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Question

It's a 1990 Nissan Sentra, and it passed smog with no problems on May 16, 2006. It runs perfectly, doesn't make noise, doesn't leak nothing, my girlfriend and I went in to get it smogged and they said something was interfering...she didn't drive it all that often, hardly ever. Do Catalyic (sp?) converters make noise? Do they affect how the car runs? Could it be anything else at all? We have someone interested in buying it, so we need to get it smogged.

The car makes no noise that would cause suspision for a problem...and it's not that it won't pass smog, they can't start the smog sequence because something is interfering...he told us it may be an exhaust leak?

Insufficient exhaust flow may be what they said...how is that fixed?

Answer 1

Go to a muffler shop and have it fixed. Sounds like the exhaust system may be shot!

Answer 2

Clean oil will go a long way to passing smog. Was the engine fully hot? Look I am a Nissan Master Technician and Interfering? I do not know what would keep the exhaust from the tester other than a big exhaust leak Interfering I only use that term in your timing belt broke and valve "interference" engine bent all the valves... Try another smog station after a oil change and with a hot engine.

Answer 3

Just a WAG...insufficient exhaust flow out the tail pipe?

If that's what they mean, then as previously mentioned...have the complete exhaust system checked

edit>>>An exhaust back pressure test is one way to check flow. Should be about 1- 1 1/2 psi @ 2k rpm. Most likely the cat conv or muffler is plugged somewhat. Or even a large exhaust leak. But what is strange??? and doesn't add up is the fact that you state power, performance and exhaust level noise is normal. You might try going to another test center...{another one of my WAG's}...maybe they are trying to pull something on you???

Answer 4

Then you may want the exhaust system inspected. It could be around the muffler area, as they are notorious to having moisture, and some water built up from the temperature differences in the weather. So, most likely there is some rusting or something going on under there. Which unfortunately is normal. Good luck.

Answer 5

if its the converter it will be just no back pressure or it will turn red hot and if you look at it and it will be glowing . also it will run ruff is the check engine light on? if so clean the E.G.R VALVE first and oxy sensor then it should pass... easy stuff first.

Answer 6

have you notice the power decreasing if it is clogged real bad it won't run and if you can get it to run you'll notice the cataylic converter getting hot like a stove pipe you can see it at night, they run about $98.00if your engine can't breath it chokes!!!!

Answer 7

if they are plugged yes. Thats all its bad you will have issues

Answer 8

WELL THERE YA GO FIX IT!