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Old 08-16-2005, 01:18 PM
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Moneypit SEL Moneypit SEL is offline
Now what?
Join Date: Jun 2005
Location: SE PA
Posts: 525
Originally Posted by stevenstevensteven
"NOx is produced when the combustion temperature is high. You might just pass if you short the aux fan switch for constant operation."

Moneypit SEL, are you suggesting that I short the aux fan so it is always on? I have noticed for some time that the engine operates at high temperatures. I believe I have a leak or something else that has caused a pressure loss in the cooling system and have not had time to diagnose it. Do you think this high temp operating condition could cause the higher NOx?
Yup. Heat causes NOx. Running the fan for the test may well allow you to pass. Shutting the engine off and allowing it to cool down may also work. There's nothing else in your test numbers to indicate any other type of problem.

What do you mean by 'engine operates at high temperatures'? Do you just think it too high, or did it used to run cooler? What temperature is it running at now? If it engine used to run cooler than it does now, fixing that will fix the NOx.
1989 300 SEL that mostly works, but needs TLC
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