gunmetalrps

I had to get my car smogged today, and as I feared, it failed. here are the results:

1990 KA24E, 87 octane, rear tires inflated to 32 psi (205/65)

Timing at 14 BTDC
15 mph test @ 1722 rpm:

%CO: 13.4 %O2: 0.7 HC: 124 (Max is 121) CO: 0.85 (Max is 0.76) NOx: 2552(Max is 807)

25 mph test @ 2830 rpm:

%CO: 14.3 %O2: 0.1 HC: 31 (Max is 96) CO: 0.64 (Max is 0.65) NOx: 1817(Max is 746)

By what i understand from these results is that the engine is running very lean. Whats weird is that at higher RPMs it seems to be burning the gas efficiently but at standstill, if i rev it to about 4k rpm, i can see a tint of black smoke from the rear which would signify that its running rich, plus i smell it.

so i went home and read the codes for the ecu, and as it usually shows, the culprit was EGR, and also code 45 which is injector leak. could this be the reason why it could be running rich at high RPMs?

i dont have a pressure pump but what i did do was follow the FSM regarding testing the EGR, i pushed the valve up and the car started stuttering, BUT it didnt stall. by FSM standards, this would mean that the EGR is fine.

so im at a loss of thoughts now, idk what to do. if i replace the plugs/cap/rotor/wires i know it'll burn the gas MORE which means higher NOx. could i bypass the BPT valve and just route it straight to the EGR. will this open the EGR and be effective with the car running at 1722-2830 RPMs

One last thing, regarding the injector leak, exactly what does that mean? is it spraying more that it should, but not too much to make my CO off the roof, yet enough to fail it? how would i go about testing this?

any help or suggestion will be greatly appreciate and thanks in advance. sigh

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cc4usmc

bored smog tech here

I didn't post that so you could post there. I posted so you could read...not that that's the only smog thread..

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lost240soul

if your hc readings are right it shows that u did fail for hc on your 15mph test.. this could be caused my leaky injector.. also by anychance how long did u drive the car before u took it to get the test done..usually takes about a little while for the cat to light off

gunmetalrps

i think that was one of the biggest mistakes i made. i was in rush cuz of so much going on today that i really didnt drive it around much at all. also for the HC, on my previous smog test it was 43, what would cause this big of a jump, yet not on the 25mph test. the 25mph test actually even had a lower result than the last smog test. 31 vs. 33. ive been reading ALL the previous smog post just as cc4usmc recommended but im just baffled at all the inconsistencies.

also i got restless so i went out to recheck the EGR, the valve works but when when i rev the engine i dont feel it moving. could this be from the solenoid. i checked for vacuum leak and didnt find any.

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mxexux

A leaky injector would help with the NOx levels but hurt you with the HCs. Leaky injector is a possibility in your case but the NOx problem is going to be something else most likely the EGR. NOx occurs with high combustion temps, but a rich condition only cools the combustion chamber. I hope this helps you narrow it down.

mxexux

Oh yeah as you might already have found out by trying it, dont bypass your BPT solenoid because it would open the EGR all the time and make your car run like shit and stall on idle. EGR is only supposed to open at part throttle light load.

lost240soul

yea it could possible be that the cat was not yet at opertaion temp..also the reason your hc's are lower in the 25mph test is because more air is leaning out the a/f ratio..also for the egr,check vaccum on that one hose i think its on the solenoid..

CrimsonRockett

My car failed smog not too long ago due to high NOx.

I had an old cat(aftermarket replacement that sucked) and a stock exhaust missing the mid section muffler/resonator(rusted out, previous owner had it chopped off and replaced the section with a straight pipe).

Swapped the cat out with the original one my car came with(OEM cat), re-installed my original stock exhaust(with both mufflers/resonators).

Passed super easy.

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Folken

I had the same issue and it ended up being my cat, could not hurt to get a new one, pay the extra money for the direct bolt on one too, unless your going to pay someone to swap it for you

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gunmetalrps

i have no problem with replacing with the cat, the only problem is that the old owner instead of using the flanges on the cat to connect to the rest of the exhaust, its welded to the whole cat-back system. so to replace the cat means replacing the whole catback system. ughhh. why can't people do things right. so im trying to rule out the cat as much as possible, but its looking like its the cat thats causing the problem.

any other ideas, anyone?

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Monooxide

Also, lower timing will give you LOWER NOx and RISE with too much timing. Adjust your base timing down.

Also really lean mixtures will cause the NOx to go up but HC and CO will fall. So you'll want a balance of "too rich". Possibly walk your base fuel pressure up if you can.

Just some advice.

CrimsonRockett

You know, exhaust shops *can* cut the exhaust near where the flange used to sit and and weld a new flange back on.

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Fixing iDesigns shitty work since 2008.
CrimsonRockett@blogspot

blackrms13

if u still have a leak somewhere in the EGR system, then the valve will still not open, which in turns increases the NOx level

i had similar problem
my egr was clogged, manually pushing up that valve did not help at all
i had to clean the whole intake manifold...
after that, nox level was still high, but if i used a hand vacuum pump to partially open the egr, that lowered the nox level significantly

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91' 240sx Fastback

Monooxide

The EGR Valve vacuum hoses back there as well as the swirl butterfly valves on the solenoids are VERY prone to cracking and having huge holes.

Also, if you have no means of richening up the mixture like mentioned, some small holes in vacuum hoses or loose hoses should richen things up a bit.

ZX88

my stock auto ka never passed smog. i bet my sr runs cleaner than that engine ever did.lol

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CHROME EMOs

miklos

I went to Test Only and all Visual passed but my NO at 15mph was 3652 and at 25mph it was 3045. This was tested in California. My cat is 2 years old.

The odd thing is if I join the 2 vacuum lines going to the AIV--the car idles 100rpm higher and much smoother.

xplicit240

man i really feel bad for you west coasters for that whole smog deal over there.

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miklos

Smog test update:

I just failed for the 3rd time.
After the 2nd time:
I replaced the spark plugs and plug wires, O2, EGR solenoid, cleaned out the EGR ports, 2 new fuel injectors, new vacuum hoses, and the MAF.

15mph NOX 2803
25mph NOX 1276
15mph CO .87

Do you think a new cat would fix all of this?