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Your car is running lean.
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Posted by Bill S. [Email] (more from Bill S.) on Sun, 16 Oct 2005 14:56:17 Share Post by Email
In Reply to: Never mind. I've figured this out, its not vacuum, John Roberts, Sun, 16 Oct 2005 10:02:24
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I went back and looked at the numbers you posted earlier (HC, CO, NOx), and your car is running lean. Check out the curves in the attached link. The high NOx is because your cylinder temps are high, because of the lean condition, in that order.

You are absolutely right about the O2 sensor not working until it comes up to temp. It doesn't start generating a signal until it's hot. For this reason cold starting problems are never O2 sensor problems.

Until the O2 sensor starts generating a signal the ECU runs in 'open loop mode', doing its best to meter the fuel with no feedback. The extra air (or lack of fuel) is fouling this up. I believe that the reason our cars run poorly when cold and lean is that the ECU is using an uncoordinated combination of fuel and AIC fluctuations to try to keep the car running, and can't. Once the O2 sensor kicks in the ECU can use the feedback to keep the car running, but probably spends more time on the lean side of .5V.

posted by 67.183.219...

Emissions analysis

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