ok, here's the deal. i have a 92 civic cx hatch and it keeps failing smog. the CO, HC, n all that stuff is fine, it runs like perfectly, except for the dam NOx. One problem is the gearing, it's too low to run the 15mph test in 2nd gear, so the tech runs it in 1st gear, n it revs too high, about 2400rpm. He said the NOx level is fine until about 2200rpm, but as soon as it hits bout 2300-2400, shoots up over the limit. The 25mph test is great, well within spec and it's revving at about 2200 in 2nd gear. One option i thought of was try an EX/Si tranny because that way it could be in 2nd gear for the 15mph test and it would pass fine, but then i worry the 25mph test might rev too high in 2nd gear. Anyways, I am currently running 91 octane and i'm thinking it might be the cause? Anyone think for my bone stock b15 that 87 octane may actually help it pass smog? Please help!

 

d15 you mean? maybe help slightly, since you don't even need to use 91 octane. good luck.

 

I had the same problem, but with a dohc. I changed my Cat and that seemed to fix the nox problem. Passed!

 

u mite trying changing ur cat..but i heard if u get racing fuel it burns really clean...but that only if u have a place that has racing feul

 

For higher performance engines, but for d series, especially non vtec, I don't think it makes much of a difference. It's probably just a hollow cat...

 

Using 91 octane is retarded, you don't have the compression ratio to justify that.

What's your timing set at? Retard it a couple of degree's from where it's supposed to be.

And do NOT use racing fuel.

 

My old roomate had the same prob. He unplugged injector #3 and passed. Can will run shitty, but it'll run. Might want to give it a try.