What makes NOx

[2speed]

Not exactly specifically Ford related, but I have a car that is having trouble passing emissions because of high NOx. It has low HC's which I guess NOx is caused by a lean burn condition? What can I do to help this?

 

[BIGREDRASA]

High combustion temps produce NOX. One function of EGR (Exhaust Gas Recirculation) is to lower those temps. You might try richening the mixture a tad, or cleaning out the combustion chamber carbon to lower compression. See: http://fordsix.com/forum/viewtopic.php? ... ight=water

 

[FloridaRustang]

Water or alcohol injection should work, too.

 

[2speed]

This is in an old H*nda. The timing wasn't at spec, I put it back to spec and it got worse. The EGR seems to working, I can suck on it and get it to move, and the line to it is pulling a vacuum. Should I do the old water spray at high idle to clean it up a bit? Retard the timing some?

 

[Lazy JW]

That wouldn't hurt to try the water spray trick to help clean things up. as was mentioned above, high temperatures cause oxides of nitrogen to form. When auto emissions were first being addressed, the older engines put out a lot of unburned hydrocarbons. The easiest way to correct that is to lean out the mixture and raise combustion temperatures. Voila! Lower HC emissions. OOPS! The temperatures were now high enough to cause the nitrogen in the air (air is mostly nitrogen) to begin oxidizing. It was found that one easy way to lower the burn temperature was to inject a small amount of an inert gas into the combustion chamber. But where to find an inexpensive source of inert gas? Enter the infamous EGR (Exhaust Gas Recirculation). Exhaust is pretty much an inert gas, since it has already been burned. Now inject some exhaust gas into the intake during times when high combustion temperatures are likely, and turn it off when temps will be lower. Another problem with lean burning is poor idle characteristics, stumbling, eratic, etc. So we opened the throttle a bit more to allow more air flow(or increased the air bypass, whatever) but now the idle is too high. One way to slow the idle speed down is to retard the ignition timing, so that's what many car makers did. That's where the various forms of dual vacuum advance/retard distributors came from. Are you confused enough now? I know I am
Joe

 

[SuperMag]

After enriching the mixture some, you may try adding 1 gallon of alcohol to about 8 gallons of gas. That might work; I used that trick to get an old Subaru through Ohio's e-check one more time.

 

[FastRonald]

8) Okay...here's a trick that has been effective up here in the Chicago area..add two bottles of HEET to your gas tank and then test it. Most people I know who have done this....have passed. Okay, so it's not the best, but will give you time to sort out the real problem.