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Poor performance uphill


jp4036
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Hi everyone - First time posting, but thanks to everyone on this forum. Reading through existing threads has been immensely helpful in diagnosing other issues!

 

I wanted to see if anyone had any ideas about an issue I am having with my 2000 LE Pathfinder (VG3.3). It's relatively new to me, but has about 200k miles on it. 

 

The issue is this: when going uphill, the truck seems to really struggle and have low power. It feels like no matter how hard I press the gas, I can't get the engine above 2-2.5k rpm in that particular gear (I think it's 4th, but it might be 3rd). This keeps me stuck 10mph below traffic -- depending on the grade, this means I'm stuck around 30 mph or, for steeper hills, 10-20 mph. 

 

However, when I lean into the gas pedal even harder, it downshifts and the rpms jump from the 2-2.5 all the way to to 3.5-4k. Then I get acceleration again, but I get nervous revving the engine that high for sustained periods of time and with a sudden and aggressive shift like that. 

 

It's also been worth noting that if I sustain the uphill like this, the temperature gauge might start to creep up, forcing me to pull over and wait for things to cool down. (I'm not completely sure whether this is related or not, because it's been super hot lately - this is happening with 100 degree ambient temperatures).

 

Granted, I'm talking about mountain driving in Colorado - so there's altitude on top of the grade and heat. But it still feels like something is wrong and the cars driving behind me are pretty frustrated too. 

 

It accelerates fine on flatter ground, and I don't have a problem getting up to highway speeds during normal driving. I've replaced the spark plugs and wires, fuel filter, air filter, cleaned the MAF and throttle body. I've also replaced all the fluids and the transmission filter. Just had the timing belt, water pump, and knock sensor replaced. 

 

I do have an EVAP leak which I am planning on fixing, but I doubt that's the issue. I took it to a mechanic recently, who could not find any vacuum leaks. They also tested the fuel pressure and said it was in spec. Not getting any engine codes other than the evap leak. The mechanic took it up a small hill nearby, but it wasn't sustained enough to recreate the issue. They said it felt like it accelerated fine for a 3.3l engine with 200k miles on it.

 

Also worth noting it's got a 2in lift, and heavy 32in tires with steel rims. Running manual hubs unlocked. 

 

Any ideas? Is this normal for the vg33, or are there other ideas on how to tackle this issue?

 

Thanks again!

 

 

 

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I'll preface this by saying that I have a VQ35 Pathfinder and don't have direct experience with a VG Pathy, however:

 

1. It's my understanding that the VG's are pretty under-powered. For example I was following a friend and former 3.3 Pathy owner who still frequents NPORA forums ( @zakzackzachary ) up a highway grade. He radioed me and asked how my 3.5 was doing out of curiosity - I never went beyond 1/4 throttle and stayed in 3rd gear the whole way up. He said that his 3.3 would have been screaming at full throttle by the top of that grade just to keep up with traffic (correct me if I'm wrong Zack). I would expect this to be even worse at Colorado elevations. 

 

2. Your 3.3 is a stout engine - I wouldn't be super concerned about running at 3.5-4k RPM for a period - it can handle it.

 

Because of this I'd be more concerned with the over heating. Consider checking the condition of the radiator, doing a coolant flush, check for coolant leaks, check condition of the radiator cap seal etc.

 

I'm open to being corrected by others as well...

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:welcome:

 

Sounds a lot like how my '93 drives! I think the trouble with mine is as much the engine being gutless as the transmission doing dumb things. Shifts up too soon, doesn't want to shift down again, then acts all surprised that my foot's on the floor and revs the tits off the engine trying to catch up. Turning off the overdrive on hills helps a lot, both because it can't grab overdrive while climbing and because I've got some engine braking on the way back down. It changes the behavior of the torque converter, too. Mine's also got an E-AT switch, which bumps up all the shift points. I leave that one on all the time. I don't think the R50 got that switch, though.

I've got a VG33 with VG30 cams in it waiting to go in my '93. That's the usual strategy for warming these up. Past that, you're looking at forced induction and/or machine work. Sounds like you've got most of the tune-up stuff dealt with. Check your ignition timing (should be 15° +/- 2 at warm idle) and check the intake boot between the MAF and the TB for damage. While you're under the hood, check the data plate in the engine bay, see if you've got HG43 or HG46 diffs. Auto usually got HG46, but if you've got HG43, you can swap in the 4.6 diffs and get a little torque back. 

I hear you on holding up traffic. I got passed by a Winnebago in my '95. I wasn't even trying to let him by.

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Thanks so much for your thoughts!

 

I did have a small coolant leak in the thermo element of the throttle body. That seems to be a relatively common issue. Not sure if that would be a big enough deal to cause overheating under heavy load -- I wasn't losing much coolant -- but perhaps it impacted the pressure in the system. 

 

I've replaced the oring and sealed everything with RTV. (Great how-to here: https://www.clubxterra.org/threads/thermo-element-idle-sensor-rebuild.38432/). Would have replaced the whole thermo element, but that part is shockingly expensive.

 

Hopefully that will solve the coolant issue. The fluid itself is still very new, as is the water pump and thermostat.

 

 

Regarding the low power frustration -- I'm glad to hear that this is probably just a result of the engine being underpowered and the transmission being frustrating. Next time I'll try turning off overdrive and just being willing to run at a higher rpm for more power. Maybe that will also help the fan run a bit faster, and higher speed will help airflow over the radiator as well.

 

I'll post an update and let y'all know how it goes!

 

 

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Did you bleed the cooling system after fixing the leak? There's a bolt on the intake manifold, should be marked "do not open when hot." Remove the bolt (with the engine cold, obviously), gently squeeze the upper rad hose until coolant rises up to the threads, then hold it there while you put the bolt back in. Check the rad, top it off if needed. Might help. That said, the temp creeping up when you're pushing it hard on a 100° day does not surprise me. The one time my '95 tried to overheat was under similar conditions.

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Thanks again everyone. With the coolant and evap leaks fixed, overheating seems to be less of a dramatic problem. Pushing it hard on a super hot day still made the gauge want to tick up slightly, but overall it definitely feels like it can handle these uphills much better. Thanks for the tip on an easy bleeding too - that'll help as well.

 

Turning overdrive off didn't fix the aggressive downshifting - I guess it wasn't making it all the way up to that gear. But letting the transmission do what it wants to do seems to be pretty manageable. When it downshifts, it will hit 3.5k rpm and accelerate for about 5 or 10 seconds to get the speed back up, before shifting back up again. 

 

Without having to worry about overheating, this actually feels fine and is much more fun to drive.

 

Thanks for the help!

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On 7/20/2022 at 6:12 PM, The_Oregonian said:

1. It's my understanding that the VG's are pretty under-powered. For example I was following a friend and former 3.3 Pathy owner who still frequents NPORA forums ( @zakzackzachary ) up a highway grade. He radioed me and asked how my 3.5 was doing out of curiosity - I never went beyond 1/4 throttle and stayed in 3rd gear the whole way up. He said that his 3.3 would have been screaming at full throttle by the top of that grade just to keep up with traffic (correct me if I'm wrong Zack). I would expect this to be even worse at Colorado elevations. 

 

Yeah the 3.3 I had was a solid engine, but boy she screamed when having to go at high speeds haha. The 3.5 has an extra like 100hp which shines there.

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  • 1 month later...

Would the throttle position sensor have anything to do with acceleration and the way the trans acts? Curious because I was told once by a mechanic that throttle issues and trans shifts have a lot to do if the TP sensor is set correctly.


Sent from my iPhone 8 Plus using Tapatalk

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