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Old 08-26-2010, 04:01 AM   #23
quantumech
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Join Date: May 2009
Location: Seattle, WA
Posts: 750

2000 SL1
Default Re: Jerky Saturn problem narrowed down to EGR valve. What next?

BennySL2: Sorry, I went out for a backpacking trip to blow off some irritation and steam before the job hunt begins (again...sigh), didn't see your message, but glad that it looks like you figured out your problem.

1996SL11.9L and fdryer: perhaps we can take a quick look at the chemistry involved. The main point of EGR is to reduce NOx emissions, which are very environmentally unfriendly (contribution to greenhouse gas, acid rain, etc). What happens when it's recombusted is the N and O's dissociate from each other, forming elemental nitrogen and oxygen, which then can go off and react with hydrocarbons that are present. Or the monotomic oxygen reacts with the nearest hydrocarbon, it would really depend on what it runs into first. The formation of N2 is a very energetic and exothermic process (why compounds containing nitrogen tends to be used in explosives), which can drive the oxygen and hydrocarbon reaction for that split second after the spark.

In the end, there is probably a small effect on lean/rich, but if the system is working correctly (notice the "if"), it shouldn't have a dramatic effect in either direction. I would imagine that during one cycle it could be lean, the next rich with the EGR in operation, depending on what the oxygen sensor is reading.

But that's just a guess (what the car is thinking, that is), I'm just a chemist, not a mechanic afterall. I'm just thinking about the chemistry of the situation to try and help you guys out.
...
Sasha: 2000 SL1, Manual, cracked head Sept. 2014. Donated Dec. 2014

I learn from my experiences. If I screw up, I'm sorry.
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