Need brains, diagnosing supercharged 1GR-FE issue

Thanks for all for so much great info!
@ROAD DOG I really hope its not wiring to injectors, what a pain that would be. Could be injectors clogged but its more hassle to get the supercharger off so was hoping to leave that until I had ruled other stuff out.
@Dm93 all the bits are TRD factory done by the book
@MA_TACO that's super useful, sounds like the same issue as you had so vacuum leak is firming as a culprit which I had mostly dismissed because I couldn't find a leak between the throttle and supercharger. I didn't think there were so many vacuum hoses with so much influence over performance.
@12TRDTacoma The truck is an 08 with 200,000 miles. Great tip on where to check fuel pressure. I've never used a smoke machine, I'm going to google it now. Sounds again like vacuum leak is firming which I'd dismissed a bit thinking it wouldn't have this effect

I found this over on a South African forum that seems to suggest that the fuel pump has two stages or levels. Maybe my issue occurs at the top end of the low stage before it kicks up to a higher flow rate.
https://www.hilux4x4.co.za/views/viewtopic.php?t=43324

So from all your input the next step is to figure out this smoke machine thing. I guess you somehow stick it onto the air intake, pressurise it and wait to see where smoke comes out. I can't hear or feel any leaks but that's not a very scientific check given how noisy the engine is when running and how much air the fan pushes around. Spraying brake cleaner didn't do the job but these hose type leaks wouldn't be impacted by that anyway.

Thanks for the input. I'm off to find who has a smoke machine. If nothing looks like its leaking I'll test the fuel pressure and maybe buy a fuel pump.

 

Sorry, been a bit slow on the repairs, but have swapped out the fuel filter today and hasn't made any change to the hesitation. Fuel that ran out of the old one looked pretty clean from both ends. Next two options are fuel pump and smoke test (although all the pipes looks ok). If its neither of those then, uuurgh, injectors.

 

Before you do anything major try pouring a can of Seafoam in your fuel tank at your next fill up. That stuff cleans out your fuel system pretty good. I use it every couple of months on my truck.

 

Ah ok, looks like they have a few, motor treatment, motor treatment pro, motor treatment high mileage, IC5 petrol fuel injector cleaner?

 

Thought maybe I could do what this guy does and clean the injectors without taking them out (and having to remove supercharger) https://www.youtube.com/watch?v=aDvtzg-ThZs

 

How do you test for fuel pressure on a 1GR with a supercharger on top. Is there a bung in the rail you can plug a gauge into? Or do you get some inline thing and put it above the fuel filter? And how do you check it while driving?

 

https://urdusa.com/urd-fuel-rail-tap/

URD Fuel rail tap and add your gauge to that

 

Hi All,
thanks for the input so far. Have just rigged up an Actron fuel pressure gauge above the fuel filter. Not a dead head, have put in a T and run the gauge off that T so I can see it while I drive it. It comes back as just under 30psi at idle, then when the revs rise to 1800-2300 and the engine starts to cough it drops down to around 22psi, then at 2500 rpm its back up to about 28 psi. When I back off it pops up to 38 psi for a few seconds, then settles back to 28 after a few seconds.
This leads me to knock out the injector theory for the stutter. That leaves two possible culprits. First is fuel pump. Not sure why it would have this mid rpm sag unless they run at two speeds and once it jumps up to the high speed setting its enough pressure again. Other possible culprit is fuel pressure regulator. @12TRDTacoma earlier wrote it should be around 41 psi. Unless my new gauge is wrong I'm nowhere near that.

So two questions
1) Is it more likely to be fuel pump or the pressure reg? (reg is cheaper to change first I guess if I can get easy access under the supercharger)
2) could it be something other than pump or reg? Is there something else I'm overlooking like a hose that equalizes pressure or some airflow pressure sensor (i know nothing about supercharged engines)

Thanks in advance

 

At idle




During stutter



Lift throttle, pressure pops up for a few seconds then drops back to 30

 

Here is my answer. There is a simple way to ensure that the FPR is performing as needed. Hook up the FPR instead of to the intake to the capped off nipple at the supercharger. Then take it for a spin with the fuel pressure gauge hooked up. Give it some juice and if the fuel pressure regulator is working, under part or wide open throttle when at boost (all it takes is a few quick depressions) you should see the needle jump up 7-12 psi. That will ensure the diaphragm within the regulator is working properly. This method of test is actually called a boost reference and is actually how I normally run my truck. It sounds like you are otherwise stock and not tuned so I wouldn't run it this way, more so because you are not tuned than anything.

If all checks well with the regulator we move on. That is a good pressure tester that is rarely inaccurate. I also have seen exactly this stutter issue being caused by the pump on various other vehicles before, not this one yet, but that never makes it exclusionary. I would condemn the pump at this point and do a AEM or Aeromotive fuel pump retrofit. Feel free to chime into the supercharger thread that I have created and the guys will give you some pointers on that retrofit if you need it.

