My 2015 got a tune from Ivey probably 10 years ago now, otherwise no changes at all.

I hadn’t driven for about a month and a half since we had all the snow in NYC.

I kept the battery on a trickle charger for the whole month.

today Im on a short road trip. I noticed when first starting the revs stayed very high, much more than normal startup.

while driving, if I went into neutral and went zero throttle, the revs would pulsate between 800 and 2000 a half dozen times.

But the most persistent symptom is, while rolling forward in neutral at like 5 or 10 mph with no brake applied, revs stay up at 1800. If I come to a complete stop where wheels don’t move at all, I’m at 0 throttle, and not pressing the brake, revs drop to 800.

i read a similar thread and the guy ended up finding a brake booster leak. Do my symptoms point to the same? Especially 1800 rpm while rolling but 800 once stopped, both in neutral and no pedal pressure.

 

Sounds vacuum leak ish. Could be brake booster or something else but that's where I would start.

 

Most similar threads are from people who just had some work done. Nothing for me, but I guess stuff can degrade.

Would I notice less braking power with a brake booster leak?

It behaved perfectly normally on the drive back, only 100 miles each way.

 

Yea, vacuum leaks can pop up anytime. I check mine every spring when I take the car out of storage.

I doubt it. A small vacuum leak could cause this and I don't think it would have any noticeable effect on brake power.

Behaved normally as in the idle acted normal and everything?

 

maybe your throttle is sticking and IACV is fighting it

 

Yeah a month ago when I last drove it, it was perfectly fine. I drive it regularly, but I take the subway to work an WFH. Parked it since streets were super salty and nasty for the snow we got in NYC.

@ViciousLSD - RPMs drop as soon as the wheels stop turning. If they're turning, RPMs spike. Both situations in no throttle, no brake, in neutral. Hence why I was thinking the computer saw it was moving so it might be pumping up a dropping brake booster pressure. And if it's not moving, it doesn't think it's needed.

 

was the AC on? is it on Tephra v7?

 

I turned heat off and it made no difference.

Not sure about the Tephra. It was a tune in shop by Ivey, with the AEM intake I've had since the tune like 10 years ago.

 

If its the tune its going to be hard without accessing/logging what you got. I'm no expert and I have my own tune problems. I've had the Tephra before but my recent tuner gave me pre-Tephra version. These files have been copy&pasted for several years I doubt anyone really knows whats in there except the tables they edit to tune. On mine I see a number of "customization" slash remnants of good old times. There's this particular one that I think I can feel kick in. basically with AC on, once I go over 4500rpm and lift and coast the engine rpm will oscillate 700rpm to 2200rpm several times like the ISCV is following 2 different tables, until I'm at 0mph when it stabilizes. Many times the engine will die. Anyway, maybe you can try to reflash yours or maybe time to visit your tuner?