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I have a 1993 Honda prelude vtec and I am not sure why my car is failing smog so badly. Basically everything is too high. Some of the levels are just a little over, but some like the NoX is way way too high. The guy said I was running really rich and had unburned fuel passing through and I am running too hot. NoX was supposed to be around 705 and I registered around 3k. I don’t have the exact numbers as I left it with a tech at work and will post numbers once I get the sheet back.
My question is, what would i need to look at to get the car to run leaner and cooler to get some of those emissions down? I know its a bit harder without specific numbers, I just wanted to see if anyone could suggest something that may be wrong.
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Could be a number of things. see if this helps you.
http://www.ericthecarguy.com/faq/solving-automotive-performance-issues
Here are the numbers. I just snapped a picture of the smog form. 2 years ago I had to put in a new cat, so I doubt that’s the problem. I am clueless about smog stuff so any advice would be helpful.
By the look of it you might have several things going on. That said, the article that College man posted is a great place to start. It covers the basics as well as some more advanced tests and diagnosis. Always start with the basics. In the end you may need some expensive parts like a new catalytic converter. I wouldn’t go there until you get the engine running better. If you put a new converter on a badly running engine you can ruin the new converter in short order.
Good luck and keep us posted.
After looking over the posting collage man put up, I am still confused. The issues I have are smog related. I am already going to be doing a full tune up, and since I work in a shop some of the bigger tests I can do there. The problem I am having is I don’t know where to start looking for a problem. The car runs fine. I don’t have any codes. If I had a problem I would actually have an easier time diagnosing it as I can figure out why its failing smog there. The only issue I am feeling is the smog fail.
Granted they said my timing was a little off. I am supposed to be at 15 degrees off TDC plus or minus 2, so being at 17 is within that margin of error.
I don’t have a digital thermometer on hand, or I would test the cat to see if that’s the problem, but if it is bad, why did it fail in 2 years?
see if this helps.
I see that someone circled timing at 17 degrees. If the timing is advanced over spec it could explain the high NOx reading. It also looks like it’s running rich by the high Co reading. I would check the operation of the O2 sensor first of all.
If the engine has an EGR valve you need to check that it’s operating correctly. A problem in that area can cause a high NOx reading also.
I was just remembering my ’92 DSM. By the time that car had 50k the EGR passages were full of carbon.
Many owners hate emission equipment and will pull it. This car being a Prelude I wouldn’t be surprised if the EGR has been removed and blocked off. If true, on a car of this age probably no code for this.
Yeah, that’s one of the things I did two years ago. I took the egr valve apart, scrubbed it clean, put a new gasket, cleaned the throttle body, even cleaning the entire intake before putting it all back together. I even put a new thermostat in there when my radiator blew up from old cracking plastic. The o2 sensor would make, as I haven’t replaced those in the 7 years I have had it.
[quote=”Tarnoth” post=101530]After looking over the posting collage man put up, I am still confused. The issues I have are smog related. I am already going to be doing a full tune up, and since I work in a shop some of the bigger tests I can do there. The problem I am having is I don’t know where to start looking for a problem. The car runs fine. I don’t have any codes. If I had a problem I would actually have an easier time diagnosing it as I can figure out why its failing smog there. The only issue I am feeling is the smog fail.
Granted they said my timing was a little off. I am supposed to be at 15 degrees off TDC plus or minus 2, so being at 17 is within that margin of error.
I don’t have a digital thermometer on hand, or I would test the cat to see if that’s the problem, but if it is bad, why did it fail in 2 years?[/quote]
Engine performance DIRECTLY effects emissions. If your engine is not performing correctly, your emissions will be off. So often I see people overcomplicate the process of diagnostics. The truth is, that most times it’s just a matter of covering the basics. I know you said you were going to do a tune up and that’s a great start, but do yourself a favor and use the correct parts, if not, it may be money wasted. That said, you need to make sure the basic operation of the engine is up to snuff before you go for more complex theories about your emissions problem. Otherwise you’re spending a lot of time chasing assumptions instead of letting the evidence point you to the problem.
I don’t think your timing has anything to do with it but as I said in the article a loose timing belt can effect engine performance and also emissions. As for the catalytic converter you can also check the readings on a scan tool as I showed in the video. Also, the thermometers are about $20 these days and you can find them at most auto parts stores. It’s a useful tool to have in the box for other diagnostic purposes.
I hope that puts a bit of clarification on it for you.
Good luck and keep us posted.
[quote=”JTF” post=101644]Start at the basics. Can you attach a scan tool/fuel pressure gauge and post the data?[/quote]
It’s an obd1 car, so I am not sure the scan tool would work, or even if its able to be hooked up to anything. One of my biggest irritations because I am lacking so much info from the car. As far as a fuel pressure regulator, I would have to check with some of the techs and see if they have anything like that.
Tarnoth: wrote
It’s an obd1 car, so I am not sure the scan tool would work, or even if its able to be hooked up to anything. One of my biggest irritations because I am lacking so much info from the car. As far as a fuel pressure regulator, I would have to check with some of the techs and see if they have anything like that.
Eric is going to have to help you out with that…all I know about Honda’s it starts with an H :blush:
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