Sluggish 4.7 VVT-I

[4OYOTER]

I have owned my 4th gen for about 6 months now. At first I was really impressed with the acceleration and throttle response. Well recently I have noticed she seems to be no where as peppy as she used to be. I have 116K. All obvious tune ups have been done (new spark plugs, air filter, and ran fuel system cleaner.) I have tried premium gas, but no big difference. The only thing I know I'm past due for is my timing belt job, but I don't see how that could effect performance. I don't have any CEL. Maybe I just got used to her? But I've also driven a few 4.7 tundras and a GX470 lately that seemed like they had a whole different engine!

Any ideas? Gas mileage has stayed consistent at around 13mpg mostly city driving.

 

[4OYOTER]

Forgot to mention my tires are p265/70r17 and I'm bone stock with no extra weight. Only other thing of mention is that my transmission was replaced with a used one by my extended warranty company shortly after getting my 4th gen, to solve my prior "rumble strip" issue.

 

[MACT4R]

Have you done rear differential fluid replaced? Just a thought because mine had the same issue of no pep but soon as I chaned rear diff oil, got the pep back. My oil was dark and thick. Just a thought.

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[V8Man]

Forgot to mention my tires are p265/70r17 and I'm bone stock with no extra weight. Only other thing of mention is that my transmission was replaced with a used one by my extended warranty company shortly after getting my 4th gen, to solve my prior "rumble strip" issue.

Check to see if you have the calipers stuck on your front brakes.

 

[MrRoo]

Have you done rear differential fluid replaced? Just a thought because mine had the same issue of no pep but soon as I chaned rear diff oil, got the pep back. My oil was dark and thick. Just a thought.

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Umm, hmmm...........

 

[m85476585]

Could the throttle body be sticky? Cleaner in the fuel tank won't fix that.

Could the transmission fluid level be wrong? The symptoms are usually different (not going into gear right away), but maybe that could do it.

Oil that's too thick could be a problem while the engine is cold. You should use 5W30, and synthetic is ideal if you make a lot of short trips.

I think mine has different levels of responsiveness depending on how much it's warmed up, but I haven't tested enough to know for sure.

 

[MACT4R]

Umm, hmmm...........

Yes, a little hmmm. After installing the spartan locker and new gear oil, I was able to have the get up and go. This is after changing engine oil, checking tranny and other things. Just a thought to throw out there.

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[4OYOTER]

Thanks for the replies. I have not checked the diff fluids yet, will do that ASAP. I cleaned my throttle body when I did my spark plugs, so I can rule that out. I just switched to Mobil 1 5w-30 high mileage, no difference. I had pondered the sticky calipers idea, I will look more into it now. I haven't noticed any pulling, but I suppose if they were both sticky I wouldn't have a pull? I did notice my front rotors have multiple deep grooves all around the rotors, not sure what that's about.

I had also thought about the tranny fluid being low, but without other symptoms I'm hesitant to take it back to the dealer who installed the new transmission to check the fluid. I might check the fluid myself if I comes to that point.

 

[Morphyne]

PCV valve

 

[Bob22222]

Thanks for the replies. I have not checked the diff fluids yet, will do that ASAP. I cleaned my throttle body when I did my spark plugs, so I can rule that out. I just switched to Mobil 1 5w-30 high hmileage, no difference. I had pondered the sticky calipers idea, I will look more into it now. I haven't noticed any pulling, but I suppose if they were both sticky I wouldn't have a pull? I did notice my front rotors have multiple deep grooves all around the rotors, not sure what that's about.

I had also thought about the tranny fluid being low, but without other symptoms I'm hesitant to take it back to the dealer who installed the new transmission to check the fluid. I might check the fluid myself if I comes to that point.

Could be a case of you fixed it till it broke?
If your brakes are dragging they will get hot without moderate or heavy peddle application, meaning like just going down the road without braking. Even cost to a stop or slow gently to pull over to check temps. If they are really dragging quite a bit you should smell them.
Have you checked for clogged cats? How did you clean your TB? Have you checked for pinched or restricted exhaust? Something stuck/partly blocking in the cold air intake's intake port?
I really don't think it's your transmission fluid, diff fluid, or other fluid. There is a remote possiable to your timing belt (v8 right?) could have jumped a tooth, but that's really remote and highly unlikely. Have you considered professional help?

 

[rooost]

Just wait for a cold front...then she can breath again and scream like hell !!!!!

 

[4OYOTER]

Just wait for a cold front...then she can breath again and scream like hell !!!!!

I was actually about to post about the temperature finally dropping below 70 degrees here for the first time in months.. I immediately noticed improved acceleration on my drive home last night...

