# running rough and stumbling on acceleration



## Guest (Jan 25, 2003)

My wife’s 90 Maxima started running rough and stumbling on acceleration a few days ago. I checked for loose connections, replaced the spark plugs, cleaned the rotor and cap and replaced the fuel filter with not improvement. The computer gave me a code of 51 and indicated a lean running condition so I took it to a friend of mine that has a shop and he confirmed my fear the I needed to replace the fuel injectors. So I replaced them and the car ran great for about 25 miles and now it’s doing the same thing again ( code 51), so now I’ve checked for voltage at each injector and continuity between the injectors and the computer and found them both to be good. Before I go replacing the computer I was hoping that one of you experienced Maxima guys could give me some advice, known problems similar experiences, anything that might help would be greatly appreciated!

Matt <><


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## Ruben (Oct 15, 2002)

I'd check the PCV valve, and O2 sensors.


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## Guest (Jan 26, 2003)

The PVC valve works as advertised and there are no intake manifold leaks

I have no code 31 for the oxy sensor ( could it be bad anyway?)

I have code 51 ( injector circuit) I replaced all 6 injectors and checked the injector harness, it’s ok.

and code 14 (vehicle speed sensor) The speedo has not worked for about a year and a half.

I’m still baffeled! Heeeeeellllllppppp!!!!!!!!

Matt <><


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## Slurppie (Oct 15, 2002)

By chance, have you posted your question here? I know we have added a few new Maxima guys to our member list so hopefully they will chime in soon.


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## Guest (Jan 28, 2003)

I have a 92 VE30DE where yours is the VG30E, but a guy here at work has a VG and he had a similar problem that you are describing. Check out your flex pipe to see if you have any leaks. It may sound crazy but that is what was wrong with his car. That part is notorious for getting holes in it. You can get a new Y-pipe that will replace the whole thing and should solve the problem.


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## nismo1989 (Jan 13, 2003)

cneary812 said:


> *I have a 92 VE30DE where yours is the VG30E, but a guy here at work has a VG and he had a similar problem that you are describing. Check out your flex pipe to see if you have any leaks. It may sound crazy but that is what was wrong with his car. That part is notorious for getting holes in it. You can get a new Y-pipe that will replace the whole thing and should solve the problem. *


Y-pipe? That does sound crazy. I would check the fuel return lines and all other fuel lines. Common problem. Also, listen for injector tick to make sure they are still running properly and it's not a voltage or bad injector issue. To do this the backwoods way (since I'm assuming you don't have a $10K computer like the dealership) take a stethescope and stick a piece of an uncoated coat hanger in the end. Place the wire on each injector and listen for the tick. It should be a nice, uniform beat. If one is off, or not ticking at all, you've come a huge step closer in your diagnosis...

Post back and let us all know what you find.


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## Guest (Jan 29, 2003)

not the y-pipe per say, it is the flex pipe that connects the y-pipe to the cat that gets corroded and cracks. The brading flakes off and the holes get bigger and bigger. When this happens the system sucks air in and messes with the O2 sensors readings which causes the lean burn.


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## nismo1989 (Jan 13, 2003)

cneary812 said:


> *not the y-pipe per say, it is the flex pipe that connects the y-pipe to the cat that gets corroded and cracks. The brading flakes off and the holes get bigger and bigger. When this happens the system sucks air in and messes with the O2 sensors readings which causes the lean burn. *


Interesting.

I don't see how it could be lean enough to cause so many problems to the drivability, though. Sounds to me like his engine has a miss. I don't think all of his cylinders are firing, or at least not all at the right time...

Interesting theory about the flex pipe, though. That would certainly be true, no doubt.


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## Guest (Jan 29, 2003)

now it usually is accompanied by a loud exhaust sound that will get louder and louder! But you would be amaised what a little air coming in from the wrong place can do to a car that relys on computers to run it.


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## Guest (Jan 30, 2003)

nismo1989:
The injectors are ticking well, remember I replaced all six of them.

"I would check the fuel return lines and all other fuel lines. Common problem" I have good fuel pressure but I haven't checked the return lines, could I just blow it out with compressed air?

cneary812:
I' glad you clarified what the Y pipe is I'll take a look at it. I'm no guru but I would think that if extra air was getting in upstream of the O2 sensor it would dilute the exhaust and give the O2 sensor the impretion that the engiine was running lean, the computer would then compensate. The exaust isn't loud eather. But again I'm no brain surgen. 