 

Got it. Will look at the supercharger anatomy tomorrow.
Found a manual which says this (I've got a Techstream on the laptop so I might give it a go for learning purposes while I've got the gauge hooked up)

Turn the ignition switch ON.
(k) Turn the intelligent tester ON.
(l) Select the following menu items: DIAGNOSIS /
ENHANCED OBD ll / ACTIVE TEST / FUEL PUMP /
SPD / ON.
(m) Measure the fuel pressure.
Standard:
281 to 287 kPa (2.87 to 2.93 kgf/cm2, 40.8 to
41.7 psi)
• If the fuel pressure is greater than the standard
value, replace the fuel pump.
• If the fuel pressure is less than the standard
value, check the connection between the fuel
hose and fuel pump.
(n) Select the following menu items: DIAGNOSIS /
ENHANCED OBD ll / ACTIVE TEST / PRIMARY /
FUEL PUMP / SPD / OFF.
(o) Check that the fuel pressure does not change for 5
minutes.
Standard:
147 kPa (1.5 kgf/cm2, 21 psi)
If the result is not as specified, check the fuel pump
and fuel injector.


I'm not sure what SPD is but for over pressure it says replace fuel pump which seems a bit counter-intuitive.


Add on > Did the test in Techstream, fuel pressure went up to from 28 psi to 34 psi (not 41 psi). Could hear the pump working harder when that setting is switched on.

 

What year is your truck?

 

08 200000 miles he stated before

 

Didn't see anything, but any validation of what tune is on the ECU? Any consideration given to torque management vs yaw/pitch when timing is being pulled? I know there was mention of climbing, but anything off camber, even the slightest. Any ability for someone with techstream to view sensors while you drive also would help.

 

Factory ECU and tune from factory. Happy to monitor sensors, what would I be looking for? A while back I thought it might have been something faulty in the transmission limiting torque but that doesn't explain why it takes off like a rocket over 2500 rpm. Plus it coughs/judders, its not like a smooth torque limiting feel.

 

Ok, so TRD Tune pig rich. I have a few mods done to my trans (rev tek shift kit and HPT shift mods). However, I do get serious hesitation when in overdrive unless I manually pull down into 4th. There are significant different when I am on an on-ramp and leaned over where the engine will pull timing to prevent seemingly rollover in condition with the ABS/TCU. I can explain all of the interface, but not sure the same situation applies in your example as well. Finally, I do believe the fuel rail solenoids may help with some of this lag that we are currently waiting on with R&D finalization from Red Bullet (IIRC). @12TRDTacoma can explain more as he has seen the benefits. All electronic gremlins aside, magnets lose there properties over heat cycles, rubber dry rots over time and this affects our setups that are sensitive to feeding the proper amounts of fuel.

 

Missed that, thank you.

Edit*** Just realized that I had already responded. Lol

 

Upgrade the fuel pump. That's where my money is.

I second this^^^

 

The lag will still be there even with new VVT solenoids, that is a quality inherent to fly by wire issue that you cannot tune out unfortunately, but a stutter or stumble at take off is different from a no response situation, which is where the solenoids can fail and show their symptoms (and new ones can fix those issues).

With saying that pulling timing does not pull fuel pressure. The pressure should always remain the same and if boost referenced, variable based on input PSI.

To answer you question of SPD on the techstream OP, the fuel pump has variable speeds, low and high pressure. It's not just a one speed setup like your traditional GM and pressure begins to occur at cranking, not at KOEO (like a traditional GM yet again).

Your "takes off like a rocket at 2500 RPM but has no balls below that" complaint is the staple issue that is indicative to that of a failing fuel pump. Do your due diligence and rule out other things, but when I see pressures like that which are varying wildly I typically go right for the throat and every time I had done so it wound up fixing the issue.

 

Just spoke to the mechanic who has dropped the new pump in and he says its now revving across the range. Even though it was a easy place to start swapping bits I still don't get the behaviour unless there is a multi stage speed control. Lets say that the old pump is 30% lower than a new one in volume per minute. The old pump would get to the top of the low flow stage at 2300 rpm and it would struggle because its 30% down. Then the ECU tells it 'ok we're at 2400rpm now, kick up to the faster speed' which is also 30% down, but its 30% down on the higher flow rate. I haven't kept it flat all the way to the redline (because this is a lean situation) so maybe it would sag at the top revs as well.
So the only explanation I can see for the behaviour is the pump control is multi stage which I didn't think was the case, pumps are just generally on or off and the pressure regulator would just return the excess that isn't needed.
Will pick the car up in a bit and see for myself. Your thoughts?