Originally Posted by SilvrFyre
Anyone ever get their car smogged and had worse results while at idle than at 2500 rpm? I don't just mean worse either. It's waaay worse. Max Hydrocarbon emissions in CA on a 2.5gt is 100 ppm at idle and 130 at 2500 rpm. Average is 17 and 12. Mine tested at only 15 ppm at 2500 rpm, but at idle it was way up at 92! Is this indicative of something failing or about to fail in the engine or exhaust?
I also noticed that it was listed as a single exhaust system instead of a dual exhaust. Would him using only one wand in one of the tailpipes have helped me in this situation? Had he used two, would I have had double the HC emissions and failed to pass?
Run the usual stuff:
- Clean MAF
- Fresh spark plugs and clean ignition coils - slight misfires at idle can increase the HC.
- Fresh air filter
- Fresh oil/oil filter - old oil may leak more than fresh increasing the HC.
- PCV valve clean and working
- Leaks on the manifold
- Injector cleaner (run one tank with it before inspection.)
- Also check the intercooler if there's oil in it or the hoses leading to it.
- If you have had a TGV delete this can also contribute.
And right before inspection make sure that the engine has been up to working temperature. A cold engine/cat won't work as expected and cause more emissions. This is actually one of the reasons why cars fail over here sometimes - someone brings in a cold car to the inspection. (which also brings up the point - did they follow the correct procedure at the test station?)
If it still fails then you have more than the normal level of problems, and you shall start to look at:
- MAP sensor
- Compression test
- O2 sensors (one of them may be bad or off without being out of range completely)
- Injectors (A workshop clean and matching of them)
- CAT starts to go bad (But if you have this you shall also check all of the above since there's usually a cause for it to go bad)
Anyway - the high figures for HC and CO at idle aren't unusual and aside from a cold engine just tells you that it's time to do a more thorough service on the engine than what's stated in the service book.
And to understand how it all works - the combustion chamber on a turbocharged gasoline is a rather extreme environment seeing a pressure ranging all from 0.2 atmospheres to 2 atmospheres (peak values) in cold pressure that is then compressed to the compression ratio of the engine (8.5 to 10.5: 1) and it shall still be able to have a mixture possible to ignite through an electric spark.