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RPMS fluctuate at 80 MPH

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njjoe

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Discussion starter · #1 ·
Today I filled up my tank with Hess premium-grade gas and headed to the highway for a 90-minute jaunt. After a few minutes at 75 mph something seemed amiss. It accellerated strong but when I used the ACCEL button to increase the speed it felt as if the engine was not responding. It hesitated before accepting the speed increase.

When I got up to a cruising speed of 80 on level ground the engine speed would sometimes rapidly fluctuate between 2,500 and 3,000 rpms. If I backed down to 70 mph all was fine. Around town there is no evidence of any problem. The SES light is OFF.

I have 45,000 on the odo, the air filter was replaced at 42,570 miles, and yesterday my MO ran flawlessly.

Any ideas?? (Other than not driving above the legal limit. :rolleyes:)

Thanx, guys.

-njjoe
 
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#2 ·
I assume you are using the cruise control button to accelerate...were you going uphill a little when you were pressing the button? That could cause the high rev...a delay could be expected I suppose...

The level ground scenario is the concern...have you checked your cvt fluid lately?

I like to add that the slightest incline at higher speed could cause the cruise control to push the engine more often to maintain it. Hence the rev flactuation.
 
Discussion starter · #3 ·
nitely said:
I assume you are using the cruise control button to accelerate...were you going uphill a little when you were pressing the button? That could cause the high rev...a delay could be expected I suppose...

The level ground scenario is the concern...have you checked your cvt fluid lately?
Click to expand...
It was a level road; no headwinds; no tractor trailers. It should have been smooth sailing.

-njjoe
 
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#4 ·
When we did our vegas to sf trip last xmas, I found the computer seems to push the engine real hard to get to the desired speed when using the accel. button as compared to my feet stepping on the gas. It seems to exaggerate the reving at times...

Try recreating the problem again...without getting a ticket.
 
Discussion starter · #5 ·
nitely said:
When we did our vegas to sf trip last xmas, I found the computer seems to push the engine real hard to get to the desired speed when using the accel. button as compared to my feet stepping on the gas. It seems to exaggerate the reving at times...

Try recreating the problem again...without getting a ticket.
Click to expand...
nitely-

I appreciate the effort but the rpm fluctuation occurred after my MO reached the 80 mph cruise speed. It does not appear to be a cruise control related issue.

-njjoe
 
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#6 ·
I think I too may have seen a momentary fluctuation from the corner of my eye at times while driving on the freeway but it never happens when I am starring at it!

Sounds like you may have a vacuum loss of some sort. Also is the air intake hose tight? Maybe you will need to go for the recall.
 
Discussion starter · #7 ·
zebelkhan said:
Sounds like you may have a vacuum loss of some sort. Also is the air intake hose tight? Maybe you will need to go for the recall.
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Bingo! I forgot about that. Thanks, z-man.

I need to bring in the MO to have a noisey rear wheel bearing looked at while still under the powertrain warranty. I 'll have them do the intake recall and hope that takes care of it.

Thanx again.

-njjoe
 
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#8 ·
Make sure you get the service manager to ride with you to see your MO is running perfectly fine before they touch the air flow sensor........you know what I mean....

By the way, Phatty McPatty seems to have issues that somewhat resemble yours but he is thinking he might have a grounding problem. Didn't you have a grounding problem some time ago?
 
Discussion starter · #9 ·
zebelkhan said:
By the way, Phatty McPatty seems to have issues that somewhat resemble yours but he is thinking he might have a grounding problem. Didn't you have a grounding problem some time ago?
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Good memory, z-man.

Back in June '06 my MO went into "limp home" mode and the computer showed a C1000 & C1210 code. The mechanics could not figure out the problem, reset the SES light and claimed they would call in the big guns. A month later they called me back in and implemented Service Bulletin EC06-001a which involved tightening two fasteners under the dash. That took care of the problem.

-njjoe
 
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#10 ·
NJJoe,
Your issue sounds like mine. I did get error codes; Both the U1000 and a Speed Sensor error code (can't remember the exact number, 704 or 720 or something). I'll be taking it into Nissan this week and I'll let you know what they find. I'll have them implement Service Bulletin EC06-001a for the grounding issue. I haven't gotten the intake recall performed because the clamps seem tight but I guess I'll just have them do that since the engine has suddenly stalled out recently.

