# '07 Nissan Altima 2.5



## Rokaro (May 16, 2016)

Hi! I recently purchased an 07 Nissan Altima 2.5 S, from a private owner. The car ran great for about the first month and a half, but after that, when I would go on long trips, it would randomly decelerate. And still does. I've replaced the catalytic converter to see if that would help, but it is still giving me the same issue. It will run fine for about 1 1/2 to 2 hours going 75-85 mph but after a certain amount of hours/miles, especially uphill, it's like the car completely loses power. Any thoughts of what it could be?


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## Car guy (Mar 31, 2016)

Ignition.

How many miles do you have on your iridium plugs? Original COPs?

P.S. Presume you checked for codes. What did your sensor data show?


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## Rokaro (May 16, 2016)

Car guy said:


> Ignition.
> 
> How many miles do you have on your iridium plugs? Original COPs?
> 
> P.S. Presume you checked for codes. What did your sensor data show?


I forgot to mention that the car started doing this (losing power) recently. I'm not sure the iridium plugs have ever been replaced, honestly. And nothing came up from my sensor data. I've taken it to several different mechanics, all suggesting a different answer, none of which are write. If I keep the mph at around 60-65 the whole trip, it doesn't lose power though. I did stop every hour just to be on the safe side though.


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## Rokaro (May 16, 2016)

Rokaro said:


> Car guy said:
> 
> 
> > Ignition.
> ...


*right, my bad.


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## Car guy (Mar 31, 2016)

<I'm not sure the iridium plugs have ever been replaced, honestly. And nothing came up from my sensor data. ...>

Maintenance interval is 105k ...

<but after a certain amount of hours/miles, especially uphill, it's like the car completely loses power. ... >

CVT ? (revs/well after operating temp ...) 

Nissan has been replacing CVTs by the thousands (and that may be an order of magnitude low ...)


What's the car's mileage (or mileage when it started the symptoms)?


Worth checking the battery V (alt) as soon as the symptoms recur. (again, revs, temp, etc.)


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## Rokaro (May 16, 2016)

The car started doing "it" around 158,000 miles. And when it does start decelerating, if I wait to let it sit for too long, it won't hardly accelerate at all if I'm at a stop. The car also has a rotten egg/sulfuric smell about it. And it seems to consume an unusually large amount of gas. I filled it up yesterday and it's already at half tank today, no leaks though. I've heard there are two catalytic converters on Nissan Altimas, and like I said, I did replace the manifold and converter. I did reset the computer the one time it started acting up and it seemed to help, but I also let the car sit for about a half hour. 





Car guy said:


> <I'm not sure the iridium plugs have ever been replaced, honestly. And nothing came up from my sensor data. ...>
> 
> Maintenance interval is 105k ...
> 
> ...


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## Rokaro (May 16, 2016)

Also, if it was the CVT, wouldn't I notice it pretty much right away? Because nothing happens unless I'm on the road 90+ minutes going 75-80 mph



Car guy said:


> <I'm not sure the iridium plugs have ever been replaced, honestly. And nothing came up from my sensor data. ...>
> 
> Maintenance interval is 105k ...
> 
> ...


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## Car guy (Mar 31, 2016)

Sounds like it is running rich contaminating the cats, which are getting bodaciously hot as you drive. Diagnostics are in order and would confirm this. Besides, you don't want to get in a cycle of replacing cats when those are not the root cause.


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## Rokaro (May 16, 2016)

could the atmosphere effect what you think it might be? It was in the 90s over the weekend and the problem started within an hour of me being on the highway.


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## Car guy (Mar 31, 2016)

Rokaro said:


> could the atmosphere effect what you think it might be? It was in the 90s over the weekend and the problem started within an hour of me being on the highway.


Yes, on your question. But, I'm not sure I've been much help. Sorry.

There are things I would have done to try to diagnose and isolate the car (study the scan data - if you have that from a real-time run you could post it here or even if you have that from a static car-off capture you could post it here - focusing on the O2 data and FTRMs; replaced the plugs IF in doubt as to them ever having been changed now being 158k - with NGK and same type per OM; checked my CVT fluid for condition and full - supposed to be flushed every 30k miles ... and even then they're going out - huge #s of CVTs are being replaced; checked coil wires for snug; checked for vacuum leaks; etc.)

There are other guys on the forum who may have encountered this.


