1990 Acura Integra Failed for High NO

Hi, My car, a 1990 Acura Integra recently failed a mandatory smog check at a star facility after readjusting the timing back to TDC (16°+/-2). Initially, the emissions portion passed with the timing advanced to 19°,the NO (PPM) was measured at 763, max was 807 and avg. was 420. But due to the advance timing the overall test failed

I went home, then the next few days I consider my options and returned to the same shop and asked them for a retest after they adjust the timing and wouldn't you know it, it failed this time at TDC (17°) the NO measured 831 and max and avgerage stayed the same.

The smog technician at the shop told me maybe if I drove it around a bit, it would help. Taking his advice and troubleshooting what else could be the problem, I realized it, the gas! It's old and cheap because I rarely drive this car my question is: Since it just barely failed what if I used some fuel additive to flush out the old stale gas and use Chevron super with techron and have the shop advance my timing to 18°(still within the factory spec of 16°+/-2...do you think it may pass the smog check?

Answer:

Fresh fuel with Techron will definitely help your Acura Integra pass the smog check especially considering the fuel you've been using is old and will not burn as efficiently as fresh fuel. The timing question is a little tricky however. Typically it's retarded timing which lowers NO emissions, and not the other way around. With advance timing you get a more thorough burn but higher NO emissions as well; so you'll see lower HC and CO but higher NOx.

Our recommendation would be get the smog check with fresh fuel and timing set to as low as possible without going over the engine (and smog check) requirements. If your Acura still fails the smog check have the high NO problem diagnosed. Either your Acura Integra is running too lean (due to a variety of possibilities including vacuum leaks, dirty injectors, defective oxygen sensor) or engine compression (internal engine temperatures) is too high. NO is created when combustion temperatures rise over 2500f. Keeping the engine running cool helps lower NO. Things like high octane gas (though we recommend only using the manufacture required Octane), fuel additives will keep NO as low as possible; however with an engine that has a serious defective which is causing high NO these remedies will not work.

posted by SmogTips Support