I got a 89 accord fuel injection (everything stock). Just fail on the smog with high Nox . Check egr system, lifting the valve at idle then it dies. Also, it got 5 in vacuum at high speed. check timing ok. Temperter normal. Car runs normal. I put new spark plugs on it + new cat converter. It still fail with high nox 300 over the limit at both speed . hc+co Ok. Anyone got any idea how to fix it. Could valve ajustment help? Could it be the injectors? decarbonize, will it help, but how?

 

retard timing a few degrees
(i retarded mine to like 8)
and juss have the cat nie and hot when u go thru

that's what i did and it worked for me
(i was waaay over on nox too)

 

you need a new cat
I had the same problem,
tried everything, none of that crap works.
you cant retard the timing, the smog shop checks that and if its off you FAIL,

what I did was combine cx and dx exhaust piping/cats, to end up with 2 cats at once.

then i passed.

also make sure you heat the **** out of the cat before going to smog it,
drive really far, and really hard to the smog shop and do not turn off the car before smogging it.

all other stuff wont drop it 300.

OH,
that "guaranteed to pass" stuf might work,
didnt try it but heard good stuff.
it'll take a full tank of gas run thru tho

 

NOX = eccessive temps in the combustion chamber.

now whats the others ? post the stats on CO, and HC

 

hc 90ppm co .10% co2 15.1 % . I think it's running slightly lean. Is there any way i can rich it up a little bit?

 

don't richen it up any more... 15.1% co2 is great. richening it would just cause your co and hc to go up, and u dont' want that.

double check your ign timing, and try a decarbonizer. other things to check for... make sure your coolant temp really is ok, and that the coolant temp sensor isn't off. high engine operating temp would cause nox to go up. decarbonize the combustion chamber... carbon causes high compression... high compression= high pressure... high pressure= high temp... hi temp= high nox.

umm...

i know u said you checked your egr when you lifted the valve... is yours vacuum operated? if so... have u tried vacuum pumping the diaphragm? maybe there's a hold in the diaphragm. did u check for a good vacuum source? maybe try cleaning out the egr passages.

 

HC is sketchy... CO and CO2 are both ok...

Try retarding your timing a bit. NOx is nothing but high combustion temps, and timing does play a big part in that... Try checking your EGR system again, it may be "working" when you test it, but not when you are actually driving it.

I've seen plenty of Accords with clogged EGR passages...

 

The temperature is normal. The check egr is ok. When Lift up the egr valve, it will died at idle. hook up a T fitting with vaccum gauge to the egr vaccum line. It has a 5 " vaccum when driving. But the vaccum seem like on + off. So, i disconnect the vaccum line + pump the egr valve. It hold the vaccum good. Then , I try to open the emission vaccum box. I check the lines, no clog. I check the egr solenoid ground signal from the ecu. I put the car in 2nd gear + rev it up. The ground signal is on + off. Is this normal for old accord? I notice some newer model the vaccum provide when u just rev it up. What's a good way to decarbonize?