Low Power Bad MPG - Need more ideas

[cashmoney]

I know I'm bugging y'all with all of my questions but I'm OCD about my vehicles and it bothers me when they don't run right. Short back story, my truck won't maintain 80mph or even really 70mph (legal limits in parts of Texas) without down shifting even on flat ground and is getting 10mpg. 70 it struggles but 80 it flat just won't do it and is downshifting every 60-90secs. There is definitely a dead spot between 2000-2500 that the engine just flat doesn't want to accelerate and I have to nearly floor it to get it over that and once it's above that range it seems to have normal power. Below that range it's very responsive but in that range it's a pig. Here is what I've replaced so far:

Plugs
Wires
PCV
Fuel Filter
Air Filter
Cleaned TB
Cleaned IAC
Cleaned MAF
Compression Check (150, 145, 155, 155, 155, 145)
Timing Belt (last year)
Tightened throttle cable//cruise cable//trans cable
Confirmed TB is opening 100%
Verified speedo and mileage readings with GPS

Here is my next round of things to replace/change/check:
Seafoam intake and gas tank
All fluids
Deckplate Mod (again, I like to modify)
ISR Mod
TPS
O2 Sensors
Cats//exhaust (I like modified anyways)
ECT Sensor
Fuel pressure
Leak down

Truck is stock with the exception of the 265/75's. I haven't put the lift on yet but it is sitting in my garage. Is there ANYTHING else left that I can//need to do to get the power and MPG up? There are no check engine lights, rough running, hard starting, or smoking. I refuse to believe that a stock 4runner can't maintain speed on flat ground.

 

[jeremyc74]

What you're describing could very well be a fuel pressure issue. I had something similar with the 22RE in my RV and it turned out to be a pinched supply line.

In that case the fuel pressure was fine at idle, but fell off as the demand picked up and caused the A/F ratio to go out of whack.

So the obvious things are the fuel pump, filter and regulator, but I wouldn't just start swapping parts (trust me...I'm out many hundreds of dollars on that RV issue). The fuel pressure regulator has a vacuum bias that causes it to increase as the throttle opens, so it could very well be a vacuum issue too.

I'd slap a fuel pressure gauge on it that you can see from inside, and observe it while you're driving around. It's also possible you have a leak in the intake tract somewhere between the MAF and the head. That will screw things up too.

 

[cashmoney]

It's also possible you have a leak in the intake tract somewhere between the MAF and the head. That will screw things up too.

That's one of the reasons I'm doing the ISR. There is silicone on the intake duct in multiple places that looks//is cracked.

And from what I'm reading, slapping a fuel pressure gauge on isn't as simple as it should be. Gonna have to do some customization to make it work.

 

[gamefreakgc]

Check for vacuum leaks. Most common cause for loss of power and poor MPG's. Sometimes it throws a P0171 code, sometimes not.

 

[Rock_Rat]

Here is my next round of things to replace/change/check:
TPS

No codes? How does it run parked in the driveway without a load on it? Run it with yourself inside the vehicle and outside the vehicle manually operating the throttle cable? Are you getting a good response all the way through the RPMs? Any lag? You may want to check the resistance in your Throttle Control Motor, TPS and pedal.

Check all the obvious stuff first. All wires, connectors, vacuum hoses etc. Your list of things to do aside from fuel pressure and TPS have nothing to do with your problem. The deck plate and ISR mods are pretty much worthless mods IMHO. I've done both with nothing more than an increase in noise and minor pedal response. O2 sensors only monitor, they don't control anything.

Do the easy stuff first before you start throwing big money at it.

EDIT: Just noticed [MENTION=115347]gamefreakgc[/MENTION] replied and has done the deckplate mod with a disclaimer in the tag line about HP gain. I don't dispute the facts and yes it's worth it for the price you pay but hardly noticeable. Personally, I was hoping for more gain with the increase in the noise. It's still tolerable.

 

[Hesk11dog]

second on the fuel pressure/supply issue. Also check all vacuum lines for holes and cracks. If you can get your hands on a laser temp reader, check the intake and exit for the cat. It could be plugged and overheating without throwing a code. Double check that your plugs are wired correctly and that they are torqued to spec.

 

[gamefreakgc]

Yeah it was very cheap and easy so why not? I am supercharged so I need more airflow than a stock rig anyway. The ISR mod though had no proven power gains. Even using Airaid or K&N intakes showed no increase in HP over the stock one from dyno's that I've seen, only more noise. I've done custom cold air intakes on other vehicles, the gains are minimal if at all and my 4Runner is noisy enough as it is.

I may end up switching my filter from the Toyota filters I've got in there now since I don't offroad a ton and when I do, it's usually on rock surfaces with little dust/mud.

