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Discussion Starter #1
Here's an interesting issue. About 8 months ago I started running Plus level gas in my 03 Murano SL AWD. I noticed a slight performance improvement and my mpg actually increased as well. I thought it was worth the extra cash. About 2 months into running the better gas (winter time) the check engine light came on. I ran a diagnostic and found a P0420 (catalytic converter, left side i think) code. Thought this was strange and reset it. light was intermittent for about a month. It would come and go without rhyme or reason. It finally came on steady so I took it to the dealer. Dealers response was it looks like a converter but we need to keep it for two or three days. I wasn't prepared to leave it so they charged me $60, turned off the light and I was on my way. Sure enough the light came back on the next day. I lived with it for about 3 months when the price of gas really started bothering me so I switched back to regular. Guess what? The check engine light went out and hasn't been back on since.

Does anyone have any thoughts on this?
 

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Not really.
Hundreds of owners here use mid grade or Premium grade with no problem.
(Hundreds also use regular I would guess)
That by itself cannot be the problem.
The fact that both power and economy improved would indicate that you weren't doing any harm to the vehicle.

The human brain is always searching for patterns.
There is a very good chance that what is happening is random.

Take it to the dealer and get the converter changed out.


Homer
 

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Discussion Starter #3
I did take it to the next step and ran the higher octane again. Sure enough the check engine light came on again. And when I went back to regular the light went out.

I'm a trouble shooter, so when I a problem is repeatable it must be explainable.
 

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Have you been buying the same brand of gas all along? Maybe you should try a different brand of premium.
 

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Clearly your situation is related to the fuel you are using.

It sounds like your engine is not adjusting the timing and consequently, you are not burning all the fuel (higher octane will delay ignition to allow greater compression and more complete combustion). The unburned hydrocarbons are likely fouling the left side cat (the O2 sensors on the front and rear banks are likely getting uneven reading, indicating a rich condition on one side). This could be something as simple as a leaking fuel injector or something like an engine timing issue. Speculation, of course.
 

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Discussion Starter #6
As for different brands of gas I'm on the road 4 days a week and although I try to stay with Exxon Mobil that's not always possible. Lately it's been Shell.

The other explanation makes some sense to me, but why is it only effecting the timing and such with the higher octane fuel?

At this point I'm not going to subject it to the dealer, I'm way out of warranty. I'll run the regular gas and keep movin' on. Thought someone might have a simple answer.
 

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Lower octane gases burn faster, so you ignite them later (retard the timing). Since the Murano engine is designed for 91 octane, the engine will probably ping a little on 87 gas, and the knock sensor will pick up on this. Then the computer will retard the timing accordingly.

When you switch back to higher octane, the timing should be advanced accordingly.
 

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Discussion Starter #8
I probably should have stated before that there was no noticeable difference in the engine, i.e. knocking or pinging. The only reason I started running the higher octane were the comments I read on this forum regarding better performance.

As I mentioned, I felt a slight increase in performance and the computer indicated about a one mile per gallon increase in efficiency.

It's running fine again with regular 87 octane fuel.
 

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cdstrong said:
I probably should have stated before that there was no noticeable difference in the engine, i.e. knocking or pinging. The only reason I started running the higher octane were the comments I read on this forum regarding better performance.

As I mentioned, I felt a slight increase in performance and the computer indicated about a one mile per gallon increase in efficiency.

It's running fine again with regular 87 octane fuel.
I'm not saying that's the problem, I'm explaining how octane affects timing.
 

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Service Engine Soon [SES] Light is on again

Just wanted to chime in and say that I'm going on month two of my SES light going on and then off again.

I talked to my local Nissan repair shop [not the dealer] and they said it's because I'm using the 87 oct gas. They said to bring it in and they would diagnose and provide an estimate for $90 [is that reasonable?].

Seeing that I just got the Murano back from the dealer for the whole air bag replacement thing [$3,000+ to fix] I'm not real excited about taking her back in for work.

Can anyone give me any estimates on what I'm looking at to replace/fix the P0420 error?

Thanks guys.
 

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Re: Service Engine Soon [SES] Light is on again

FlyerNo9 said:
I talked to my local Nissan repair shop [not the dealer] and they said it's because I'm using the 87 oct gas. They said to bring it in and they would diagnose and provide an estimate for $90 [is that reasonable?].
Gee, I wonder why the rest of us who are using 87 octane are not getting the same error?!?! Your dealer is full of it. :bsflag:

-njjoe
 

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Using 87 gas should not trip the check engine light unless you have a bad knock sensor, which should be fixed regardless of what kind of gas you are using. Most likely it is an O2 sensor or evap leak - I would just get the code read for free at Autozone (or any other carparts store - most of them offer this service to sell you parts).
 

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I retrieved the code from Autozone [P0420]. Of course the repair shop, knowing I have the code still wants to diagnose it themselves.
 

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FlyerNo9 said:
I retrieved the code from Autozone [P0420]. Of course the repair shop, knowing I have the code still wants to diagnose it themselves.
Oooh P0420 is a "three way catalyst" malfunction which can be traced to a variety of components - three way catalyst, exhaust tube, intake air leaks, fuel injectors, fuel injector leaks, spark plug, improper ignition timing.

This one is a tough one and would be better to have a professional shop diagnose (hope its an intake air leak).
 

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FlyerNo9-

Your dealer might want to take some time and read the Service Manual.

-njjoe
 

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You may not be out of warranty after all. Remember, there is a federally mandated emmisions control warranty.

Federal law states that if an original equipment component or system of your car fails because of faulty design or a defect in materials or workmanship and the failure causes the car to exceed federal emissions standards, the manufacturer must repair or replace the defective part or system free of charge for a period of five years or 50,000 miles, whichever occurs first. There is no cost to you—not for diagnosis, not for parts, not for labor.
The design and defect provision applies to the failure of all parts and systems of a vehicle whose primary purpose is to keep emissions at or below federal or state standards. Some of these parts and systems include the catalytic converter, exhaust gas recirculation system, positive crankcase ventilation system, early fuel evaporative system, and air injection system.
 

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Thanks Stu but I have over 100,000 miles on my Murano.
 

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FlyerNo9-

As you can see from my earlier post, one of the problems that may be causing the P0420 code is spark plugs. You mentioned you have 100,000 miles on your MO. Are they the original plugs? Nissan recommends they be replaced at 105,000 miles.

-njjoe
 

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I believe the spark plugs were changed at the 80,000 mile check up. I'll have to double check.
 

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Now that the SES light is on again [error code P0420], how long/far can I travel before I cause serious damage to my Murano?

 
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