I would like to find out what would cause the hydrocarbon readout from an emmission test to almost double in two years. The maximum allowable is 49 ppm.

I went from 27 to 48 in two years. Any ideas?


Unburned hydrocarbons will cause a high hydrocarbon reading. How long has it been since you changed your plugs, air filter, O2 sensor, or ran some injector cleaner (if so equipped) thru it?


Thanks for your suggestions. I will investigate the past services done on this vehicle. Luckily, I have all the service records.