5VZ-FE Cutting power after 50% throttle

Hi all,
I have a 2001 Tacoma, V6, 5 speed manual, 4WD. Also added Magnusson supercharger, URD piggyback tuner with 7th injector, upgraded fuel pump and all small mods recommended with the upgrades I did. Truck ran great for 30k+ miles staying on top of maintenance.
The other day truck started cutting power but only if you step on it. Can still drive it fine as long as you don't step on it. Will rev to 5k+ if you go easy. I have fuel pressure gauge hooked up to one of the fuel rails. According to the gauge fuel pressure isn't an issue. When the power loss happens the wideband O2 gauge goes full lean. Kind of expected but don't know what's causing the power cuts.
There is no CEL and running scans with OBDII code reader says everything is normal. Just looking for a place to start to diagnose the problem.

 

Check,
1) fuel filter
2) depending on miles injectors might need rebuilt because each has a fuel filter,
3) bad MAF sensor, has to be OEM, lots of fake ones in fake boxes out there.
Or needs cleaning,
4) 02 sensor could be bad.
5) Any vacuum leak will cause issues even a small one, check every hose.
6) any exhaust leak infront of the 02 sensor
7) the fuel pressure gauge you have to monitor on load, at idle tells u nothing, a bad fuel pump can fail at higher rpms on load and look good at idle.
8) fuel pressure regulator
9) bad coil or coils, they will not throw a code.
10) did u put in 2 step cooler plugs?
11) knock sensors

can be any of these above,
Start with the easier 1st

 

This happened to me on my 3RZ. First time turned out to be the aft Cat filter, it had turned sideways and caused exhaust discharge issues. Fried my EGR modulator and valve. Second time, my Cat clogged due to the truck running like shit, and I had to hollow out the cat. Had to change my EGR modulator again.

Check your cats somehow. Keep an eye on that EGR modulator. You'll hear a loud hissing sound once its completely melted away.

 

Don't listen to me, but it sounds like a vacuum leak.

 

MAF is OEM and was cleaned pretty recently, I replaced both pre and post cat O2 sensors in last 6 months, as for fuel pressure gauge I was monitoring under load, at around 40psi at idle and jumps to around 50 under load, no drop during the power cuts. When I did the supercharger I did upgraded spark plugs to whatever URD recommended at the time as well as new coil packs. I replaced knock sensor a year or 2 ago so doubt thats it. I'm thinking its injectors or possible vacuum leak. Thanks for the suggestions

 

2 new cats last month. Front cat went bad and threw CEL. Replaced O2 sensors first hoping that was it but ended up being bad cat. So i got brand new cats and O2 sensors

 

You can do a smoke test for the vacuum, sometimes the master brake booster can be the issue

 

truck has 129k miles. how many miles recommended for injector rebuilds?

 

Typically around 150k the fuel filters start getting a little plugged up but that should not be cutting the engine usually,
I’m guessing if there’s only 130kmthats not the problem

 

Had this exact same issue on another vehicle also with a roots type supercharger. When you go WOT the car falls flat on it's face and stumbles. But if I gradually apply the gas it will climb the rev range just fine. Basically, you just can't go into boost or it will stumble. Turns out that the bypass valve inlet was clogged. I'm not sure about your BPV but mine had a small brass fitting with a small hole in it and the function of it is to make the transition to WOT smoother. All of my problem went away after removing it but it would have done the same if I just cleaned it out.

 

What caused the cats to go bad? Were you running too rich with the fuel system upgrades you did?

 

I posted about this many years ago on another forum. I provided the link below. Check out post #5. I hope this is your issue as well as I was pulling my hair out over it. You mentioned you were going lean but I was going rich. Are you verifying with a wideband? You can test it by removing the hose from the intake manifold to the BPV and cap off the hose itself and see if the problem persists. Worth a shot since it shouldn't be that hard on these trucks but I've never had a SC on these before.

https://www.lotustalk.com/threads/bwr-supercharger-koldfire-tune-issue.246505/#post-3361625

 

Could be the vacuum to the actuator on the supercharger or the actuator it’s self, I’ve had mine go south before and bought a new one from LCE

 

This sounds exactly like my problem. I was just out of town for a week and came home and filled up the truck with gas. On the drive home from gas station I gave it WOT 1-3 pull just to see and there was no problem. Gonna check out that BPV though because I find it very weird it just fixed itself

 

Not 100% sure but I bought the truck at like 85k miles completely stock. Was a beater farm truck before I bought it. Around 110k miles I got CEL with P0420 code ( I believe that was the code) something to do with catalyst efficiency. Was hoping it was just a bad sensor so replaced both pre and post cat O2 sensors. That didnt fix it so finally just did the cats. That solved the problem. Guy who did cats for me said front cat had some cracks and pieces rattling around inside. Im guessing its life on the farm may have had something to do with that. Still not 100% sure though