[urq] Fuelsystem diagnostics part3

[j.koenig]

I can't remember whether your car is something unusual, but if it's the 'typical' U.S. 
spec, I think you also have to look at duty cycle, which is fixed by the control module 
under certain condition, and the idle and wide-open-throttle switches, which are inputs to 
those fixed values.  If you set things up without those switches and/or O2 sensor feedback 
loop working properly, I think you can get to a place where going to open-loop operation 
has the opposite of the desired effect on mixture.

I haven't thought much about this since working on my own car a while ago, so, my 
two-cents-worth only (experts please comment).
Good luck.
John

----- Original Message ----- 
From: "Patrick Carlier" <p.carlier at pandora.be>
To: <urq at audifans.com>
Sent: Friday, October 02, 2009 11:09 AM
Subject: [urq] Fuelsystem diagnostics part3


Today I took an intemediate step .
I should do the injector leak and yield tests .
But I decided to try and adjust the mixture strengtht first .


I don't have a four gas analyser , but I do have a wideband .
Innovate LM-1 , nice toy for a decent price .

So I started the engine , wich fired at the first crank :)
Allowed it to warm up and hooked up the wideband .

Idle mixture was waaaay to rich .
In fact it was so far off , it's a surprise the car would start .
Anyway , I adjusted to 14.60 , wich should be close to 1% CO at idle .
But then if I open the trottle just a bit an run the
engine at 3000RPM , AFR readings drop an remain steady
at 12.30 .  No that's pretty rich isn't it .

If started leaning the idle mixture to 16.50AFR .
Can't go higher cause idle becomes erratic .
Stilll , at  3000rpm I  get an AFR OF 12.85 .


Could it be that this rich condition is due to racing the engine with no load .
I can't take it on the road yet to do some real testing .
Does anyone know what AFR should be under normal driving conditions ?

Pat
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