Sounds like a lean misfire. Fuel injection cleaning using fuel additives will help but they won't work on one or two tank fulls. You have to use the product over a few months in order to is a difference.
You might consider a stronger fuel additive. Something that guarantees a passing smog test after one (max two) use. Certain engine problems cannot be masked by any guaranteed to pass smog check additive.
The right was to go about it is to do a compression test first. If you see high compression, an engine DeCarbonizing will clean out carbon and lower NO.
Clean out the injector by removing them and soaking them in injector cleaner solution over night. Smog stations actually have a injector cleaning machine which pulsates the injector manually while running a high pressure detergent through the injector. At home, we probably don't have this luxury.
posted by SmogTips Support
