of grey smoke? My 88 Maxima was deemed untestable by the local emission site because it was smoking too badly. It runs fine, starts fine, and accelerates fine. Any ideas ...?

Thanks!

 

I had a problem with my car and the white-grayish smoke but mine was also running weird. I replaced the fuel presure regulator and the problem seems to have disapeared a long with a lot of my other problems which included idling and running crappy. Bad millage. And caused the fuel pump to squeeeeeeel like a piggy. Although this may not be your problem it may be worth looking into. Also I recomend speedy car parts to get one from if you need one.

www.speedycarparts.com

 

Not sure what you mean by grey smoke. If it's dark grey, it probably means that the engine is running rich, so it could be something relating to the injectors or possibly even the timing. If it's whitish grey, then your head gasket or some other connection might be leaking coolant into the combustion chambers.

 

I took the car back to the testing station, got it tested, and it failed. It reads high on both HC and CO. I found a list of possible causes:

Normal levels of carbon monoxide (CO) and hydrocarbon (HC) indicate that your vehicle is fuel-efficient. On the other hand, high levels of either CO or HC or both, reveal an inefficiency problem. The probable causes of high carbon monoxide (CO) in your vehicle are listed as follows for you to further discuss with your mechanic:

1. Rich Fuel Mixture
2. Plugged PCV Valve or fuel in the crankcase ventilation system
3. Dirty Air Filter
4. Malfunctioning closed-loop fuel metering system
5. Saturated fuel evaporation canister or malfunctioning vapor purge system


The probable causes of high hydrocarbon (HC) in your vehicle are listed as follows for you to further discuss with your mechanic:

1. Electrical Misfire
2. Too Much spark advance (or initial timing)
3. Air-fuel mixture too lean
4. Vacuum leak
5. Leaking exhaust gas recirculation (EGR) valve
6. Malfunctioning closed-loop fuel metering system
7. Engine wear


I also read that a faulty oxygen sensor could be a cause for high readings.

Could a dirty air filter cause the air/fuel mixture to be too rich or too lean?

 

if the air filter is dirty, less air is able to get into the combustion chambers, so you get a rich air/fuel mixture

 

The discrepancy between high CO and high HC -- rich mixture/lean mixture -- appears to establish that high HC isn't your problem. What you've described sounds like a rich fuel mixture, as I initially surmised. As kiwikev notes, a dirty air filter could be contributing factor to a rich mixture. I'd be inclined to change the filter and follow through with the O2 sensor. Do you know when it was last replaced? I had one installed about 20 mo. ago, and the fuel efficiency 'experts' said that it needed replacement again about 8 mo. ago! The sensor is pretty easy to get at -- right at the front of the engine in the exhaust manifold, angled slightly to the right if you're facing the engine. It shouldn't be difficult to do yourself if you've got the tools -- especially a crow's foot O2 sensor wrench. They're very like spark plugs, with a compressible gasket. I don't know offhand what they're torqued to -- presumably someone has logged this info elsewhere on this site -- but in my experience they typically give a fair amount of resistance before loosening, but then screw out easily. The electrical connector is fairly short and it is fixed in a bracket, just a few inches to the north of the sensor. You haven't mentioned plugs. When was the last time these were changed? And what kind are you using? If, by any chance, you have platinums, I'd suggest going back to regulars. Good luck.

 

try turning your timing down

 

I had a issue with my 87 flooding its self out, when I took it in to the dealer I found out there was a recall on injectors and wiring harness. You might want to check into that

 

How is your catalytic converter? Those are essential to passing emissions test's.... (although i dont have one... cause there are no emissions testing where I live)

They help alot at burning up that unburned stuff.

A bad MAF or 02 sensor could mess up your AFR, thus causing your car to pump out high level emissions, as well as a FPR, or vaccuum leaks.

Some times you can mess with your timing to effect your emissions... there are also some fuel additives that are supposed to make your car pass emissions. (not sure if these work or not)