I'm going to try a salvage computer, I can pick one up for $100, it would cost me that much to have mine tested and then I'll have an extra (plus they'll let me check it in the parking lot before I pay for it.

I do get a speed sensor code sometimes? I'm thinking that why my speedo hasent worked for the last year. So I'm assumeing that has nothing to do with it because the speedo has been out for the last year and it has driven fine all that time.


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## Guest (Jan 30, 2003)

When you are under the car you will see that the flex pipe wire brading will probabally be falling off. You will have to cut this off with a knife or shears to expose the flex pipe itself. Then you will be able to see if the pipe is corroded bad enough. 

My 92 SE has pinholes in its flex pipe, I am going to just replace the whole y-pipe back since the flex pipe is part of the y-pipe. You could cut the flex pipe out and put in a new one but I don't see the point of it when for a few extra bucks you can get a SS y-pipe that will give much better performance to boot.


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## Dwntyme (Dec 18, 2002)

One think you may want too check as well is if the fuel pressure regulator is working properly


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## Spddracer (Jan 31, 2003)

Check this , Under the car at the rear of the flex pipe is a O2Sensor , Unplug it and look in the connector for water , The 89.90;s are notorious for getting water in the 02 connector making them run horrible and can throw the 51 code because of the way it makes it run , I think this is your problem , You can also backprobe the middle wire in the connector and take a voltage reading with the engine warm rev it to about 1500 and the voltage should change back and forth from around 0 volts to 1 volt dc , If it is reading over 1 volt there is moister in the connector and voltage is bleeding over from the heater wire (12 volts that heats the senosr up) in the sensor connector , Check this and I think you will find your problem , also the sensor could just be bad and causing your problem ! Winter is heck on that connector


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## d_warner (Jan 18, 2003)

Clean the throttle body and a new fuel filter?

David


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## Guest (Feb 25, 2003)

Did those to. What it turned out to be was a newly rebuilt BAD fuel injector. 

Thanks for all the help, everyone!

Matt <><


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## Spddracer (Jan 31, 2003)

Ohhhh Rebuilt injectors , That would explain it , I wouldnt put those in my Lawnmower


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## nismo1989 (Jan 13, 2003)

90max said:


> *Did those to. What it turned out to be was a newly rebuilt BAD fuel injector.
> 
> Thanks for all the help, everyone!
> 
> Matt <>< *


That's what I suspected. Did you try the trick I told you or did a mechanic discover the problem? Glad to hear that it's working okay for you now...


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## Guest (Feb 26, 2003)

Yes I did had tries what you suggested with my stethoscope, in fact that’s how I know to change out the injectors in the first place. When I did it again after changing them they all had a good strong ticking. I did finally take it to the dealer for the $80.00 car wash with a diagnostic on the side. They put a pressure gage on the fuel input line and gave the injectors a typical signal and looked for a fuel pressure drop within a given tolerance. I don’t have the equipment to do that at the house. Anyway the parts house gave me another injector and half off on the new gasket set. Took me about two and a half hours to do the job the second time ( the second time is always faster. 

Now I back to my true passion;
93 Grand Cherokee 4X4, V8 318, 32X10.5 BFG’s…… 
1948 Willys V8 283, 33X12.5’s…..

Again thank you all for all the help!
Matt <><


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## nismo1989 (Jan 13, 2003)

90max said:


> *Yes I did had tries what you suggested with my stethoscope, in fact that’s how I know to change out the injectors in the first place. When I did it again after changing them they all had a good strong ticking. I did finally take it to the dealer for the $80.00 car wash with a diagnostic on the side. They put a pressure gage on the fuel input line and gave the injectors a typical signal and looked for a fuel pressure drop within a given tolerance. I don’t have the equipment to do that at the house. Anyway the parts house gave me another injector and half off on the new gasket set. Took me about two and a half hours to do the job the second time ( the second time is always faster.
> 
> Now I back to my true passion;
> 93 Grand Cherokee 4X4, V8 318, 32X10.5 BFG’s……
> ...


Well, glad to know it worked out in the end


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