maxi-milliyon

How do you know if your cat is bad. I have a 97 max and my friend has a 98 and he gets great gas mileage, and I get
heredous mileage his is moded out and mine is almost stock
other than the pop charger. I also noticed a weird smell coming from the stock muffler. My friend said the cat is probably bad. True or False. How long does the stock cat last. If it is blocked up what is the signs. This may explain this weird sound I hear while driving, which I thought was the brakes, bearing, etc. Someone with the same problem in the past Holla at me.


Maxi-milliyon

BigHops99se

I have never had to replace my cat but i have had similar problems that you are experiencing.

1. I at one point was getting horrible gas mileage. Almost like half as many miles as i was getting before. It turned out that the O2 sensor was out and that was causing the gas mileage problem.

2. Then i was driving and i would hear a weird noise that i thought was a bad tire, but it turned out to be a bad bearing in the rear. Can you describe the sound coming from your car? Mine sounded like a "wooo woo wooo" noise and the frequency would get faster as you speed up.

I hope this helps you, but hey if the cat is out then it gives you an excuse for an upgrade.

maxi-milliyon

Thanks for the info. I'll check the O2 senser. I'll try
anything right now. How did you know the O2 was bad. Did the on board computer diagnosis this or was there other signs. I don't want to change this and if this isn't the problem. Did you car smoke or smell funny when it was cold out side. This weird sound Is like a continuous EEEEEEEEE
RRRRRRRRRRRR sound. Sort of like a low cop siren.
thanks for the info.

Maxi-milliyon

vbxmaxima

If you haven't gotten a check engine light, then chances are that you don't have an o2 sensor problem.

The rear o2 sensor is monitored by the ecu, so if its broken and starts giving weird (or no) feedback signals then the check engine light would come on.

If the cat is bad, a smog inspection will tell you right away if you've got a problem.

Good luck!

Daniel B. Martin

To test for a plugged converter, drill a small hole in the exhaust pipe right before the catalytic converter. Install a temporary hose fitting and attach a long rubber hose and a 0 to 10 pound pressure gauge. With the gauge inside the car, drive up a hill or accelerate and read the pressure. Normal is 2 to 3 pounds, restricted 4 pounds or higher. The drawback to this method is the small hole will need to be welded shut after the test; a minor job if you have a welder.

Daniel B. Martin

The "rotten egg" smell is coming from the Cat, but is not caused by the Cat. It is a sign of an over-rich mixture. The Cat is doing its best to deal with unburned fuel coming from the engine.

An over-rich mixture is consistent with your poor gas mileage. It could be caused by
- "tired" Oxygen Sensors
- fuel injectors sticking open
- obstructed fuel return line
- bad fuel pressure regulator

97GLES

iTrader: (5)

what did it cost u to repair the rear bearing. i think i have the same problem.

maxi-milliyon

Thanks fellas, the exhaust does seem to smell really rich.
I never changed the PCV valve or fuel filter since the car was bought(97 Max 40k). Would these also cause the problem. I'm afriad when I take the car to the dealer they are going to charge me for a whole lot things which isn't the problem, and money is a little tight right now.

Maxi-milliyon

Daniel B. Martin

Problems with these parts are unlikely to cause an over-rich mixture. However, you should get the over-rich mixture problem diagnosed and fixed. The bad gas mileage is costing you money at every fill-up. The over-rich mixture puts an increased burden on the Catalytic Converter, causing it to run hot and "die" sooner. In the extreme case an overheated Cat will catch fire.

You have posted many questions on this forum. Other forum contributors have freely given advice. However, you should realize that advice given by people who have never seen or heard or driven your car is not a good substitute for an in-person diagnosis made by a skilled technician.

Dealers have a high overhead and tend to charge more than independent shops. Ask your friends, neighbors, coworkers for recommendations. Perhaps you will find a former Nissan dealer technician who has opened his own repair shop. That's a good man to know!

maxi-milliyon

I'm always thankful for the information that I receive here,
and I learned in life that what you do to people will alway's come back to you, weither bad or good. Someday you will not know something and someone will help you. And may be the information I learn, I can pass on to another newbie with same problem. This is why we are here. This is the science of life. Big ups to all those on the board that is keeping it real.

Maxi-milliyon

krazydutch44

The day I got my 99se I've been having a rotten egg smell whenever I drive hard. When I went to the dealer a few months later they blamed it on the stillen intake. What do you think the problem is. I switched gas brands 3 times and no luck.

Daniel B. Martin

I doubt the Stillen intake has anything to do with that bad odor. Unfortunately, some dealers are reluctant to do warranty service and will use any kind of excuse to avoid it. If a dealer has that attitude and he sees any kind of modification, he will blame the problem on the modification. You may have to re-install your factory intake, at least temporarily.

The "rotten egg" smell is coming from the Cat, but is not caused by the Cat. It is a sign of an over-rich mixture. The Cat is doing its best to deal with unburned fuel coming from the engine.

An over-rich mixture could be caused by
- "tired" Oxygen Sensors
- fuel injectors sticking open
- obstructed fuel return line
- bad fuel pressure regulator
- bad Engine Coolant Temperature Sensor

It is true that some fuels contain more sulfur than others. However, I think you have eliminated that possibility by changing gasoline brands without affecting the symptom.