Engine Revs up while breaking - Nissan Frontier Forum
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#1 (permalink) Old 07-19-2009, 01:09 PM
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Engine Revs up while breaking

I have a 2006 fronty XE 4 banger automatic, I bought used with just under 50K, at what I thought was a good deal. Recently I noticed that when I am driving at 65 mph down a hill and I brake(slowly) to 50 mph my engine revs up and the tachometer goes up between 500 and 800 rpm's. If I tap on the accelerator the engine and tachometer goes back down to a normal range. I am not sure about what is causing this, and I may have to take my truck back to the incompetent people at the dealership I bought it from to take a look at. I have some thoughts on what is going on but I just don't know for sure. Love my truck hate that dealership , help please.
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#2 (permalink) Old 07-19-2009, 01:30 PM
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mine does that too.. think it's something with keeping the speed at where you braked to by downshifting or something.
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#3 (permalink) Old 07-19-2009, 03:21 PM
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If your question is "Is this normal?" The answer is no.
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#4 (permalink) Old 07-19-2009, 03:29 PM
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yes it is normal. your computer is telling your transmission to lock up to use the motor to engine brake down the hill. there are many threads on this so give it a search if you want a little more detail on it.

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#5 (permalink) Old 07-19-2009, 04:22 PM
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Yes, it's completely normal. Yes, it is engine braking. Yes, when your towing, you will notice that your brakes don't have to work as hard, which is awesome! For everyday driving it is a bit annoying though because I'm sure this effects gas mileage.

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#6 (permalink) Old 07-19-2009, 11:44 PM
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I can get it to "auto engine brake" going down a hill if I brake when starting down a hill, but not every time. I've never noticed it at highway speed, I get it often on the hills near me when going 35-45 mph - I'll brake to slow and it'll downshift so that the engine is braking for me, and it will stay in that gear until I hit the gas or brake a lot to make a turn or stop. But again, it won't do it every time I wish for it, only when I hit the brake just right starting down the hill.

Also take note there is no mention of this oh so useful feature in the manual. I think it might be just a computer quirk. Get the right combination of foot braking, engine RPMs, and vehicle speed -- put all this together in a bowl and mix thoroughly. What you end up with is a downshift when you want it going downhill!

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#7 (permalink) Old 07-20-2009, 11:40 AM
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I don't have an automatic on my XE and I missed that in the OP, but aren't we just talking about the trans locking out overdrive in those driving circumstances?
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#8 (permalink) Old 07-21-2009, 07:53 PM
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I appreciate everybody's thoughts on this. I am also leaning towards a computer quirk too. But Supposedly I had a diagnostic done by the dealership in June and nothing was mentioned. I gotta say that Engine braking with an auto transmission did not cross my mind. I also would not think it normal, especially when I am not towing anything. I am gonna dig through the threads some more, and probably take the truck in to the dealership next weekend. In the meantime keep the ideas coming in!
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#9 (permalink) Old 07-25-2009, 12:17 PM
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RPM Stats

Went to town last night. Going over the hill ( a small mountain, actually) I recorded the the following as left my house.

25 MPH at 1600 RPM

43 MPH at 2000 RPM

55 MPH at 1900 RPM

44 MPH at 1600 RPM (as I was entering the Hiway from the on ramp)

62 MPH at 2600 RPM

60 MPH at 2900 RPM (grade became steeper and over-drive kicked in)

65 MPH at 2300 RPM ( reached top of the mountain pass and began braking
for 50 mph zone and this is when the reving up begins)

50 MPH at 2500 RPM ( the "engine braking" has occurred at this point)

50 MPH at 1800 RPM ( a light tap on the accelerator and the RPM goes down)

55 MPH at 1800 RPM ( speed zone has ended)

60 MPH at 2000 RPM

62 MPH at 2600 RPM

55 MPH at 3400 RPM ( I have braked for another car and the truck revs up)

55 MPH at 1700 RPM ( I have tapped the accelerator again to lower the RPM)

So... Any thoughts on this? Bear in mind I have an automatic transmission. Still looking at taking the truck in to be serviced next weekend.
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#10 (permalink) Old 07-25-2009, 01:05 PM
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question

is the increase in RPMs slowing you down (down shifting from 4th to 3rd) or speeding you up (locked in 4th and accelerating)?

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