Date: Sat, 11 Jan 1997 07:00:46 -0800 (PST)
Sender: Vanagon Mailing List <vanagon@vanagon.com>
From: Beth Young <young@sherlock.sims.berkeley.edu>
Subject: Re: fuel-injection runs really rich in my 81 2.0 vanagon
On Fri, 10 Jan 1997, dan perdue wrote:
> Will someone please help me. I am trying champion 302's (hotter plug) and
> it is o.k...
> Is there a way to adjust richness like cis-e injection in 80 Scirocco??
> I've fiddled with the screw near the air-box and noticed no real
> change...HELP
On modern cars the fuel injection is "set for life"; there's no idle or
idle mixture adjustment feature at all. The reason for this is that the
O2 sensor and ECU monitor the engine at all times, adjusting things
accordingly, so there's no reason to have these manual adjustment features.
Your '81 fuel injection is not that modern in that it allows you to
adjust the idle and idle mixture but, in theory, there's no reason to do
so since the O2 sensor and ECU are performing the same monitoring
function. So, before messing around with these things, check to see if
some element of the fuel injection has failed, causing the rich running.
A common failure is the #2 Temp sensor, located in the head above #3
cylinder. This can be easily checked with an ohm meter. Likewise the #1
Temp sensor can fail (not as common). It too can be checked with an ohm
meter.
What I'm saying is to check each element of the FI system out before
adjusting idle and idle mixture. If everyting checks out OK and it's
still running rich, and if adjusting the screw in the air flow meter
doesn't imporve things, then I'd suspect that the air flow meter itself
is causing the problem. There's a spring inside the air flow meter that
resists the opening of the air vane inside the meter. Over time this
spring seems to lose strength, giving less resistence to air flow, which
translates into the ECU setting a richer mixture than the engine really
needs.
Although all the books say that the air flow meter is not user
servicable, THEY LIE. You can adjust the spring inside, fixing this
problem. The Vanagon archieves detail the adjustment; if you can't find
it ask me and I'll tell you how.
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Tom Young young@sherlock.SIMS.Berkeley.EDU
Lafayette, CA 94549 '81 Vanagon
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