Mass air flow sensor

An acquaintance, backyard mechanic, messed with my air flow sensor setting screw. It ran okay for awhile, but now is running very rich as judged by mpg and the tailpipe black color. Mpg went from 34 mpg average to 29. He screwed it in alot beyond where the factory locked it in with some kind of RTV. He also adjusted the idle adjustment screw/locknut as the idle dropped way low. That was 4 months ago.

I looked at the manual. Says basically not to mess with it. Is there a ballpark region I can adjust the mass air flow sensor? The manual says 800 rpm for idle.

88 VW 1.8L Fox Dave
Reply to
Dave
Loading thread data ...

The adjustment is a little tricky. The engine needs to be at operating temperature before any tests and adjustments are made. The crankcase vent hose on the valve cover needs to be disconnected as well as the wire harnesses to the idle boost valve and DPR valve. With the engine idling, adjust your timing between 4 and 8 degrees before TDC. With your ammeter in-line with the DPR and it's harness you can adjust the CO screw by watching the current on your meter. Adjust to about 10mA. Only now can you adjust the idle screw. Set this to about 900 rpm. Hope this helps. Let me know if you need further assistance.

Reply to
Madesio

OK My question is WHY did that "mechanic" mess with the setting at all? I bet ya that the engine is running sluggish a little too! Might have clogged up the Oxygen Sensor too if the engine was running too rich.

Like Madesio said you can adjust the CO with a digital Volt Ohm Meter. A Bentley is always a nice manual to help you learn and do some repairs too.

Reply to
dave AKA vwdoc1

That's the manual I'm referring to, Bentley. As I stated, looked at it after the deed was done. Dave

Reply to
Dave

Thanks for some useful information instead of attacking me. I'll jump on it.

I think I backed off the mass air flow sensor a bit too much in an attempt to rectify. The idle adjustment screw has no effect. 1200 rpm idle. Idle adjustment screw backed off as far it it will go before hitting the manifold. Runs well otherwise. Mpg is up as well. Dave

Reply to
Dave

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.