2005 Prius- Mountain, losing MPH on ascent! (no warning lights)

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by MCPriusTexan, May 30, 2021.

  1. MCPriusTexan

    MCPriusTexan New Member

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    Hi there,
    I have a 2005 Prius with 93K miles (just had 90K checkup 3 weeks ago at 91,400 miles) - I've never had problems with my Prius, 2nd owner and have had it 6.5 years.

    I live in Nevada (and drive mostly southern Nevada and California) but drove 10 hours from near Duck Creek Village, Utah, to a half hour north of Denver, Colorado 2 days ago on I-70 (traveling West to East)... mostly at a slight decline the entire trip from Grand Junction, CO to Golden/Denver, CO. But there were about 4 times I had to go slightly uphill for longer than 30 seconds or so, (including near the Eisenhower Tunnel) and I felt panicked bc I would start the ascent going 65-70 but would lose MPH every few seconds. One time I noticed I started at 59 MPH and ended at the "top" 2 minutes later at 37.

    For the return, I had planned to drive the East-West direction on I-70 in a month. And I can't sleep thinking that most of the trip (for the 3.5 hours between Golden and Grand Junction) will be mostly uphill, with only small flat parts. My dad suggested I sell my car and buy a different one to drive back... but that isn't an option. I could try to go south on I-25 through Albuquerque and back across Arizona to Nevada. Or up to Wyoming over on I-80, but I have never driven I-80 or I-25 and so I don't know if I will have problems on those roads. I planned to go through Utah again as I have a place to stay there for the night before getting to Nevada.

    **Also- I usually use regular gas, and based on what I read here, I am happy to refill the tank with Premium (presumably a higher octane).

    **Also I read to keep pressing the gas and don't take your foot off- but when you have near constant mountains and ascent for 3.5 hours, you will need to pull off and get gas at least once. So its not possible to keep your foot on the gas constantly for that period of time.

    I have read the forums here the last couple nights and YouTube videos etc, but would love some advice. I do not want to hurt my car- and I recognize I do not completely understand the consumption and energy visuals, but I assume there is some solution other than driving 35 MPH and upsetting everyone on the road.

    Please help! I will go down through Albuquerque if I have to- but it changes the timing of my trip a lot and impacts my work schedule so I would love to go back on I-70. (I know its the highest interstate in the US).
     
  2. bisco

    bisco cookie crumbler

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    there really isn't a solution to an old car losing power. you're probably gonna need a new battery at some point.
    pump up the tires to 50psi and throw everything not bolted down overboard. and if it is bolted down, unbolt it
     
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  3. rjparker

    rjparker Senior Member

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    No codes? If not you should be able to keep mph up. Not by pressing the gas all the time but by pressing it hard enough to keep your 60 mph. Remember your hv battery won't directly help after a period of time, lets say ten minutes. A continuous ascent means no regen. After a relatively short period, the engine has to provide all the power necessary to move the car and also add a little charge to the hv battery. The hv battery does more than give you hp. It runs all electrical loads, your ac and it charges the 12v battery. The Prius engine has the power to do both things as you are climbing for hours.

    But the engine will rev up a lot as the cvt changes ratios to enable the hill climb. A sure test is to use your cruise control set to sixty. The engine will rev high but will maintain the speed. That is normal. I find I can do a better job than the cruise control relative to the rev noise with my foot modulating the gas pedal.

    If yours can't do it on cruise you likely have a clogged catalytic converter. But I would expect codes.
     
  4. MCPriusTexan

    MCPriusTexan New Member

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    Thanks @rjparker. Where would codes appear? (Sorry for the basic question. I do not have any errors popping up anywhere, so I am not sure if there is a place to see/find codes if no alarms/signals are going off anywhere). All I know is that going up the longer stretches of hills/mountains, which is something I do not normally do in Nevada/California- as I only have stretches less than 30 seconds of uphill and only lose a few MPH on those- but on these longer stretches, that are several minutes, I am going down from 65 to 38 and do not know what I am doing wrong. Wondering if there is something to monitor on the energy/consumption monitor that I do not know about?

    @bisco- I think the Prius has 2 different batteries and I know I did replace one for a couple hundred dollars about 4 years ago.
     
  5. jerrymildred

    jerrymildred Senior Member

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    Welcome. A couple observations.

    If this was your first time at 11,000+ elevation, the loss of engine performance can be shocking. And the Gen 2 Prius isn't exactly a hot rod to begin with.

    Second, it's not even close to a decline from Grand Junction to Denver. For one thing, Denver is about 1,000 feet higher than Grand Junction. Most of the way heading east on I-70 is uphill till you crest Vail Pass at over 10,000 feet. Then a little down before you climb to the Eisenhower Tunnel at 11,200+ feet. That puts you 175 miles from Grand Junction. From the Tunnel, it's only about 65 miles to downtown Denver and it's a drop of 6,000 feet from the tunnel. The grade going up to Eisenhower Tunnel is particularly grueling because it's relatively steep and there's very little oxygen.