Phatty McPatty said:
For the last few months I've been having an issue that's been increasing in frequency. When cruising, it will randomly rev the engine up, then drop back down to cruising revs. It happens intermittently and without an obvious cause (constant pressure on gas pedal, flat terrain, etc.). Last night I believe the BRAKE + ABS light came on at the same time and the engine went screwy. The warning lights were only on for about a second, then the engine seemed to have trouble transferring all power to the wheels. The engine was reving much higher than usual to get it/keep it moving. This symptom went away after about 30 seconds but the SES light never came on. I know BRAKE plus Battery is dying alternator, but what does BRAKE plus ABS mean?
Click to expand...
This string of unusual symptoms leads me to believe it's an electrical issue at the heart of all of this (for me at least). I'm hoping it's just an overall grounding issue confusing the speed sensor and the error detection system. My mechanic said that speed sensors fail often on at least American vehicles, about every 30K miles, so he wouldn't be surprised if the sensor was fried.

Patrick
 
#11 ·
Mine did that once a few months after I got it, on a long, level straightaway after driving non-stop for about two hours. I pulled over, shut off the car, waited a few minutes, started it back up, and everything was fine and it hasn't happened again.

Hopefully, just a one-time occurrence for you. In my case, it was early morning with some mist/fog present, so I chaulked it up to that.
 
#12 ·
Cryogenix said:
Mine did that once a few months after I got it, on a long, level straightaway after driving non-stop for about two hours. I pulled over, shut off the car, waited a few minutes, started it back up, and everything was fine and it hasn't happened again.

Hopefully, just a one-time occurrence for you. In my case, it was early morning with some mist/fog present, so I chaulked it up to that.
Click to expand...
Same scenario for me kinda... Except it was approx. 3 hours after when we started to drive.
 
#13 ·
Back from the dealer. It had 5 codes; CAN Communication, Vehicle Speed Sensor, Engine Speed Sensor, CVT and some other one. They said it was a grounding issue as we suspected. Interestingly, he said that part of the 45K-mile service is to clean and tighten the ground points in the engine compartment and under the dash. I'd like to see that one in writing. Is tightening the wheels so they don't fall off part of the maintenence schedule too?? Anyway, it drives like new again! (finger's crossed)

UPDATE: Nope, the issue remains. We'll see what else the dealer has up his sleaves...

Patrick
 
#14 ·
UPDATE: 2 days ago on the highway it revved up as if I had put it into Ds and it stayed there. Shifted to neutral, shifted back, still very high revs. I shifted back and forth b/w D and Ds with no change. Going 70, the RPMs were at 3,500 while coasting, and 5-6K if I touched the throttle. At 30mph, it was still holding at 3,500 rpms. Stopped at a light, then it was normal again. Dealer said it was a bad Transmission Control Module (TCM), which is very expensive if out of drivetrain warranty ($800 for the part alone). Luckily it's still under warranty for me. Not sure if this info helps you. If it's still under warranty for you, hassle the dealer until they fix it.

NJJoe, you're quickly approaching the end of your powertrain warranty, I'd have them look at this!

Patrick
 
Discussion starter · #15 ·
Phatty McPatty said:
NJJoe, you're quickly approaching the end of your powertrain warranty, I'd have them look at this!

Patrick
Click to expand...
Patrick-

I just had the intake recall performed, yet the engine RPMs still fluctuate at 80 mph. Obviously the recall had no effect on the problem.

Yesterday I found evidence of a CVT fluid leak. When the MO goes back to the dealership on Thursday for the rear wheel bearing I will have them address the CVT. Fortunately I am three weeks away from the end of the Powertrain warranty so there should be no hassles whatsoever.

-njjoe
 
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#16 ·
Yeah I too got the intake recall done a few weeks back and obviously it didn't help. Got more info from the dealer though. He said that they pulled the P1700 code, CVT C/U. After following the diagnostic procedure, the recommendation was to replace the Transmission Control Module. When asked why there was no SES light, he said a P1700 error will not trigger the SES. As others have suggested, maybe it needs to be in combination with other codes to trigger the SES, like my recurring U1000/U1001 code. Anyway, I hope this helps.

Patrick
 
Discussion starter · #18 ·
Gonzo said:
Njjoe doing the air intake recall...... did hell freeze over or something? :D
Click to expand...
You'll know hell froze over when I report I changed the CVT fluid. :2: That'll never happen.

-njjoe
 
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nitely
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