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Ignition advanced, can't adjust, part II 700 1986

posted by  dylant on  Wed Apr 9 12:12 CST 2003
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last visit: Tue Oct 16 15:08 CST 2001
[RELATED]

I mentioned that part of the harness in my first post- everything checks out, and about all that's left to do as far as testing this area would be to energize that trigger at the ignition ECU and verify that the ignition *does* advance. If not, I'd suspect a bad ECU.

Here's where it gets fun-

I replaced the FPR, O2 sensor seems to register slightly lower voltages, still a little high. I suppose if the burn isn't right with the timing so far advanced then I would expect to see a "rich" exhaust stream.

Out of frustration I pulled the two bolts securing the distributor and limiting its adjustment- I was able to bring the timing to 12 degrees BTDC and decided to take it for a short trip. Turned out to be very short- the car had no power off boost. This was a more magnified version of what I had before, not much power off boost.

So I drove the car home and yanked the knock sensor- for some reason I had two more sitting around, same Volvo PN. They all test the same- 300K ohm, and one looks like it has never been used. I checked the harness- ground is good, and the 'hot' side of the sensor coax shows totally open to harness and chassis ground.

I put the new one in just to double check.

I'm begining to consider replacing the crank pulley & timing belt, but will test for separation as per VolvoSteel's advice. After that, I suppose I'll throw an O2 sensor at it.

Two strange thoughts-

- Could a bad O2/rich mixture/something-like-that cause the Fuel ECU to tell the Ignition ECU to advance the timing? I've read that the Coolant Temperature Sensor, connected to the Fuel ECU, will tell the ignition to advance based on cold coolant temperatures. Is the O2 system that smart too?

- The past owner mentioned they had the mechanic "advance" the timing. Could the mechanic have reversed the distributor in the head intentionally? I've read that when replacing the distributor you can install it 180 degrees out of whack and then have no luck getting the timing right. Any way to verify this distributor is in right by pulling the distributor?

Thanks for all the help-
-Dylan





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