2006 Sentra RPM Fluctuations, Stalling, No Codes


#1

As with many who may turn up on these forums, I’m out of ideas and desperate for some solutions so I’m hoping someone can help me out.

I have a 2006 Sentra that over the last few months on a few occasions (3-4) when driving on the highway would jolt into the next gear.

I figured that was a warning shot.

Last week, the car simply died on me waiting at a light and the dashboard lit up like a Christmas tree. The car did not start again for about a minute. Thankfully, it did. When I drove it home, the car accelerated slightly on its own into the driveway. I took it into the local Nissan dealer. They found no error codes of any kind. They recommended a whole bunch of things that more or less needed to get done anyways but the pertient one is that they flushed and refilled the transmission fluid and replaced the filter.

I’m pretty sure this isn’t a transmission issue but… not ruling anything out. Hoping it is not a transmission issue.

So I took the car home. A week of local light driving with no issues. I got on the highway yesterday to go to a meeting and the RPMs start fluctuating wildly from 1500-3500. I got off the highway and the car stalled out on me three times on the 10 mile or so drive back to the dealership. It did start on those occassions right away.

They claim they’ve had multiple people test driving the car over the last couple of days and no one is experiencing what I did. Still no error codes anywhere.

I absolutely do not feel safe driving this thing on the highway at this point. What do I do? They seem to be at the end of their diagnostic capabilities and short of randomly repairing every single part on a ten year old car that might be causing this seems… silly.

Money’s rather an object right now. I cannot really afford a new transmission (which may very likely not be needed here) nor a new car.

So I’m here sending out a plea to the car gods and their loyal and very knowledgable followers for any advice.

Thank you very very much in advance.

JC


#2

I think you do have some kind of transmission problem brewing probably. The first sign was the jolting into gear. That’s usually an automatic transmission symptom. What your shop did was correct. The rpm fluctuation is likely another sign of a transmission problem, if that happened when the car was in D and the rpms didn’t correlate with the speed of the car. That’s a common problem associated with slipping clutches in the transmissions. Yes, automatic transmission also have clutches.

There is an alternate possibility. The flush/filter change has fixed the transmission. But you now have a wandering idle speed problem unrelated to the transmission. This would be the cae for example if the rpms changed like that when idling in neutral.

If the latter is the case, that is the rpms wander around in neutral, that’s often caused by air getting into the engine which shouldn’t be. The engine is supposed to be airtight, the only air getting in should be from the air filter and through the throttle body. Have your shop check for broken/cracked vacuum hoses and likewise the entire path from the cold air intake to the throttle body.

If that’s all ok, you may have a dirty idle air control, or, if equipped, drive-by-wire throttle mechanism. A dirty or bad MAF could cause this symptom too.


#3

This one is difficult to figure due to the number of possibilities.

When it dies and will not restart have you tried to restart it while holding the accelerator pedal down?

When it dies at higher speed on the road does this occur just as you maybe back off the accelerator a bit or does it happen suddenly while maintaining speed.

Offhand, this could point to an intermittently failing fuel pump or a throttle body/Idle Air or TPS switch problem.
The varying symptoms point in several different directions.


#4

I’m wondering if this has an idle air control valve

Some of the symptoms lead in that direction, especially the high idle and stalling at the light


#5

A parts house listing shows 2 engine options. The 1.8 shows to have an IAC valve and the 2.5 is apparently an electronic throttle body.

Last weekend my Lincoln got pretty loopy with some similar symptoms. The CEL was illuminated, not flashing, and 2 codes were set; a 1504 for an IAC malfunction and a 1506 for an IAC overspeed error. The car ran like garbage and when the codes were cleared they would pop right back up along with the CEL.

I was of the opinion the IAC was not the problem no matter what the PCM was saying and strongly suspected the TPS switch. The TPS and its connector is impossible to access without removing the throttle body. I removed it anyway. The ohmmeter showed the TPS was out of range one way and stone dead the other.

A new TPS doused the CEL and killed the repeated IAC codes. Never a TPS code at any time. Go figure… :frowning:


#6

Thanks for all the advice so far! The first time it stalled out, it did take a minute or two to get it restarted and it did take some additional pressure on the accelerator to get it started up. The other 3 times, it started right up again with no issues.

The service folks did suggest that there may be a faulty fuel pump but this Sentra has always had their fuel pressure issue and it has always taken a little priming to get the pressure up enough to start the car. I never got the recommended fix I’ve seen around Nissan sites because they all say it’s not a perfect fix for the issue anyways and just waiting a few seconds after turning the key to start the ignition has never been a problem for me.

Also, while I could get that done, I do not understand how that would cause the RPM and hard shifting issues between gears that I’ve been experiencing. I’m really hesitant to just start replacing parts. In a ten year old car I could do that forever and never resolve the problem until every single part was replaced.

It’s the diagnosis that seems like the real problem here because there are so many options and no error codes (which seems like it should be a good indicator of where to look? don’t sentra’s throw off error codes like crazy when something isn’t right?)


#7

Unfortunately you have no choice but to start trying new parts. I’d start with the Idle air control valve if your engine has one, and then the throttle position sensor as ok4550 described above.


#8

Your Nissan dealer may not be the best place to diagnose a transmission problem.
A transmission specialty shop is likely to give you a better diagnoses.
Suggest you visit a transmission specialist next. One who has experience with this particular problem who can rule in/out the transmission.

Regarding your question on code/no code, the engine/transmission functions monitored by the PCM have programmed thresholds, pending codes and set check engine light levels. You would think with the problem you have some type of code would be set but apparently not or it was missed in the diagnosis.

A customer complaint with no error and that can’t be reproduced requires more in depth diagnoses such as monitoring /recording of engine parameters.
Some shops are not equipped to do that or customer decides not to continue diagnosis so they are left with recommending changing parts.


#9

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#10

It sounds like you are doing everything you could possibly do OP. You’ve taken it to the dealership, where hopefully they’ve put experienced techs on it, using their Nissan scan tool, and no diagnostic codes. Then they’ve driven the car multiple times, and the techs say the symptom never occurred when they were driving it.

You are correct that in situations like this, replacing parts at random you can easily run out of money before you run out of ideas of what parts to replace.

If I had this problem w/my Corolla, no codes and weird drivability symptoms, and all the routine maintenance was up to date, fluids ok, engine coolant temp ok, throttle position sensor checks out, what I’d do is hook up gauges to measure the battery voltage and fuel rail pressure, and monitor those as I drive the car. I’d be watching to see if something unusual happen with one or both of the gauges when the symptom happens.


#11

Well, the car finally threw a code Friday afternoon. They replaced the crankshaft sensor which seems to have fixed the issue for now. They were nice enough to not charge at all for the 2-3 hours of diagnostics or the fix which I thought was cool. Does that fix make sense to all of your brilliant automotive minds? :slight_smile:


#12

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