B16 Sentra transmission Question

[cthreefive]

Hey Guys,

New member, as usual, I come with a question.

Normally I do all my own maintenance on my car and she's pretty well kept (Regular synthetic oil changes, tires, alignments, brakes, coolant flushes etc.)

Cars got about 122K miles on it, and for a few months I've noted that after driving at 50-60 mph and then coming to a stop, the rpm settles to about a 750/1000, but then goes down to about 500 for a few seconds and then "recovers" to 750/1000 rpm, I'm able to notice this (not a giant thunderous shake) but can notice it when it does.

What could be going on?

Its been about 60k miles since I last changed CVT fluid (dealer done), and about 2k miles since oil changes (again, do these on my own, synthetic, at about 5k mile interval).

I'm probably going to get the CVT/Coolant flushed on Friday as well as change the spark plugs, but anything else I need to keep an eye out for? Car's been great to me, and I don't mind dropping some money to maintain her.

Any and all suggestions welcome, again, thanks and great forum!

[benissimo]

Also a new member, only doing cars for a year. I have a b16 manual.

If you go to advance you can get your batt starter and alternator check. I say advance because of the big 3 or 4 stores they have a little bit better test. This happened to me. I first noticed the rpm dip while idling with AC on. That was what was causing mine and the spike in current that it was giving eventually fried my battery, probably only had it a year.

Does the engine ever die when this dip happens? Or does it always recover?

[benissimo]

Also while you're under the hood, a quick air intake check could be nice. Clean throttle body. Check MAF for obstruction (I got a leaf in mine once started dipping rpm and eventually killing engine) and pcv valve. It is on top of engine on the front (pass side by the pulleys). Those go bad all the time and they are 10 bucks.

Change of spark plugs is always awesome especially at 122k but you should probably get a misfire code.

I don't know about CVT since I have the manual. But I would think if you had a sensor issue it would throw a code. I'm sure someone here will be more knowledgeable.

Then there's possibility of fuel issue (injectors, filter) but I think you'd be having progressively worse issues.

If you aren't getting any codes though, I'd almost bet money on that alternator

[cthreefive]

1) Does the engine ever die when this dip happens? Or does it always recover?
I changed my battery about 2 years ago, just died one day (but that was when the care was nearly 5-6 years old, with tons of miles on it.. so i figured that was just an isolated thing.. havent had a problem with the battery since.

2) Ill check out the air intake, mass air flow thing tomorrow as well as PCV Valve.. am i just looking for some dirt/debris that could be obstructing?

So I got the Spark Plugs/CVT fluid changed, didn't really change a whole lot, does still happen after I sustain going 60 mph and then come to a slow/normal halt, itll just go down to 500 rpm and then jump right back up within 10 seconds, but definitely am noticing the vibration now. The guys at the dealership surprisingly stated the multipoint inspection had no faults (I know it doesn't cover internals, but stealership saying your 122k car is perfect.. woah!)

And follow up to fuel injector/filter.. wouldn't that do it all the time, vs. just when going at a higher speed than coming down to a stop?

Also.. no codes. So i'll have to go and get that alternator checked too.. if its that, then it'll hopefully be a easier fix.

Thanks for all the suggestions, i'll post back with what I find!

[centralcoaster33]

Just a thought here, but ground wires are pretty important in cars. If you have a bad connection, you can get all kinds of weirdness, including this kind. So, go around and check that those are on and on tight! You can get your FSM from our Service Manuals link at the top of the page. The EC chapter is all about electronics for the engine. That will show you where all of your ground wires go.

Another typical thing for odd idle is a vacuum leak. Can you check your hoses and intake area for these?

Also, I've glanced it here and there on some forum threads, but there could be a faulty fuel pressure regulator on there. I think there may have even been a recall or TSB on that, but I could be confusing this with the Versa. Similar symptoms though, odd dips at idle with CVT.

http://www.nicoclub.com/archives/use-ni ... abase.html