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Wandering rpm at speed

5K views 53 replies 11 participants last post by  Vintagewannabe 
#1 ·
So I am having trouble finding a solution to this, but it might be a matter of how to word what I am putting in the search bar but here goes.
So this started when I had my drivers side cam position sensor go out. Threw a code, bought a new one from oreillys, installed, thought I was good. So fastforward a couple weeks and as I am going down the road in 4th 5th or 6th whenever I put my foot down the truck will have the rpm wander before taking off. This happens anywhere from about 2500 to 3000. Pedal to the floor and the needle will waver up and down then pick a spot and take off from there. And its not just the gauge because you can hear and feel it.
When I got the truck I had to change the crank position sensor but that was about a year ago.
The truck has a hypertech tuner but that has been on there for months before this and I already tried uninstalling and re installing.
I also warrantied the new cam position sensor and replaced it with no change.
My battery was going out so I replaced that too.
My last idea was that the new sensor was throwing off the opposing passenger side cam sensor so I have a matching pair on their way.
Also have a set of plugs coming because I havent changed them.
 
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#3 ·
Yr, engine, trans & mileage?

Most have far better luck w/ OEM crank/cam sensors as opposed to an auto parts store brand.
 
#15 ·
Most have far better luck w/ OEM crank/cam sensors as opposed to an auto parts store brand.
Yeh, I don't know if it's related to this particular problem or not - But the out-of-the-box reliability of most aftermarket sensors is ABSOLUTE CRAP.

If I had a nickel for every story I've heard about someone installing a sensor he bought at Auto Zone, OReillys or Pep Boys - and then having all kinds of problems with it - I'd be a ballah living on a superyacht in Dubai.
 
#5 ·
You sure that's not a bad clutch? The RPMs should never fluctuate at all while you're in gear, moving at consistent speed. And I'd get some OEM sensors. NTK might be fine though I think OEM is Hitachi in many cases? I'm not 100% sure but I see the best track records with 100% OEM.
 
#7 ·
I personally think it has less to do with the cam position sensors and more to do with the transmission as well. I'm guessing since you mentioned 6th, that you've got a manual transmission truck. It honestly sounds like the clutch is slipping. Do you have any oil leaks under the truck? This is just a shot in the dark, but i have experienced transmission slippage and it's usually more pronounced in the higher gears since there is more load on the driveline
 
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#12 ·
Im not sure how to upload a vid directly. But if I have it at say 2500 rpm and put my foot down, it will go to 3000 then 2400 then kind of take off.
What is the best way to see the clutch? Just through the cover by the slave cylinder?
Oh, that does sound like a slip and then grab on the clutch.
 
#18 ·
Pedal to the floor and the needle will waver up and down then pick a spot and take off from there. And its not just the gauge because you can hear and feel it.
When your engine revs increase, but your driveshaft revs stay the same... it's the clutch.
It's not a sensor, no matter where you bought it or what brand it is.

You should try a pedal free-play adjustment first, but if it's just worn out,
there's not much left to it, so it will very quickly deteriorate from here.
 
#19 ·
I second that as well. That is the most common cause of that symptom in my opinion. Also, faulty sensors result in erratic/dramatic rpm variations. Clutch or slipping auto will certainly be smoother variations. I would think its an obvious feeling in the seat, but maybe not.
 
#20 ·
So my reasoning on hoping that its not the clutch is that it only wanders about 1k rpm instead of flying way up, I can hold my foot all the way down and it will tix it self, and that if I keep it high in the rpm range like doing a pull, it doesnt wander no matter what gear.

On the downside looking into a clutch price had me find the jwt flywheel. So now I want that for the performance. :unsure:
 
#25 ·
you are saying it revs on the tach but no increase in speed correct?

do you also hear the engine rev equal to the reported rpm or does the engine noise not change?

my thoughts

if it revs on the tach and you HEAR it rev but no speed change its clutch.
if it revs on the tach and you DO NOT hear the engine speed up then its sensor getting confused and misreporting the rpm.

edit just saw the vid - its clutch
 
#21 ·
You really need to find a way to post a video or something of what's going on. These symptoms don't really make a lot of sense.

A manual transmission has no slip. Your gears are fixed and you will be at a fixed rpm any time you are going a certain speed in a certain gear with a certain tire size. This can not vary and if it does, the only thing that can cause that is the clutch.

Throw it in 6th gear at low speed and floor it and take a video. Otherwise we are just guessing. The descriptions don't really make sense but theory says the only thing that can be wrong based on what you are describing as slippage would be a bad slipping clutch.
 
#23 ·
Seems to me that's definitely the start of a failing clutch, it slips a little then grabs. When it grabs, it drags the engine back down to the correct RPM and then it starts to accelerate. I've experienced similar behavior in a friend's Miata.
 
#28 ·
Honestly I’d stick with stock (luk) flywheel, Centerforce clutch, and delete the clutch orifice/delay valve.
I don’t think any of it will improve for 33’s though. I just think the CF is a better clutch. The stock flywheel is fine and deleting the orifice will make the DMF and clutch feel less vague to operate.
 
#35 ·
Clutch.
 
#37 ·
Your clutch's slow death is a bit unusual in that most show a couple/few hints - then just die.
 
#41 · (Edited)
You don't have to... But I would. Makes it longer and heavier leaving on. But if you have a nice tranny jack, you probably don't really need to. It's easy to remove anyways. Pic is of an AT.

Gas Art Machine Auto part Wood
 
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#43 ·
I don't think anybody has been successful skipping the exhaust. There is a list of about 20 items to remove the transmission. I'm pretty sure you will need to do at least about 19 of them. I would just follow the FSM guidance. The only thing I've seen people skip is removing the crossmember right under the bellhousing but I'd remove it as well as it gets in the way and will only cause more hassle than the easy process to remove it.
 
#45 ·
Lots and lots of PB Blaster, marinate it for a few days and hopefully they spin right off. An impact air gun would be useful too, if you have a compressor. I love mine.
 
#47 ·
Of course, I had an AT, but I dont remember pulling exhaust. If I did, it would have most likely just been the cats. What I do remember most was the amount of extensions required to reach the top bolts.
 
#51 ·
So my clutch is in and doing great. Soon I will do a full write up in the correct place. The one thing I dont understand is I replaced the master cylinder, and it has this 2in or so dead spot before the pedal starts. It doesn't slip the clutch or anything, just doesnt feel right to me. I thought about putting back the stock one but with its age I was unsure.
 
#53 ·
I would have left the save cylinder alone. It was working fine and pulling the transmission doesn’t affect it, so no real reason to change it. It’s not a failure prone part on the frontier.

you may have air in the line still. What brand did you use? Old Nissan part would be better than practically anything from a parts store. So if you didn’t go oem I would either go back to the old or get a new oem.
 
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