Lack of Power – V6

[So Many Roads]

I have a ’99 5 speed, 6cyl, bought last year. 130k miles. It’s always been pretty slow, especially in the mountains. Passing on the highway is difficult. Last week, going East on 1-70 I had a hard time holding 50 mph going up Vail Pass and towards the Eisenhower Tunnel. Another 3rd gen passed me like I was standing still. Any thoughts on why the engine is putting out so little power and what I might do to fix?

All maintenance is up to date. Timing belt replaced at 90K. In the last six months I’ve done denso plugs and wires, fuel filter, air filter, all fluids. Checked MAF sensor; looked clean at the time and I did not clean it. Truck passed emissions when purchased, does not put out any smoke, no CEL’s while I’ve owned it. I get about 21 mpg on the hwy, 19 around town.

I am going to run some redline fuel injector cleaner & clean the MAF sensor. Other than that, my thoughts are the fuel pump or the fuel injectors. Any suggestions on what else I could look at? Appreciate the input.

 

[Atreyus]

I'm having the same problem, I'm going to get my fuel pump checked out and hopefully it's just that, I had a misfire a few days ago and found out it was a faulty injector.

 

[Stick Figure]

have you done a compression test or leak down test? I know there are no signs of being down on compression but this will make sure.

Other question:

What upgrades have you done?

BIG HEAVY tires will kill your acceleration.

you already drive a brick, did you lift it? that won't help matters.

More load on the charging system will hurt things a little too

so will extra weight

Beyond that .. how is your transmission?

 

[So Many Roads]

have you done a compression test or leak down test? I know there are no signs of being down on compression but this will make sure.

Other question:

What upgrades have you done?

BIG HEAVY tires will kill your acceleration.

you already drive a brick, did you lift it? that won't help matters.

More load on the charging system will hurt things a little too

so will extra weight

Beyond that .. how is your transmission?

No, I have not done a compression test. Tires are stock 31", no lift yet. No mods that draw any power. Clutch does not slip, so I'd guess transmission is ok.

 

[Dan.3]

is your exhaust clogged up?

 

[Stick Figure]

exhaust, particularly damaged cats is a good idea too.

With the manual trans yeah if the clutch isn't slipping you are good I was thinking more auto trans (even though you said 5 speed) Only other suggestion would be to check your fuel trims and see if they are close to zero or if they are way out like the ECU is trying to compensate for something or the o2 sensor is on its way out.

Maybe the other 3rd Gen was supercharged! lol ... Although I think I've pulled up that same stretch faster than 50mph with a small trailer. Keep in mind I'm also not afraid to push my truck pretty damn hard to maintain the speed I want.

 

[So Many Roads]

Thanks Stick Figure. I'll check the fuel trims and exhaust system. If anyone else had similar problems let's hear what you figured out.

 

[steezemcqueen]

My truck used to lack power. I added a supercharger and that pretty much fixed it :biggrin2:

 

[02SE]

I recall a post on here years ago from someone that was complaining of a lack of power on steep mountain grades. They also had a manual trans.

As it turned out, this person didn't understand that you could shift down to 4th, 3rd, 2nd, or even 1st, as long as you aren't running the engine into the rev-limiter, if you wanted to maintain a certain speed up the grade.

So I assume you're not like that poster, and downshift as needed to maintain the desired speed.

That said, Vail Pass, and heading up to the Eisenhower Tunnel are steep grades, at high altitude. Lots of vehicles struggle up those roads.

Perhaps the 3rd gen that passed you had forced induction.

 

[So Many Roads]

you could shift down to 4th, 3rd, 2nd, or even 1st, as long as you aren't running the engine into the rev-limiter.

Really? No, I got that.

This truck is way underpowered, some tests should be helpful. It has to be the fuel mix, exhaust, or heads. Hopefully not the heads. I'll figure it out. Thanks for the input.

 

[kball]

Sounds like you're getting pretty good mileage. Maybe check your throttle linkage and make sure you're getting full throttle. Maybe something is bent..?

 

[1985taylor1925]

Since this is part of the discussion anyways, how do you know if you have a clogged cat? What kind of tests will diagnose that?

 

[PitbullRescuer]

Sounds like you're getting pretty good mileage. Maybe check your throttle linkage and make sure you're getting full throttle. Maybe something is bent..?

This! Might be a long shot but it's not uncommon. Open the hood and see how much slack is in the throttle cable. My '97 looked like a swing. Tightened the cable up and it was like a new truck.

 

[Stick Figure]

Since this is part of the discussion anyways, how do you know if you have a clogged cat? What kind of tests will diagnose that?

Best way is with expensive pressure sensors tapped in before and after. Other methods are infrared thermometer to check if its getting overly hot, remove for visual inspection or TEMPORARILY replace it with a "test pipe".

 

[So Many Roads]

Closing out another rookie post with what I found...

Many thanks to kball and PitbullRescuer for pointing me in the direction of the throttle cable. The accelerator cable was so loose it looked like a big smiley face, which kept the throttle from opening all the way. Tightened that up and wow! By far the single best 30 second repair I could imagine.

Thanks!

 

[kball]

Glad you got it fixed. Now don't be surprised if your city mileage goes down a bit. I thought 19 sounded too good. You were forced into granny mode by the loose cable!

 

[PitbullRescuer]

That's awesome, glad it worked out.

As far as mileage, I must say I'm uber impressed with my 5 speed. I filled it up for the first time last week, got 345 miles out of the tank.

I am surprised though, I did try to run it low, both fill up so far have been about 16.5 gallons before the pump stopped. Do the 5 speeds have a bigger tank than the automatics do?

 

[02SE]

All 3rd gen 4Runners have an 18.5 gallon tank. My V6 5-speed gets noticeably better MPG, than my Sister's V6 auto. Both are 4wd, stock ride height, with the same size, style, and load range of tire.

We've noticed that several times over the years, when we were both driving the same route, following each other to family outings.

 

[PitbullRescuer]

I thought the stock tank was 16 gallons?

 

[02SE]

Nope, all are 18.5 gallons. But as has been discussed many times over the years, using all of that can be difficult for several reasons. Such as being on a road that isn't perfectly level, gas sloshing around in the tank when it's nearly empty, so that the pump can't pick it up consistently, etc.

The pumps are cooled by gasoline too, so running the 'Runner really low on gas before filling up every time, theoretically could shorten the life of the pump.