    Here's a quick elevation profile I made from Google Earth. Ignore the sharp spikes. It would have taken me forever to precisely follow the road, so the path took some shortcuts. :) Grand Junction is on the left, Denver on the right.
    Screen Shot 2021-05-30 at 8.52.37 PM.jpg

    I have never driven a Gen 2 Prius in Colorado, but I'd think it should be able to handle those slopes. My Prime is advertised as having about the same horsepower. It handled the passes fine with the cargo area and backseat clear full and the two of us in the front. I didn't floor it; I just drove like 50-55 mph right up the road. Ignore the consumption and energy visuals. Just drive it.

    It's also possible that even with the recent checkup, there could be an issue that keeps the car from producing full power -- assuming your right foot is demanding full power. Lots of people drive Prii over those passes.
     
    #5 jerrymildred, May 30, 2021
    Last edited: May 31, 2021
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  6. MCPriusTexan

    MCPriusTexan New Member

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    @Jerry! I have been trying to find an elevation map like that- thank you! So my sense was wrong? If I made it from Utah through to Denver on I-70, then I was going up a lot- gradually- and while the reverse looks a bit steeper to start, its also probably a steep climb for an hour but more of a descent after Eisenhower?

    So the question I would find out early on in the reverse drive- can I make it from Denver to Eisenhower Tunnel... if not, I guess I would have to turn around and Plan B (I-25) the next day...

    **Do you think driving in B would help? (I don't because I think that is mostly for going down the mountain).
    **Do you think moving from regular gas to either Plus or Premium (higher octane) would help?

    Thank you!
     
  7. MCPriusTexan

    MCPriusTexan New Member

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    (And yes- definitely first time with Prius at 11,000 elevation! Or at any real elevation! I was struggling on the road the day before from Cedar City to Duck Creek Village, Utah, to be honest- but the speed limit is slower there (UT-14)
     
  8. fuzzy1

    fuzzy1 Senior Member

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    Higher octane won't help produce any more power, unless you have other engine problems causing it to retard the timing to prevent knock or detonation.
    There is no place on Earth where you will be continuously ascending anything steep for anywhere near that long.
     
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  9. MCPriusTexan

    MCPriusTexan New Member

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    @rjparker, should I NOT run the AC when I am climbing the mountains (if I don't need it). I want to do anything to help the climb and the HV battery....
     
  10. fuzzy1

    fuzzy1 Senior Member

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    When climbing up any significant hill at any significant speed, B mode is identical to D mode, except that B locks out cruise control. The meaningful difference is on the downhill side.

    It seems that numerous flatlanders have always had troubles with Gen2 Prii in the Colorado mountains, but plenty of local residents have not. I don't know how much of the difference has been mountain driving skills vs problems with individual cars.
     
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  11. rjparker

    rjparker Senior Member

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    Codes appear on a scanner but you would normally get a check engine light with them. Gas and B mode makes no difference. You can run the AC. Don't worry if the engine makes more noise to maintain speed. That is normal. Gas mileage will go down as you ascend. That is normal.

    Have you tried to press the accelerator down hard to keep up speed? This is important to know.
     
  12. MCPriusTexan

    MCPriusTexan New Member

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    @rjparker - re pressing the accelerator down hard to keep up the speed- to be honest, I have not. I have had experiences on smaller hills and mountains where I was losing speed, but I didn't press down hard - usually I think (I am not certain but I think what happens is) I apply a bit more pressure but then have actually let up before reapplying pressure. On my drive through Utah (probably 5-6 times) and then on I-70 the next day in Colorado (again probably 5-6 times), when I was losing MPH on the ascent, I believe all the times, I tended to apply a bit more pressure (sort of to verify "am I really losing power while pressing the gas?") but then within a couple seconds, take my foot off the gas and slowly reapply, just because I fear of applying pressure too much - maybe I would burn up the engine or battery- and so I think I take my foot off.

    That said, I thought in the next few weeks before driving back on I-70 and attempting Eisenhower Tunnel again, I would try to do some local drives where I there are ascents and I can try applying continual pressure while I am losing power and see if holding to the pedal helps. I keep thinking my transmission is going to fall out or the engine...

    Thanks for all the help- I really need it!
     
  13. fuzzy1

    fuzzy1 Senior Member

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    If you don't have the gas pedal pressed down as far as it will go, then you really have no basis to complain about it climbing too slow.

    The Gen2 needs almost all the power it can possibly produce in order climb the top of I-70 at speed. If you refuse to give it all that gas, but half-starve it at some mid-throttle position, then OF COURSE! it will lose speed. It takes a lot of power to climb high elevation steep mountain grades at highway speed. But Toyota did build that Prius with enough horses to do it. If older ones just can't do it anymore, then they have built up some sort of problems with age.

    Maybe this is why I've seen so many complaints from out-of-area drivers over the years, but various local drivers keep chiming in that they didn't have such difficulty. They knew what it takes, and were not afraid to apply it.
     
    #13 fuzzy1, May 31, 2021
    Last edited: May 31, 2021
  14. dbstoo

    dbstoo Active Member

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    It sounds the the stereotypical reaction of a new driver to the sound of the engine.

