TRD hesitancy on partial throttle

[bricksnmortar]

Hi All,
have an issue I can't get my head around. Have a TRD 4000 SL supercharged Hilux. On gentle throttle (say first 20%) it responds as it should with gentle acceleration. From there up until flat to the floor it hesitates and won't accelerate. When I floor it, it kicks down a few gears and takes off flat out. No OBD error codes. Cleaned the air intake sensor but no difference.
At first I thought it was one of those electronic accelerator response adjusters but looked under the dash and behind the glove box but can't see anything.
No idea what to try next. Obviously the fuel pump and injectors can deliver enough juice (has fresh fuel) because it goes fine flat out. I can't even work out if its engine or a transmission issue telling the ECU to back off. Car is stock standard except for trailer brake adjuster.
Any thoughts about what to try next would be gratefully accepted!

[241steve]

what codes you getting? if its drinking fuel look for a stretched timing chain
I used to like 1gr-fe until I brought 1.

[bricksnmortar]

No codes. It does drink fuel but I'm guessing that's just a byproduct of having a supercharger.
I'll start with looking for hoses that are leaking and PCV as suggested by Gulfstream8

[bricksnmortar]

So I've hooked up my OBD phone code reader to the car and this is what I think I now know
- Hesitancy between 1900 – 2400 rpm (consistent, all gears)
- Worse under load (up a hill)
- once its above the 2400rpm its back to normal
- OBD scanner shows lambda running very lean in that rev range (lambda 1.25)
- Car is taking out advance to protect itself
Could an injector be stuffing up only at a certain pulse width/percentage?

Also for TRD utes where do you guys find your part numbers for the bits that are different to the normal utes, is there a microfiche website or do you ask your Toyota dealer?

[bricksnmortar]

Swapped the MAF, no change.
I guess it could be the injectors, but odd that they only have an issue around 2000rpm and not up top or down low.
I'm starting to think its more something about the ecu map running it very lean just at that rev range.
I wonder if its hard to see if its got some piggyback module fitted? I'm guessing the ECU is somewhere in behind the glovebox, I'll need to work out if a piggyback sits inside the ecu or clips on the outside somewhere.

[bricksnmortar]

Other thing I might change are the o2 sensors or at least try disconnecting them and see what happens and then maybe buy one and try it in each position (I think there are 4 in total).
I find it a bit hard to believe its the injectors (or pump or pressure reg) since it works fine at higher revs. If the injector had an issue at a particular level, say 30%, it would happen not only in a narrow rev range but at other areas in the fueling map with different loads.

[bricksnmortar]

The OBD app shows that the o2 sensors on each bank return around about the same values for idle, acceleration etc and certainly the same shape graph. I'm going to put those into the low likelihood broken category.
The app also shows that the commanded AFR might drop from 14.7 to 13.7 but the actual goes from 14.7 to 18. So I think it can only be 2 mechanical things and not a control (ECU) or sensor issue. Too much air or too little fuel.
The issue with the too little fuel theory is that it jumps along just fine at 3000, 4000 rpm etc so unlikely to be that. If it was fuel it could be pump, reg or injectors. Next step to rule out fuel is to check the rail pressure. Will see if the OBD tool can tell me, otherwise a gauge if its got an attachment on the rail. If the pressure falls while its coughing I'll know.
The more likely I think is the too much air possibility because just as the blower is building initial boost the engine splutters. Could it be delivering too much boost at low revs? I've tried to research supercharger bypass valves. They seem to just put excess boost back into inlet between MAF and supercharger, ie before the supercharger but not to be counted again by the MAF. That to my mind shouldn't cause it to run lean.
But maybe an air leak upstream of the supercharger would. if would get more air in as the supercharger is developing boost that isn't counted by the MAF.
So in order of next steps I'll check the fuel pressure because its probably easy-ish. I'll have to look for a leak around the supercharger as the most likely. And then if I can't find one, start looking into the supercharger bypass a bit more.

[Ben80]

I would check fuel pressure, its most likely a failing pump

[Mixalis]

bricksnmortar, G'day mate having the same sort of issue with my TRD - did you end up getting closure on what the cause was?,I'm having a solid 2 DTC codes on my TRD which P0171 and P0174 system too lean, it has had Lal the fruit from brand new motor, injectors, all sensors new cats, it's been on a smoke machine no intake leaks, I've even gone as far as disconnecting the O2 sensors which I came up with finding a problem in AFR sensor B1S1 reading -128.00ma with everything disconnected, I believe it's the ECU and I have been quoted $10,838 for a new genuine TRD ECU - any help would be great thank you

[Sideways]

Hi all,

As Ben 80 said - almost certainly the in-tank fuel pump.
Exactly this has happened to me and a few others - dirt/dust gets into the tank (often via the top rollover one-way valve, particularly on LR tanks) and blocks the pre-pump gauze filter. They're essentially a 2 stage pump and the first 'low' stage won't supply enough fuel, starving the engine as the rpms rise - the pump then kicks in at a higher rate and 'catches up'.
Drop the tank, clean, replace the pump with a GENUINE Denso unit (Toyota $1200 - same pump on eBay is less than $200
Cheers

[Mixalis]

Sideways - yes I've gone down this track and replaced that also- and to confirm I bridged the 2 stage fuel pump resistor to see if that made a difference but it also didnt

[Sideways]

Well that's disappointing. The other thing I did when initially diagnosing was to fit 90 degree O2 sensor spacers - did initially fix the check engine light issue but came back and I went searching further. Hope you resolve it.

[Rob_Wood]

Just spotted this thread, how long since you've had an Automatic Transmission Service done? Sounds almost like the bands might need a slight adjustment. Just a thought.