Waste gate actuator

ogre07 · Mar 10, 2011

Hi all:

I am a newbie getting rapidly out of my depth. I just bought a 97lexus LX450 and i keep popping a check engine light and it codes P0171. I get lots of opinions so I took it to the shop. Good thing too since it turned out NOT to be the MAS sensor OR the O2 sensor OR a loose clamp OR a loose wing nut.

Turns out it is a torn diaphragm on the waste gate actuator in my TRD supercharger. It is 8 years old and Toyota no longer supports the unit. Anybody have an idea? Somebody might have a spare... Or be parting a unit... or know of an alternative that might fit. I know some folks, more mechanical than I, replace the actuator to get more boost. The one they took out would be just fine for me.

If I can't find a fix I may have to pull the supercharger cause I can't pass a smog test like this.

Thanks for your help

Bob Christie (ogre07)

landtank · Mar 10, 2011

i'll jump in and say that I've not read about your problem. I'm not so familiar with a waste gate on a SC. Can you give more details on the truck itself like year?

ppc · Mar 11, 2011

On the TRD supercharger that is called the bypass actuator

Here is a link to Magnuson that use the Eaton M90.
Magna Charger manufacturers intercooled supercharging systems for late model GM and Ford cars, trucks and SUVs utilizing OEM quality Eaton hybrid superchargers.

Also CDAN might have some good information if not a source.

S.CarolinaFZJ80 · Mar 11, 2011

Check the link above. Magnuson M90 is the supercharger that TRD used. They just added their own TRD parts to make it fit on the 4.5L.
I would first replace the 1 1/2"hose & use new clamps, if that doesn't work replace the bypass valve diaphram.
Magnuson is great to deal with. I had them refurbish a used supercharger that I bought last year and they had it back to me in a week.

I would pull that SC off and clean out that bypass valve too as it is probably gummed up from oil blow by.

Oh and its MAF sensor not MAS. P0171 means you are running lean and most likely have an intake or vacuum leak. I would also check all of the rubber intake hoses/clamps for the supercharger and ensure a good seal before buying a new bypass valve. Also, check all of your smaller vacuum tubing. You will need to clear the check engine light code and see if it returns after all of this.
If not search P0171 on Mud and it will point you in the right direction for what to check next. Also, get a Factory Service Manual for your vehicle.

Just my $0.02

MountainBum · Mar 11, 2011

DON'T RUN IT HARD OR WIDE OPEN THROTTLE!!!!! You're lean condition is casued by the SC over boosting due to the by-pass valve not opening at the preset boost level. Good thing that the by-pass valve also is blowing out boost through the busted diaphram so it's not too bad. It is actuated by a vacuum line full of boost from the SC which at the present time is just blowing through. As above, contact the Manufacturer and they should be able to get you a new wastegate actuator/by-pass valve.

S.CarolinaFZJ80 · Mar 11, 2011

Sorry I didn't make that clear but I thought it was obvious that ogre07 should not drive it like this.
,
Thanks MountainBum

landtank · Mar 11, 2011

I thought the bypass valve was used only during idling times so there would be no boost at that time. But outside idling it was closed. And isn't boost dependent on pulley size and is not governed like on a turbo with a waste gate.

S.CarolinaFZJ80 · Mar 11, 2011

Landtank - You are correct Rick.
Vacuum keeps the bypass valve open thus bypassing boost at idle. So when you go into boost the valve closes. I would asume that when you go into any amount of boost that it would close completely as there is no vacuum at that time. Wouldn't the throttle be the determining factor in how much boost you get, based upon air/fuel ratio & the corresponding increase in RPM, up to the max amount of boost which is determined by the pulley size? With my stock TRD pulley I consistently get 6 lbs. of boost max.

So I suppose that ogre07's bypass valve apparently stuck closed at idle and during boost applications causing the ECU to lean the fuel based upon faulty data because the MAF is reading a lower air content than what is entering the combustion chamber due to an intake leak or vacuum leak downstream of the MAF sensor.

ogre07 - It wouldn't hurt to take out the MAF and at least clean it off. It may be dirty or oily from blow by oil or an overly olied K & N air filter at one point in it's life, causing faulty data to be sent to the ECU.

Oh and buy Landtank's MAF housing and get the newer style MAF sensor. It works great and corrects some short comings of the older style MAF!

landtank · Mar 11, 2011

the thing about the PO171 is that you usually need what ever is wrong to also be erratic in nature.

A dirty MAF sensor can do this because the readings will jump around erratically and the ECU can't respond fast enough to satisfy the O2 sensor.

This is the same thing with a tear in the intake tube. The engine moves around creating a varying sized vacuum leak or even a fuel pump or fuel filter where it will cause erratic fuel delivery.

My point is if the problem is constant then the ECU will likely adapt without out this error code until it reaches the limits of it's ability to adapt then it will give an entirely different error.

So in short I'd double check the diaphragm problem and possibly look somewhere else for the cause of the PO171.

S.CarolinaFZJ80 · Oct 14, 2024

Bumping this old thread.

My bypass valve finally developed a vacuum leak, after 14 years. The SC was purchased used and I had Magnusson rebuild it. I have no idea if they replaced the bypass valve or diaphragm then.

The TRD kit used an Eaton M90 supercharger, later Magnusson but Magnusson doesn't support them any longer. They referred me to SuperchargersOnline.com for parts for their older discontinued units.

I placed a call with them and am awaiting their tech department to return my call. I'll post up the part number once I figure it out.

S.CarolinaFZJ80 · Oct 19, 2024

I verified the correct replacement part. The "waste gate actuator" / "boost bypass valve" is actually referred to as a bypass actuator.

It is enroute from superchargersonline and I'll post up the install pics.

The sales guy there was awesome to deal with. His name is Nergal.

Here's the link to the bypass actuator and some detailed pics of the actuator.