    In a "normal" car the engine speed is directly related to the speed that the wheels turn. We've all learned to listen to the engine to keep a steady speed. The Prius is not like that.

    In the Prius, the speed that the engine spins has nothing to do with the speed that the wheels spin. The gas pedal is not even connected to the engine. I like to think of the gas pedal as a "way to suggest to the car that you want to go faster or slower". The car then adjusts the engine and the electric motors to provide the most efficient combination of power to move the car at the the speed you want to go.

    NOTE: the car will never let the engine over rev, nor will it let the electric motors run too fast. The 2005 is limited to (if I remember correctly) 103 MPH by the computer, not by a lack of power.
     
  15. jerrymildred

    jerrymildred Senior Member

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    How can you expect to maintain speed going uphill if you're afraid to use more throttle? I don't care what kind of car you're driving, it takes more gas to go 60mph uphill than 60 mph on level ground. A LOT more. Like I said before, just drive it. It's not made out of crystal. It's the most dependable car in the world.

    The only thing to be at all concerned about is to keep an eye on your oil level. Any car that age with 100k miles on it will tend to burn oil faster when it's working hard. Just check the oil every tank the same way you should do in normal driving anyway.
     
  16. jerrymildred

    jerrymildred Senior Member

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    Sorry, I missed this in my reply a few minutes ago. It's already been pretty well handled by others, but since you asked me ...
    I didn't find the map, I made it from Google Earth. Actually, I looked first. But even without it, iirc, the city limit signs in CO all give the elevation and so do the maps. Same with the mountain passes.

    Yes, it's a more abrupt climb from Denver to the tunnels, but still no problem. Of course the Prius can make it. But you have to let it make it. Not giving it enough gas really hinders.

    As mentioned, B would not help. It has nothing to do with making more power without burning more gas.

    Premium, if anything, will give less power. Premium has more of the stuff in it that hinders pre-ingnition and therefore less of the stuff that actually burns.

    To repeat, if you want to lift something faster (ie. drive from 5,280' to 11,200' in an hour rather than two hours) you need more power. 1 horse power = lifting 550 pounds 1 foot in 1 second. Want to do it in half a second? You need 2 horsepower. For twice the HP, you need roughly twice the fuel. For twice the fuel, you need to push the gas pedal down twice as far. The car will do it, but you have to tell it to do it. The only way to do that is with your right foot. ;)

    I just spotted this:
    "Wondering if there is something to monitor on the energy/consumption monitor that I do not know about?"
    Ignore that thing. You're letting it scare you. Look at your speedometer. If it only says 38 and you want 60, what do you do? The same thing you do at home: press harder on the go pedal.
     
    #16 jerrymildred, May 31, 2021
    Last edited: May 31, 2021
  17. sam spade 2

    sam spade 2 Senior Member

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    Lots of good information in this thread.

    The overriding factor might be:
    You have a car that is 16 years old.
    It didn't have a LOT of power when new and likely has less now......both from the gas engine and the HV battery.

    You are going to have to push it harder to maintain speed going uphill.
    Accelerating to a bit OVER your desired speed before you start up the hill might help.

    And I don't remember the use of cruise control coming into the discussion.
    If you haven't tried that, you should. It might be better........or it might not.
     
  18. srellim234

    srellim234 Senior Member

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    I've driven all three routes multiple times: I-80, I-70 and I-25/!-40. The southern route (I-25/I-40) is the easiest but the longest way back from the Denver area. The northern route through Wyoming on I-80 is going to be pretty easy on the car too when travelling from east to west if the headwinds aren't too strong. It seems like it is always blowing strongly from west to east out there. I-70 out of Denver is far and away the most scenic but is definitely the toughest on a Prius. The best thing I can suggest is to take it slow climbing the passes and stay to the right, following the lead of the 18-wheelers. On some of those inclines the only thing you gain by flooring it trying to get more power out of the car is to drain the battery quicker. The climb to the tunnel will slow you down but it also comes early in the trip.
     
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  19. privilege

    privilege Active Member

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    fill up with non ethanol fuel ( 87/89/93 doesn't matter) , then try again. oh ya, you can mat the accelerator, it's fine.

    at 10k feet there's a significant power loss for normally aspirated engines (non turbo, non super charged) ... so ya, you may feel like you're standing in it to maintain speed.

    all of this sounds normal so far
     
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  20. ChapmanF

    ChapmanF Senior Member

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    This is well put. Although normal cars are different, there are two kinds of things that do act like a Prius: airplanes and boats. Their engines are not driving wheels that are locked to the pavement, so their engine sounds are not ground-speed dependent. Instead, the engine sound just straight-out tells you how much power is being produced. A Prius is the same way.

    In an airplane's takeoff run, you don't hear the engines winding higher and higher all the way down the runway; you just hear them wind up to high power right at the start of the run, and just sound about the same throughout the run, while the plane picks up speed.

    A Prius isn't in any kind of trouble when it sounds the same way.
     
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