Failed smog Pretest.

[Rotary#10]

Hey folks I have a bit of a problem now. I failed a smog pre-test On my 90 gtus n/a/ Everything else is fine but my NOx it thru the roof. Either I have alot of carbon build up or my engine is on its way out. Im thinking its the carbon build up. Whats recommended to clean it? Steam cleaning? Seafoam? The stuff Mazda sells for 50 bucks a bottle to clean the engine? Also the tech said my engine is ping-ing. Sigh*

[NoDOHC]

NOx indicates high combustion temperatures and excess oxygen. It basically means that your engine is running lean or hot or both. Advancing the timing is the fastest and easiest way to make NOx. Running ethanol-rich fuel is a good way to run lean (although you shouldn't with a functioning O2 sensor).

Carbon buildup may be the reason for the pinging, but I doubt that it is causing your NOx emissions. It is possible, but not likely.

Possible causes:
EGR not functional - (not an issue, s5s had no EGR)
Ignition timing too far advanced - (likely, especially considering the pinging)
Cooling-related problem (possibly running very hot combustion because the coolant flow is inadequate near the combustion region)
Carbon buildup (a stretch, but could be insulating the rotor from cooling the charge and storing combustion heat over time)

To fix the carbon buildup, I usually beat the car really hard for a while and then while it is still hot and idling, take of a vacuum line and stick it in a 1 liter bottle of water. You will see a cloud of white smoke and it should largely clean your chambers.

You can try the other stuff, but most of it works on the same principle as the water, flash cooling of the carbon makes it fragment and go out the exhaust in little flakes

[Rotary#10]

Originally Posted by NoDOHC

NOx indicates high combustion temperatures and excess oxygen. It basically means that your engine is running lean or hot or both. Advancing the timing is the fastest and easiest way to make NOx. Running ethanol-rich fuel is a good way to run lean (although you shouldn't with a functioning O2 sensor).

Carbon buildup may be the reason for the pinging, but I doubt that it is causing your NOx emissions. It is possible, but not likely.

Possible causes:
EGR not functional - (not an issue, s5s had no EGR)
Ignition timing too far advanced - (likely, especially considering the pinging)
Cooling-related problem (possibly running very hot combustion because the coolant flow is inadequate near the combustion region)
Carbon buildup (a stretch, but could be insulating the rotor from cooling the charge and storing combustion heat over time)

To fix the carbon buildup, I usually beat the car really hard for a while and then while it is still hot and idling, take of a vacuum line and stick it in a 1 liter bottle of water. You will see a cloud of white smoke and it should largely clean your chambers.

You can try the other stuff, but most of it works on the same principle as the water, flash cooling of the carbon makes it fragment and go out the exhaust in little flakes

I will try the water method as you suggested. Timing its on factory specs. well looks like i have to buy some quality gas now. Thanks for the insight. Ill post back about the outcome of the water method.

[NYsNumba1Man]

as stated on the 7club



set the car a bit richer and/or put better gas in

[Rotary#10]

Okie the tech said i have load issues in 2nd gear. mmm Im think im CAS may not be stabbed in correctly.

[Tanj!]

Originally Posted by NYsNumba1Man

as stated on the 7club



set the car a bit richer and/or put better gas in

What is the run-in converter?