2002 Nissan Sentra

I’ve been driving my daughter’s Nissan for the past week, trying to figure out what’s going on. Car has about 124K miles. Automatic transmission. Two things happening, neither with total consistency: (1) Sometimes, primarily from a cold start, car will not shift gears. You’ll go past the speed and RPMs where you would have expected the gear to shift, but engine whines on. When you let off the gas, it then shifts. Same from 2nd to 3rd. While in this mode, would not seem to stay in 4th - would briefly shift in (for about a second) , then return to 3rd.
(2) Other item - more frequently, primarily from a warm start, but also from a cold start - car shifts gears at proper time, but there is a distinctive “jolt” as it shifts from 1st to 2nd; not really noticeable in higher gears and the “jolt” can vary in intensity. Almost feels like a broken motor mount, but don’t think that’s it. Doesn’t happen with scenario (1) described above. Also, while in this mode, I noticed, while highway driving, that if I was at the bottom of a long hill, going 60 and floored it, there would be no power surge. It was not downshifting into 3rd like it should. I would have a long and slow acceleration , with the tachometer holding steady at about 2700 RPMs, not climbing as you would expect. But, if I was going about 50, then you would get normal hillclimb acceleration.
My mechanic - whom I’ve dealt with for a long time and trust - had wanted me to drive it awhile and see what was happening before bringing it in. When describing these symptoms to him, his reaction was “Hmmm - doesn’t sound good” but without the quick diagnosis I’m accustomed to from him. Anyone have any thoughts? Thanks in advance

Check The Fluid Level & Condition (For Clarity & No Burned Smell).

Nissan’s got a Technical Service Bulletin (published to help their technicians) for this model-year/make/model.

The one page bulletin (Classification # AT04-002 Reference # NTB04-035) addresses abnormal shifting of auto transaxles (RE4F04B/W equipped) and includes 2000 - 2004 Sentras, so equipped. After running through a little checklist and not finding the problem then the fix is to replace the control valve assembly (valve body).

CSA

thanks, CSA. I will follow-up with checking the transmission fluid level. Follow-up question. Your “burned smell” notation piqued my concern. I have occasionally noticed a “burned rubber” smell especially when I’ve pushed the engine a bit in my test drives. It’s there early, but then seems to go away if I continue driving. Is that a fact of significance?

" . . . a “burned rubber” smell especially when I’ve pushed the engine a bit in my test drives. It’s there early, but then seems to go away if I continue driving. “
” Is that a fact of significance?"
Could be.

Perhaps an engine compartment fluid (transmission fluid, engine oil, etcetera) is dripping / leaking onto the engine / exhaust system while the car is parked and then when the engine starts and heats up it burns off early in the drive.

I’d check all fluid levels carefully and look for any tell tale signs of fluid loose in the engine bay.

CSA