Date: Thu, 4 Feb 1999 15:42:38 -0800
Reply-To: Tom Young <young@SHERLOCK.SIMS.BERKELEY.EDU>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Tom Young <young@SHERLOCK.SIMS.BERKELEY.EDU>
Subject: Re: FI mixture adjust?
In-Reply-To: <19990204220253.25887.rocketmail@send104.yahoomail.com>
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Mac:
Yes, you can have a too-rich situation with a FI vehicle, particularly
with an older car.
If you have a Vanagon with an O2 sensor, you can determine if the mixture
is too rich by monitoring the output of the sensor with a digital
voltmeter. With the car completely warmed up, stop the engine,
disconnect the O2 sensor and attach the voltmeter to it. Start up the
engine again and see what voltage the sensor is putting out. If you see
something on the order of .5 volts (what you typically see is a rapid
fluctuation above and below this figure) then the mixture is probably
OK. If the sensor is putting out way more than .5 volts (.9, 1 volt)
then the engine is too rich. (This is assuming that the ignition system
and mechanicals of the engine are OK. If they're not, then you put these
things right before messing with the FI.)
If you find that the engine's too rich, then you really should do a
step-by-step diagnosis to determine what's wrong (check temperature
sensors, check fuel pressure, etc.) but a very common problem with these
older cars is that the spring in the AFM that resists the movemement of
the air vane gets weak over time, enriching the mixture at all levels.
Sometimes this weakened spring condition is so bad that you can't adjust
the mixture back to the right level using the mixture adjustment screw,
even it you turn it all the way out.
You can tighten up this spring by removing the platic cover on the AFM
and winding the toothed "wheel" under the spring clockwise, monitoring
what's happening with the mixture by watching your voltmeter.
If you don't have an O2 sensor on the car, then I guess there are some
"seat of the pants" ways of adjusting the mixture and getting it more or
less correct, but I'm not familiar with these methods. Maybe the best
thing to to in this case is to take it to a shop with a CO tester and
have them set the mixture properly.
On Thu, 4 Feb 1999, mac stricklen wrote:
> A friend with a little more mechanical experience than me was helping
> me fool around with the engine on my 1980 Westy this afternoon and he
> took a whiff of the air around the running engine and told me he
> thought my mixture was too rich. Could this be so on a Fuel Injected
> engine? If so what sort of symptoms would it be producing and what
> can I do about it?
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Tom Young young@sherlock.SIMS.Berkeley.EDU
Lafayette, CA 94549 '81 Vanagon
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