[bcaban]

My 01 Sentra has been shaking, then stalling for a couple of weeks. When I brake the car sometimes shuts down. I just had my fuel pump and filter replaced yesterday and I had 2 oxygen sensors replaced. Any other ideas on what this problem could be. I am also experiencing lack of power when I accelerate.

[TxGreaseMonkey]

Replace spark plugs, distributor cap, rotor, and air filter. Check ignitor and coil--AutoZone can do this for free.

[this8384]

What determined the fuel pump and oxygen sensors to be in need of replacement? Is your check engine light on?

[CaptainRich]

On a car that's going on seven or so years of service, what has the maintenance history been? How many miles? Any vacuum lines disconnected or damaged by time?

[ghoust25]

What I've herd so far just a guess chek your oil dip stick and see if it is clean oil or milky looking if it is the head gasket or the head is cracked that will couse a lot of your problems if the check engine lite is on take it to auto zone and thery can put it on the computer for free it thakes about 3min to do but it has to be a 1995 model of newer

[bcaban]

My service engine light went on about a year ago. The shop that I took my 01 nissan sentra to stole my money. They told me it was the catalytic converter when it was just an oxygen sensor that I needed. I found that out after going to a 2nd shop when the light came back on the same day the converter was installed. The scanner is reading the codes po430 and po420. I replaced 2 oxygen sensors, I have 4 sensors total and my service engine light is still on reading the same 2 codes. My car is driving rough and chokes a lot. When the car warms up and I brake there is a shaking as if the car is going to shut down. There are times that it does shut down on the road. Starting it when the engine is already warm has the same effect. I have noticed that I don't have the same power when accelerating either. I'm so lost now so any advice would be greatly appreciated.

[this8384]

Those 2 codes are related to catalyst efficiency of the catalytic converter. You didn't need the oxygen sensors.

How many miles are on the car, and have you ever had a complete tune-up done? I had a woman go 140K+ without ever doing a tune-up; she ignored the misfire that her car had and ended up damaging the converter as well.

It's also possible that the converter that was installed was bad from the factory. It's rare, but I've seen it happen.

[bcaban]

I have brought my car to 2 other mechanics and they have told me that there is nothing wrong with the cat converter. I don't know if the light is still on because the cat converter is not a factory one but the light will not go off. I had a tuneup about a year ago and I have 160k miles now. I check my fluids and they all seem good. I don't know why the car keeps stalling and shutting off.

[Majoria]

There's something missing here.

P0420 and P0430 are determined by the downstream O2 sensors which determine the effectiveness of the converters. The first thing a technician will look at is the effectiveness of the converters by monitoring the sensors and performing an exhaust backpressure test.

I've seen the downstream sensors fail but they rarely have a big effect on the engine performance like an upstream sensor. I haven't worked on Nissan's in a while but I wouldn't think they would be that much different.

Only possible thing I can think of is something unrelated to these codes is causing the issue but won't set a code. I just can't shake that exhaust blockage possibility and mainly from the converter. However, the car shakes when braking as if going to shut down? Long shot possibility of the torque converter clutch sticking (if equipped with an auto trans).

There's some piece of unknown data we're missing here. A bad tank of fuel could have coated the converters.

[ghoust25]

If u have replased the o2 and the lite is still on some times the codes whont clear u havet to get them cleard from the computer auto zone if u have one can do this for free

[bcaban]

My service engine light has been on for a year. After the mechanic put in my cat converter I had to keep going back because my light was still on. He refused to repair it any more so I had to go to 2 other mechanics. Both, told me that it was only a sensor problem. I tried resetting the service light but it keeps coming on. I changed the 2 sensors that were located after the cat converter. Is it possible that the 2 sensors before the cat need to be changed as well. That is rare that all 4 would need to be changed isn't it? I just started experiencing the shaking and shuting off about 2 weeks ago.
I hear a cranking sound when the car is about to shut down and then it just shuts off. It doesn't shut off when the car is cold. Is it possible that it could be a leak in the intake manifold.

[this8384]

There is the possibility of a vacuum leak; however, I haven't ever seen a vacuum leak cause a catalyst efficiency problem.

You don't need a factory convertor; an aftermarket one is fine. Are you 100% positive that the 1st mechanic actually replaced the converter or are you taking his word for it? It's very possible that he charged you but never actually did the work. It sounds like you still need a converter if the same codes are coming up time and again.

Also, how are you resetting the light? Contrary to popular belief, disconnecting the battery doesn't work in this day. You need to manually do it with a scanner.