Can't accelerate up steep hills or over bumps?



I have a 2008 Nissan Sentra with 90-something thousand miles on it. Last summer I moved from Texas to Oregon, so it went through 125° Arizona heat (during which overdrive stopped working for a while) and mountains for the first time. Ever since then, if starting from a parked position, I can’t go over hills or bumps or even curbs. I can IF I was already driving on a flat surface. But if I stop on an incline and then try to drive forward (or reverse up it), I can’t. The RPMs don’t go above ~1.5k until I’m back on a flat surface.

The check engine light is on, and has been on since last summer, but the code it spits out is something dealership specific, so I have no idea what it is (the dealership is going to charge me a hundred bucks just to run their tests). People have told me it “might be something with the transmission”. The problem hasn’t gotten better or worse since last summer, so I just ignored it and got really good at not stopping before steep inclines or hitting curbs or anything (lol). But if I ever need to, I’ll be in huge trouble. I can’t even drive over medium sized rocks if I park too close to them.

The first time I found out about this was when I pulled into a friend’s downhill driveway last summer, and then couldn’t reverse out of it. He had to push it back up. D: Any ideas what this is and how costly it’ll be to fix? It never did this before the trip north.

Note: from a stop, it will go up GRADUAL hills and over SMALL bumps just fine, but anything that takes more than 1.5k RPMs to overcome isn’t happening. It will go up steeper hills and larger bumps (and curbs) only if I was already driving, but it still can’t tackle the steepest mountain road inclines like other cars can.

The 1.5k RPM problem goes away when it’s on a flat surface (or if I started driving on a flat surface before encountering a hill), and it accelerates normally again. However…

It also takes a couple of seconds to rev beyond 1.5k RPMs after stopping at a red light.


Do you mean that when you givei it gas, it will not go over 1500 rpm? If so I think your cat is clogged. This would explain the hills and no power.


Yes, but ONLY if I’m trying to go over a hill or bump from a stopping position. It goes up to 2-3k RPM normally on the highway, for example.


I will throw out a problem with you traction, stability control sensors which control throttle response. This assumes your car came so equipped. *just found out it may not have it.


Does it feel sluggish during normal driving? If you are going up a hill while at highway speed, does it bog down?


@knfenimore‌ It doesn’t feel sluggish driving normally at all. If going up a hill at highway speed, it also behaves normally: RPM increase to 3-4k.

Thanks, @dagosa‌, I’ll double check as well. :slight_smile:


Since you say there is a manufacturer-specific code, I take it you tried a generic OBD 2 reader. Bite the bullet and get a proper reading. You may be risking something expen$ive by ignoring the specific problem.


@NYBo I know, and I totally would, if I had a spare hundred bucks lying around.

@knfenimore‌ Another note: If I slow down and stop on a hill, I won’t be able to continue up it because the 1.5k RPM problem comes back.

Also, after a certain incline (not sure what grade, but it’s very steep) the car slows down altogether and the 1.5k RPM problem comes back as well.


I think the computer may be going into what they call “limp mode” for some reason. This happens when the engine or transmission computer detects a problem that could be damaging to the car to continue to drive with full power. When that condition is detected, the computer limits the amount of power and rpms no matter how much the driver presses on the gas. The idea is to save you from a high repair bill, or causing a condition where the car simply stops running and leaves your stranded.

You should try Googling for a Nissan repair group on the internet probably, they may be able to offer something more specific. Google that code too. You shouldn’t need to visit a dealership to find out what exactly the computer is complaining about. But you may need to find an inde mechanic who has the Nissan specific scan tool. Or at least a more functional scan tool version than you are currently using.


Without a proper diagnosis, you could throw many hundreds of dollars at the car and still not solve the problem. And you already know what you need to do to have a shot at that proper diagnosis.


Looked at Nissan forums and it is going into safe mode and the most likely cause is the Mass Airflow sensor.


@NYBo I do. But I’m one of those poor twenty-somethings, so I was hoping one of you fine people might have heard about this problem before. :stuck_out_tongue:

@GeorgeSanJose‌ That’s an interesting thought. I wonder why it would only do that on inclines though. I didn’t think to Google Nissan repair groups or look for indie mechanics - those are good ideas! Thanks. :slight_smile:

@knfenimore‌ Wow! That all sounds like a foreign language to me, but I’ll get my Google on. Thanks a billion!


Hmm. A MAF sensor error should NOT be manufacturer-specific. Have you had the codes read? They will do it for free at many auto parts stores.


@NYBo Yeah, that’s what I meant in the description. Sorry for the confusion. They read the code, and said it came back as something only Nissan would be able to diagnose. They were as confused as I was/am.


Somehow you’re going to have to find the $100 to get the diagnosis. There’s no way anybody is going to be able to help you without that. As NYBo pointed out, the cost of trying to fix it without getting a diagnosis is probably going to far exceed the cost of getting the diagnosis and then fixing it. It usually works that way.


The abilities of the auto parts store code readers seem to vary a lot. Most around me seem to just do generic OBDII. But I’ve seen people post things online that surprise me. Do this, visit a couple of parts stores for a free code reading. Don’t ask them what it means. Just ask them to show you the screen of the reader and write down exactly what it says on the screen. Make sure to go through all screens if more than one.

Are you at all mechanically inclined? Or do you know someone who is?