Tacoma running poorly, won't accelerate at all/tachometer "bounces" - what could be problem?

I noticed that my truck isn't running as well as it used to. There are no glaring issues, starts and idles just fine. No check engine lights or codes. When I accelerate, it trudges upwards slowly. If you really try to stomp on it, it is almost as if the tachometer literally bounches slightly as if it doesn't want to get above 2,000 rpms and it never does.

I have looked into cleaning throttle body as a fix but I am not sure what it could be. Fuel injectors?

Air filter is clean, and it is not due for an oil change. I am very frustrated as this is one of those problems that is hard to pin down.

 

Odd that there's no codes or CEL if it's running that poorly, almost sounds like it could be a plugged converter/exhaust.

 

Does it do the same thing in Neutral or Park?

 

No, it only does it when really stepping on it. Now i get it, these trucks are not race cars. However, my 4.0 has some get up usually and I have had this truck since 2013 so I know how it drives well. It won't bounce if you're just steadily increasing speed - it's when you go to pass someone or merge on the interstate that you notice it really struggling.

 

I think that's what is most frustrating to me... it isn't that it is necessarily running poorly. It only does that when you really step on it. That is when the tach starts bouncing. If you just drive extremely conservative and only around town/not on the interstate you wouldnt notice the problem. It idles fine, cruises fine, so it is odd.

 

When you say the tach bounces is it like it's hitting a rev limiter or is more of a random twitch?

 

It starts right at 1,900 rpm... it is almost as if it absolutely does not want to pass 2,000rpm and so it stays right there bouncing while the truck very reluctantly and slowly speeds up.

 

Start with new spark plugs

 

Have you checked your maf sensor? Does it feel like a bog, or just doesn't want to accelerate?

 

You need some kind of scanner to read what's going on. Just because a engine light is not on doesn't mean something is going on somewhere. There could be a pending code(s) not illuminating the check engine light. Fuel trims and Mode6 data is very telling of what's up.

 

You are absolutely right. I tried taking it around the block with OBD scanner plugged up and i'll be honest unfortunately I dont even know what to look for if there was something telling in the data.

 

Totally right. Could be a fuel pump going bad, or fouled fuel line.

The potentially easiest spot would be to look at values below 2k cruising, then try and watch how they change when you accelerate. Also could help to find a friend with a taco and see how his measurements behave under the same conditions.

 

This would be a good thing to check if they have never been done, plugs are due on the 4.0L every 30k.

 

The scanner that you have plugged in should be able to retrieve any DTC'S or pending DTC's

 

This sounds like an exhaust issue, or the ECU is intentionally cutting power.
You think you’d get a CEL for misfire, rich, or lean, TPS - something?

 

I was check fuel pressure based on your description. I think this engine has a fuel rail pressure sensor, your scan tool should be able to show this value.

Its unlikely but if you don't know the last time it was done it wouldn't hurt to clean the throttle body and MAF sensor, also replace the spark plugs.

 

There's no fuel pressure sensor on 2nd gen Tacoma's, fuel pressure has to be checked manually by teeing a gauge inline.

 

Dang I thought there was a sensor, guess I was thinking of the pressure regulator.
One of the part store loaner tool programs may have a manual fuel pressure tester.

 

Fuel rail pressure sensors didn't really become prevalent until manufacturers started using electronic returnless fuel systems and direct injection.
The easiest place to tee in is on the drivers side where the fuel lines from the engine connect to the steel lines on the frame.
I believe the forward most line is the pressure line but I'm not 100% on that.

 

I’ve never checked the fuel pressure and don’t know what line is which.
Toyota says to T in at the #1 fuel pipe. That’s the line that connects to the fuel rail on the drivers side. You might follow that line back to the one @Dm93 posted and try there.
Pressure should be close to 41 psi.

Still be nice to see fuel trims. But you work with what you got