 

[4OYOTER]

Could be a case of you fixed it till it broke?
If your brakes are dragging they will get hot without moderate or heavy peddle application, meaning like just going down the road without braking. Even cost to a stop or slow gently to pull over to check temps. If they are really dragging quite a bit you should smell them.
Have you checked for clogged cats? How did you clean your TB? Have you checked for pinched or restricted exhaust? Something stuck/partly blocking in the cold air intake's intake port?
I really don't think it's your transmission fluid, diff fluid, or other fluid. There is a remote possiable to your timing belt (v8 right?) could have jumped a tooth, but that's really remote and highly unlikely. Have you considered professional help?

I haven't checked for clogged cats or exhaust issues. I've assumed something that would result in a CEL. I cleaned my TB my simply spraying TB cleaner and using a tooth brush and rag. I didn't remove the whole TB. I have considered having a professional look at her, but I've not really had great experiences with shops so I usually try to do as much as I'm comfortable with myself.

Any ideas what would cause such a huge difference in performance between an ambient temp of say 67 degrees and 75 degrees? As stated above I noticed she drives MUCH better since we finally saw a glimpse of a season change here. I tried A/C on and off but can't tell a difference

 

[CXS]

A change in responsiveness with an 8° change? I can't believe that myself. In CO these days temps change a lot more than that in a couple hours. Strange if it's actually happening but I've never noticed a performance change regardless of temperature or altitude that's noticeable outside of winter gas changes that we have no control over.

 

[4OYOTER]

A change in responsiveness with an 8° change? I can't believe that myself. In CO these days temps change a lot more than that in a couple hours. Strange if it's actually happening but I've never noticed a performance change regardless of temperature or altitude that's noticeable outside of winter gas changes that we have no control over.

Yeah, I'm quite surprised and confused myself.

 

[duffdog]

o2 sensors? theres 4 and 2 of them are responsible for getting the correct A/F mix. They aren't expensive to replace and definitely have to be replaced on high mileage vehicles because they wear out and stop providing the right values to the ECU.

 

[super.secret]

Sometimes, re-setting the ECU allows it to relearn new maps and in turn hopefully bring up your MPG and over all HP and TQ

 

[Bob22222]

I haven't checked for clogged cats or exhaust issues. I've assumed something that would result in a CEL. I cleaned my TB my simply spraying TB cleaner and using a tooth brush and rag. I didn't remove the whole TB. I have considered having a professional look at her, but I've not really had great experiences with shops so I usually try to do as much as I'm comfortable with myself.

Any ideas what would cause such a huge difference in performance between an ambient temp of say 67 degrees and 75 degrees? As stated above I noticed she drives MUCH better since we finally saw a glimpse of a season change here. I tried A/C on and off but can't tell a difference

Cats can and do clog without setting codes. Think of your engine as a gaint air pump (propelled by a bunch of well time explosions in the combustion chamber) if the air flow is restricted the pump cannot move the needed volume of air through it to achieve desired performance, we all know that right? Clogged cats or restricted intake/exhaust can have the same effect as only applying part throttle and the ecu can read it that way. Speaking of air flow have you checked to make sure you are getting full throttle when the accelerator peddle is fully depressed (by the way you did check for an obstruction under the peddle, right?). As for the 8 degree difference ambient temp thing, that really makes little sense (like the faulty fluid theory) makes little to know sense unless you have a very wierd and equally unlikely condition that a sensor is failing only in that range, but I don't know if 8 degrees is enough significanly change the ambient temps of any modules. It damn sure ain't the change in the volume of oxygen per cubic volume of air consumed. Could it be that you have strong or strong enough winds in your area that may vary by strength and direction. Winds shifts are often accompanied by a dip or rise in temperatures.

 

[GrassFed]

If you have an android phone the Torque Pro app and a bluetooth adapter for your OBDII port can show you if your O2 sensors are operating properly as well as other useful information. A big one that doesn't get talked enough about is fuel trims. If you have the means to go this route it makes troubleshooting a whole lot easier and definitely more fun, at least for me.

Throttle body cleaning is great, but will yield more results on the low end, idle/ throttle response ETC. Once the butterfly starts to open you are relying more on other things. Have you cleaned the MAF?

At any rate, best of luck and don't give up - these V8s with the VVT-i are way too much fun to drive when they are running right. I've never driven an SUV with so much jump and torque off the line before.

 

[rooost]

I was actually about to post about the temperature finally dropping below 70 degrees here for the first time in months.. I immediately noticed improved acceleration on my drive home last night...

Ill find myself with a huge smile when behind the wheel...like all is right in the world, then I remember HELL yea cool air makes driving so much more fun! The best power adder cause its free
.
.Might also be why I despise the mountains!