KA24DE S13 vert won't pass emissions in Atlanta- high NOx

[ftl900]

I just bought the car, so I know little (or less) about it. 180k with a 5 speed conversion.

Georgia emissions has a double test, 25/25 and then a 50/15. The car was very well warmed up after a 40 mile freeway drive.

After passing the 25/25 for HC, 136 HC (ppm) is allowed on the second test and I ran 184, so that failed.

The NOx was really out of range, with 945 allowed and I ran 2895ppm on the 25/25 test, and then 1045 allowed while I ran 3528ppm on the 50/15 test.

I don't have a million dollars to dump into the 'diagnose by replacement' method of fixing it. I read a bunch of posts, and suspect that cleaning the MAF and EGR would help... if I knew where they were or what they look like. Maybe a new cat... I called a local shop and they wanted $85 just to diagnose what it needs, and I'm a little leery of their diagnosis when they're drooling over the estimate.

So my CO is a little high, and the NOx is way high. Any suggestions on where to start? I'm hoping for some cause & effect here, so can logically clean & replace what is needed without randomly tearing into things.

Thanks a bunch. You guys are the bomb!

[12Ounce]

Have you pulled the codes? (I think that's a proper question concerning a '93 ...???)

Sounds like you are not getting enough EGR feed into the inlet air stream. Check the vacuum hose that opens the EGR valve. On the KA24E engine I'm currently rebuilding, that particular hose was in shreds.

[3Q Jay]

EGR quenches NOx. make sure you have vacuum at part throttle to the valve (will/should be zero vac at idle). then once that's remedied, you're in for some serious EGR crud cleaning.

[ftl900]

Okay. I don't think it has codes, but I will learn about it... time for a shop manual tomorrow, so I can find some of these things.

Thanks!!

[dkdeleon68]

check you O2 sensor also.

[Q45tech]

99.99999% of the time high Nox is EGR related assumming the base ignition timing is correct.

O2 always need replacing frequently to optimize HC and MPG at cruise.

Buying a used car always means you buy someone elses problems.

Doesn't the seller have to provide you with a passing emission certificate to prevent emission fraud?

"I just bought the car, so I know little (or less) about it. 180k"

[ftl900]

Yeah, it's supposed to work like that, but the kid I bought it from got taken to the cleaners when he bought the car only 2 months ago.

I got an okay deal on it, and wasn't going to push it any more by tossing it back in his lap. He bought it this way, and pretty much let it sit for 2 months while losing a bunch of money in the process.