[smitty10101]

long story

2005 Altima v6. Everything stock except regular maintenance parts. 125,000 miles on the odometer.
threw a cam sensor code about 6 mths ago, cleared it, didn't return---great.

This Monday went for a long ride in Southern Ga & Northern Alabama. Road was essentially flat, no real hills & definitely no mountains.
Cruise control on, no a/c

Cruise set for about 62/64 mph. Tach would oscillate from 1800 rpm to 2500 rpm. stayed at either setting for many minutes,then jump from one reading to the other and stay there, not swinging back & forth. Terrain appeared to have no effect on the tach.

Questions:
given that it's stock what is a "normal" rpm for 62mph?
Would a worn/wearing cam sensor cause erratic reading?
Am I looking for trouble where none exists?

thks
smitty

 

[d0ugmac1]

Sounds more like transmission issues to me.

 

[amc49]

I dunno............maybe tach issue. You should see a 200 rpm bump high as the car approaches say a hill, even with no downshift you will drop out of converter clutch at any throttle increase, then the rpm drops back the 200 as it locks up again on the other side of hill. Mine with standard ATX does. And converter slip with load on and off varies another 200.

There is no standard rpm for tach at any certain speed as the car can be slowing, accelerating, or staying neutral and all 3 can alter that rpm.

Of course, if the ECM is INFERRING the rpm instead of actually calculating a number that is accurate that could change that. So much software does that now like water temp readings, many of them are faked now.

 

[amc49]

If trans and car stays same speed then you should hear and feel the rpm difference when the tach changes if engine is truly doing it. There is no way one could miss that big a jump in rpm.

 

[smitty10101]

you should hear and feel the rpm difference when the tach changes if engine is truly doing it. There is no way one could miss that big a jump in rpm.

Good point---tach moved but I didn't hear an appreciable change in the engine noise. Movement of tach needle reminded me of an old speedo with a dry cable, except that it (the tach) went back down to a lower reading and then back up & down.

Sounds more like transmission issues to me

Does that tranny need to be serviced @ some interval or is it SUPPOSED to be a lifetime unit? If it is a serviceable unit what expected cost should I be looking at---outside of dealership?

 

[soapmyster]

If the engine Rpm did not change with the needle then it is surely a communication problem.
I am not sure if the tach signal comes from the cam or crank sensor but I would say one of them is suspect.
If you have not replaced the cam and crank sensor I suggest them to be.
There is a oe kit that comes with both sensors.
I only recommend oe sensors.
Considering you did have a cam sensor code I would not be surprised if it is trying to tell you something

 

[amc49]

It can easily be a gauge issue too, all electronic needles have the ability to do it if they break just right. A needle coil has to break to touch and then not, or short coil windings the same way.

If ignition is fine with no missing with smooth idle and easy starting then crank and cam sensors are likely a waste of money.

Trans? There is NO SUCH THING as a lifetime trans. Anybody saying that has rocks in his head.

 

[soapmyster]

It could very well be the gauge itself. A way to check that is to drive it with a scantool hooked up and verify if the RPM shown matches your tach.
If it only happens on humid or hot days I would suggest solder joint in the cluster.
It does not take much to make a false readings when the connection is not perfect

 

[amc49]

X2, no lead solder has produced more than its' fair share of issues in the world today. It tends to crack much more with temperature changes, the lead gave ductility to stop that.