Emissions!!

[larrymoencurly]

You may want to ask the state emissions lab because they have some real wizards.

High HC and low CO means bad ignition or too lean a mixture to allow for ignition, but because the CO is extremely high CO under load, I think your HC problem will disappear if you fix the CO problem. 5.29% CO is about what an early 1970s car would put out.

Auto parts stores generally can't read out the computers of pre-1996 model year cars because the computers weren't standardized back then, but those Nissans had a way to read out several diagnostic codes by looking at blinking lights on the engine computer. On my Nissan the computer is under one of the seats, and to enable diagnostic mode you have to rotate an adjustment all the way clockwise or counterclockwise with a screwdriver.

NICOclub.com (NICO = Nissan-Infinity Car Owners) has great forums and also factory service manuals.

[Dangerous Dave]

Originally Posted by vmsbmvp

I have a 1993 Nissan Sentra that didn't pass emissions. Idle passed with 202 HC an CO of .03%. Failed loaded reading with 288 HC and 5.29% CO. Standard being 220 HC and 1.2% CO. There is no check engine light on! Is there way to pass without spending a lot of money. Can I take to auto parts store to have tested? Does anyone know good emissions mechanic?

There's still a '93 Sentra on the road? 1993 was before decent diagnostics on cars. The only reason your check engine light would come on in that car is because the temp is too high or the oil pressure too low. It doesn't monitor any of the emissions related parts.


If the spark plugs haven't been changed or looked at, that is where I would start. Also, if it has a ton of miles and the O2 sensor hasn't been changed, that could also be a culprit. It can make the fuel injection run rich.