Help me understand my EGR/Emissions issues. (1 Viewer)

[DancesWithMutts]

I Failed a CO emissions test last week with high Nox. Today I put 50 psi in my tires, a bottle of heet in the gas tank and I lowered it a good bit but still failed. The first test I was 4.5 with the max being 4.0. The second test I hit 4.1.

I have read that EGR problems can cause high Nox so I cracked my FSM and tested some things, I was hoping you guys could help me make sense of the results.


During the test with the "T" connector between the modulator and the EGR, I read high vacuum at 2500 rpm. from what I understand, this is wrong.

I tested the vacuum modulator and was barely able to get any air through port Q (while blocking off the other two ports) regardless of engine RPM. I also tried putting a vacuum pump on the bottom port and was still unable to get any air through port Q with or without vacuum applied.

I applied a vacuum to the EGR itself with the engine idling and it immediately died. Which from what I understand means the EGR itself is working.

So here is my understanding of the situation, The Modulator has failed, which is allowing the EGR to operate more often than it should. Shouldn't that lower my Nox if anything? I understand that more EGR means my engine is running less efficiently than it could, so I will replace it either way, but this probably isn't going to help my emissions issue, right?

I also found that my intake tube is cracking, and was already repaired by the previous owner, so I ordered a replacement. Should I test my O2 sensors next?

 

[Corbet]

If I lived on the front range I'd buy a timeshare somewhere in the high country, then register my junk there, making sure it came due the same week of the winter I spent skiing in said time share.

Other than that I can offer no words of actual wisdom.

 

[beachboyy]

I can't speak for smog since we don't have it. But I dealt with a cel for a long time that had to do with the emissions system. I found the same thing when I tested the egr vacuum modulator. Replaced it with a new one and never got another cel light. Not saying that's it but if you can't get air through port Q while blocking the others then it's time for a new one regardless.

 

[Pin_Head]

If the modulator fails the FSM test, get a new one. They are cheap. High NOx means not enough EGR, high combustion temp or bad 3 way catalyst. The EGR is more likely.

 

[landtoy80]

Get new EGR modulator.

You can remove and clean the cats and O2's citric acid oxalic acid with . Helped with my Colorado test. Passed with very old O2's and original cats.

I also changed my oil to G-oil. All I could find was the small engine version. You can get G-oil online. Its veggie oil so has less emissions.

Look in the O2 electrical plugs for corrosion.

Fill up with Shell gas and take a long ride for a tank or more. Make sure its all hwy miles.

Do a good tune up, new plugs wires air filter etc.

Dont go to the same testing place. If you do go to the same place, try and get a different operator to do the test. The test results can change from: time of day, weather conditions and even from tester to tester. A tester with bad timing will mess up the test.

 

[Reelitchy]

Was wondering what year cruiser you have?
You didn't mention that you are getting a CEL light so I am guessing your not. That would tell me that your egr system is probably working properly. When they tested your vehicle did they put it on the rack and take it up to speed (if it's obd ). Was wondering because the egr is not used when the vehicle is stationary. NoX can also be a symptom of a poorly working cooling system.

 

[DancesWithMutts]

Was wondering what year cruiser you have?
You didn't mention that you are getting a CEL light so I am guessing your not. That would tell me that your egr system is probably working properly. When they tested your vehicle did they put it on the rack and take it up to speed (if it's obd ). Was wondering because the egr is not used when the vehicle is stationary. NoX can also be a symptom of a poorly working cooling system.

It's a '94. The cooling system has always worked flawlessly, the needle has never been above the halfway point on the gauge and the coolant and oil look great. I have no CEL, and yes they do put it on the rack and run it at speed.

 

[Reelitchy]

You probably do have a egr fault. Paperclip should help you see if it has one. Mine had an egr code 71 for the longest time without the cel. I reset it an now I have the light, so now I have to get in there and fix it.

 

[inkpot]

If one bottle of heet got you that close, I would think 2 or 3 bottles would do the job. Lots of folks have been known to run a at of alcohol in a quarter tank of fuel to pass.

 

[Reelitchy]

Yes, possibly run premium gas too, don't erase the code if you have one with no cel, then you'll have to fix it for sure if the light comes on.

 

[DancesWithMutts]

I took my EGR off today and it wasn't clogged up, and the diaphragm moved properly with vacuum applied. Yesterday's test showed me that the EGR is opening earlier than it should, so I am still thinking that I am getting too much EGR. I already ordered the Modulator, which should fix the issue of it opening the EGR valve at inappropriate times, but I still don't think that's going to help my emissions. I'll try a second bottle of heet next time around and hope for the best.

 

[landtoy80]

From reading many posts and talking to people that live in front range Colorado, the consensus is that you need new cats to meet the lower standards that Air Care Colorado has implemented. Had the old limits still been affect, you would of passed with your numbers. Everything needs to be working at its best to pass. Clean motor oil, working EGR and O2, new or cleaned cats. Carbon buildup on the pistons will raise emissions levels too.