Re: Fuel Mixture Question - CIS FI

[Alan Stamper <stamper@iwaynet.net>]

At 01:10 PM 5/5/97 -0500, you wrote:
>At 12:48 PM 5/5/97 -0500, you wrote:
>>
>>I have a K&N Fuel/Air monitor on my 81 Scirocco and I am noticing a VERY
>>DISTURBING TREND!
>>
>>The mixture REALLY LEANS out after the engine has been running for 20 - 30
>>minutes!
>>
>>At start-up mixture is great, drive around town for 20 minutes (no
>>hot-rodding) mixture is still great. Run the hell out of the Rocco (6 ax
>>runs and 70mph for 30 miles home) and the mixture REALLY leaned out (OFF
>>THE GUAGE). Engine runs fine and temps were not too unusual, just don't
>>need a burnt valve!
>>
>>Any hints?
>>Harry
>
>
>Bad or failing ox sensor. (id suspect this the most)
>maybe (doubtfull) the plate in the airbox isnt alligned properly. 
>
>The ox sensor is solely responsible for setting the fuel mixture. When the 
>car is cold, you have got the 5th injector helping with the fuel. (Rich) 
>After the car is warmed, its down to 4 injectors but the ox sensor is 
>thinking its running right and it leans out the mix. (good theory, no?) 

Shawn, I agree with your idae of the O2 sensor possiby being bad.  The
fifth injector only operates for a few seconds at start up.  It could not
be the reason for such a drastic mixture change unless it were operating
incorrectly.  Whatever the case it would seem the problems start after the
thermotime swith has tripped.  I'd also check for a faulty warm up fuel
pressure regulator on the block.  It might also be possible that the base
fuel mixture setting on the distributor is so far out of whack that O2
system can't compensate for it.  This would cause the idle speed will cycle
up & down as the O2 system trys constantly to make the correct air/fuel
mixture (at least this is what it did on mine)

Alan

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