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setting mixture with dwell meter[200/1988] posted by Scott Massey on
Wednesday, 16 December 1998, at 8:26 a.m.
I flunked VA emissions yesterday with high NO. I am using BG44k for the next tank. I also changed the thermostat to the stock 87 degree C. It had a 93 degree C?
I would like to check all base settings before I go for a second try. The timing is good along with all other tune up settings.
This car was my brothers and he had a new air mass meter installed last summer (bad preheat flap). The work was done at a gas station and I feel they did not set up the new AMM properly. On my 85 745t I used a dwell meter at the test port and adjusted the AMM so the meter moved between 30-70.
This 88 240 has a blue connector by the PS fluid with a pink wire and a wire with a stripe. I used the wire with the stripe and got a constant 70 on the dwell. I disconnected the O2 sensor (with engine running) and still got 70 on the dwell? Turning the AMM adjustment does nothing. What am I doing wrong??
I am hooking the + on the dwell to the test port and the - to ground. Is this correct?
This car also has a black 2 prong connector near the firewall. The connectors are female and much smaller than the blue plug at the PS. What is this black plug used for?
If this procedure is outlined in the Bentley manual let me know. I need to buy it anyway. It was not available when I owned my last Volvo.
Thanks in advance.
Scott
Re: setting mixture with dwell meter[200/1988] posted by vladimir kordic on
Wednesday, 16 December 1998, at 5:39 p.m.
Scott,
Assuming your ignition timing, idle and 02 sensor are all within specs, here's how Bosch advised me to adjust my AMM. It isn't described in Bentley this way, but my O2 sensor/AMM are properly calibrated and my emmision levels are extremely low for that year (or so I've been told). You'll need a Digital Multimeter (DMM).
Make sure engine is fully warm, then shut off.
With 02 sensor UNPLUGGED, connect meter to single signal wire off sensor to read low DC range voltage.
Slowly turn adjusting screw at AMM either clockwise or counterclockwise to bring voltage in the .3-.8v range. Signal should fluctuate. And THAT'S IT!
Now on my 84 clockwise is richer, cc is leaner. Yours may be different. Bentley has it the opposite, so I'm not sure.
The resistence value on MY LH2 AMM for optimal mix is 304ohms. Yours will no doubt be different.
Good luck.
--
vladimir
Re: setting mixture with dwell meter[200/1988] posted by Scott Massey on
Thursday, 17 December 1998, at 8:19 a.m.
Thanks for all the help. I figured out what I was doing wrong. I was hooking up the dwell to the wrong wire. The correct wire is the pink wire. My dwell now cycles at the lean end of the setting.
I tried the O2 method by using my Fluke multi-meter. The cycle range was 2-3 turns of the screw. Using a dwell on the pink wire the cycle range is less than 1/2 turn of the screw.
We in VA have the new dyno emissions test. It simulates actual driving and is very hard to pass. The old tail pipe idle test was very easy to pass. You did not even need a cat if you were set a little lean. Your car must run like new to pass the new test.
Scott
Re: setting mixture with dwell meter[200/1988] posted by vladimir kordic on
Thursday, 17 December 1998, at 9:29 a.m.
If I read you correctly, it sounds like the dwell method is a more accurate form of adjustment.
What I think you're saying is that turning screw MORE than 1/2 turn will take you OUT of proper range (20-70deg), whereas if the voltage method was used, meter would STILL show to be within proper (voltage) range....up to 3 full turns. Correct??
Also, on your LH2.2, is lean clockwise or counterclockwise??
vladimir