Hi all,
I just completed an installation of a voltmeter, oil pressure, oil temperature and a vacuum gauge in my stock, 1990, 2.1 WBX with 105,000 miles. No leaks, no smoke. Everything nice and as it should be - except for the vacuum gauge. At idle, instead of reading the expected 20 In. Hg, it reads about 13. When I rev it up and then let go of the throttle, the needle will get to 20, but then go down into the 13-15 In. Hg. range.  I've got the 1/8" vacuum tube Teed into the hose between the Air Plenum and the Fuel Pressure Regulator. I've tried two different vacuum gauges to verify that the dashboard gauge is reading properly.
I've verified the ignition timing at 35 degrees BTDC @ 3000 RPM with the temp sensors connected. The engine runs perfectly and makes as much power as it ever did. I'm confused. Can anyone offer any help?
Thanks,
Mike M

Sent from my iPad