 

[cashmoney]

I'm doing those for my own personal amusement. I'm a power junky and if I can potentially get half a horsepower I'm excited HAHA.

As I sit here at my desk looking through vacuum line diagrams a thought has occurred to me. I know I have a vacuum hose going in to my air box and I have a big one right in front of the throttle body, but I'm almost 100% positive I don't have the one that gets rerouted when you do the ISR mod.

 

[cashmoney]

No codes? How does it run parked in the driveway without a load on it? Run it with yourself inside the vehicle and outside the vehicle manually operating the throttle cable? Are you getting a good response all the way through the RPMs? Any lag? You may want to check the resistance in your Throttle Control Motor, TPS and pedal.

Check all the obvious stuff first. All wires, connectors, vacuum hoses etc. Your list of things to do aside from fuel pressure and TPS have nothing to do with your problem. The deck plate and ISR mods are pretty much worthless mods IMHO. I've done both with nothing more than an increase in noise and minor pedal response. O2 sensors only monitor, they don't control anything.

Do the easy stuff first before you start throwing big money at it.

EDIT: Just noticed [MENTION=115347]gamefreakgc[/MENTION] replied and has done the deckplate mod with a disclaimer in the tag line about HP gain. I don't dispute the facts and yes it's worth it for the price you pay but hardly noticeable. Personally, I was hoping for more gain with the increase in the noise. It's still tolerable.

Runs great sitting in the driveway with no load. Was playing with that last night as a matter of fact.

 

[gamefreakgc]

Lots don't, there are only certain years that used the air cleaner hose with multiple vacuum hoses.

 

[cashmoney]

Well dang it. There goes that thought.

 

[gamefreakgc]

Well dang it. There goes that thought.

If you have a can of carb cleaner or MAF cleaner though, it makes checking for leaks real easy:

<iframe width="560" height="315" src="https://www.youtube.com/embed/9CPqbaSgcok" frameborder="0" allowfullscreen></iframe>

 

[cashmoney]

Yup. That's always a fun way to check for leaks and degrease your engine at the same time.

 

[warriorwagner]

If you have a can of carb cleaner or MAF cleaner though, it makes checking for leaks real easy:

<iframe width="560" height="315" src="https://www.youtube.com/embed/9CPqbaSgcok" frameborder="0" allowfullscreen></iframe>

That's a great way to check for leaks, I would have never thought of that.

 

[gamefreakgc]

It's saved my bacon lots of times. The predecessor to our 4Runners, the 2nd Gen had more vacuum hoses than one could count. If one worked on the engine and had a leak after buttoning it back up it was near impossible to find the leak without using this method.

Just make sure your engine is cold ok? Or have a fire extinguisher just in case.

 

[cashmoney]

Any other ideas I can try? Going to start on this in about an hour.

I read a few places that unplugging the TPS is a good way to test if it's functioning or not. Unplugged mine and the transmission was not happy with me. Plugged it back in and this time the idle dropped and came back up. Unplugged it and it dropped and came up. Plugged it back in and it dropped and then came up to about a 1000 for a couple of seconds and then settled back to normal. So I'm guessing it's fine although for $50 I may just go ahead and swap it out anyways.

 

[Supermoney]

Hey cashmoney its me your brother supermoney.

 

[stir_fry_boy]

Any other ideas I can try? Going to start on this in about an hour.

I read a few places that unplugging the TPS is a good way to test if it's functioning or not. Unplugged mine and the transmission was not happy with me. Plugged it back in and this time the idle dropped and came back up. Unplugged it and it dropped and came up. Plugged it back in and it dropped and then came up to about a 1000 for a couple of seconds and then settled back to normal. So I'm guessing it's fine although for $50 I may just go ahead and swap it out anyways.

Sounds like it's working. I wouldn't change it. If you must, only use dealer quality part (Denso) and nothing else. It won't be happy with any other brand.

 

[cashmoney]

Lots don't, there are only certain years that used the air cleaner hose with multiple vacuum hoses.

Well sure enough mine did and it was unplugged. Got seafoam soaking in it right now so won't know until tomorrow if it made a difference. This hose was going back to what looked like a fuel pressure regulator on the back of the engine.

Sprayed every vacuum hose I could find with carb cleaner and no change in rpm.

 

[gamefreakgc]

Well sure enough mine did and it was unplugged. Got seafoam soaking in it right now so won't know until tomorrow if it made a difference. This hose was going back to what looked like a fuel pressure regulator on the back of the engine.

Sprayed every vacuum hose I could find with carb cleaner and no change in rpm.

Almost completely sure that will fix your issue! Hooray for the easy fix.

Seafoam soaking though? Never done that one, seafoam directions say only 5-10 min, but to each his own!