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## rogoman (Dec 16, 2004)

Rokaro said:


> The car started doing "it" around 158,000 miles. And when it does start decelerating, if I wait to let it sit for too long, it won't hardly accelerate at all if I'm at a stop. The car also has a rotten egg/sulfuric smell about it. And it seems to consume an unusually large amount of gas. I filled it up yesterday and it's already at half tank today, no leaks though. I've heard there are two catalytic converters on Nissan Altimas, and like I said, I did replace the manifold and converter. I did reset the computer the one time it started acting up and it seemed to help, but I also let the car sit for about a half hour.


Perform an ECU code readout with a portable scan tool to see if any fault codes are set. If you don't have a scan tool, most auto parts stores will do the scan free of charge. Post the actual code here on the forum. Since the car has 158,000 mi on it and you're not sure how old the plugs are, I would replace them. Use only NGK OEM DILKAR6A-11 platinum tipped type. Using aftermarket plugs such as Bosch will cause driveability problems.

Check the fuel pressure, in particular when you're having the problem. Tee-in a temporary fuel pressure gauge at the fuel tube. The readings at idle should be: 51 psi.

If you're having a problem with the engine running too rich, the A/F sensor 1 may be marginal; it's located at the top of the exhaust manifold pre-cat. The signal from A/F sensor 1 indicates whether the mixture ratio is RICH or LEAN compared to the theoretical value. The signal then triggers a reduction in fuel volume if the mixture ratio is rich, and an increase in fuel volume if it is lean.


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## Car guy (Mar 31, 2016)

Rogo, he had said he had no codes, for info.


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## Rokaro (May 16, 2016)

I'm going to get it scanned tomorrow. There are not check engine lights on so I wasn't sure if a scan would be any help but it's worth a shot. I'll post what it reads on here, if it reads anything.


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## Car guy (Mar 31, 2016)

Yes, the ECU (scan) data WILL help. If you can post the entire set here - all the parameters, we all can assess for you.


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## Rokaro (May 16, 2016)

Bad news! The scan didn't read any faults whatsoever. Everything was good according to them. I honestly don't know what the next step would be. Any ideas? I'll replace the iridium plugs but it's hard to tell what's helping since the problem doesn't pop up unless I've been driving awhile or unless it's extremely warm outside.


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## Rokaro (May 16, 2016)

Another thing, when the problem starts, at one point, I can press the gas as much as I want and although it won't accelerate, my RPMs still go up like they normally would if I were to accelerate quickly and my engine will rev up, but it won't go any faster. One person had said that Nissan Altimas don't have a transmission coolers and he had to get one installed because his car was experiencing the same issue


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## Car guy (Mar 31, 2016)

<The scan didn't read any faults whatsoever.>

Need to move beyond the absence of codes.

<Everything was good according to them. >

That would be surprising if that were true/accurate.

Again, diagnostics of the ECU data parameter set would help us help you. Have someone scan (all) those values - preferably when the car is running and producing the symptoms, upload it to/for you, and then post here.

<I can press the gas as much as I want and although it won't accelerate, my RPMs still go up like they normally would if I were to accelerate quickly and my engine will rev up, but it won't go any faster. One person had said that Nissan Altimas don't have a transmission coolers and he had to get one installed because his car was experiencing the same issue>

Engine running, but CVT is not.

Your car DOES have the CVT cooling lines. You should see 2 rubber hoses from the CVT to the bottom of the the radiator. One is output hot CVT fluid NS-2 flowing to the radiator for cooling, and the other is the return hose back with the NS-2 slightly lower temp.

Again, Nissan is replacing CVTs by the thousands ... if not tens of thousands ...

Keep us posted.


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## Rokaro (May 16, 2016)

If Nissan is replacing the CVTs by the thousands, would that be a recall?


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## Rokaro (May 16, 2016)

Also, I'm getting it rescanned. ECU scan this time. I'll post what that reads when it's done.


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## Car guy (Mar 31, 2016)

Rokaro said:


> If Nissan is replacing the CVTs by the thousands, would that be a recall?


No, most are being handled under warranty. 

Nissan extended the warranties on many of the cars. 

It had been 5 years/60k miles. It was extended to 10 years/120k miles.

They know about the issues.

They even have a dedicated phone in center just to handle the CVT issues.

With your engine revving and you not getting the power output through the tranny, that would include anything from the torque converter all the way through the CVT to the diff.

Check your records to see if Nissan Customer Satisfaction mailed you the letter for the extended warranty for your car. There was a small tear-off sticker/card in the lower right of the letter to keep with the car for the eventualities.


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