sure. If the timing is too retarded, both will suffer. Now I am wondering if whomever replaced this engine, timed the belt close, but off, which would drop vacuum via late valve and spark timing.
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