Toyota’s unique sequential turbo system found in the 1994-1998 Twin Turbo Supra can be very technical and complicated to the uninitiated. But learning how to troubleshoot 2JZGTE sequential turbos can be easy and very straightforward once you get down to it. Common issues with the 2JZGTE sequential turbos can range from turbos spooling incorrectly, very slowly or not at all. Whether you are fixing an issue or modifying your Toyota VSV system to change how the turbos work, this writeup will help you diagnose your sequential turbo problem.
When your 2JZGTE is having problems boosting on a stock sequential setup, chances are your VSV actuators are to blame. These vacuum switching units help control various items on your 2JZGTE, from sequential turbocharger control to emissions. These VSV control units are basically diaphragm plungers that opens when the right amount of pressure is applied. When one side of the VSV valve receives this pressure, the diaphragm presses against the rod which opens the valve.
Like all plunger style valves, the VSV can become clogged, contaminated or bind when fully extended. We’ll also go over how to test each vacuum unit for proper operation and check that the valve’s resistance is within specification.
Today I’ll be showing you how to troubleshoot 2JZGTE sequential turbos by locating and testing each of the 5 sequential components, and explaining where each VSV is located and how it works.
What is the 2JZGTE Sequential Turbo System?
There’s five components that are needed to properly operate and manage your sequential twin turbocharger setup on your 2JZGTE. Intake Control, Exhaust Control, Exhaust Bypass Control, and the Pressure Tank are the parts you will need to test.
Of these five components, you are interested in just 2 of the controls that control and modulate the sequential turbos on your 2JZGTE. We’ll begin with the wastegate Actuator and the VSV for the wastegate itself.
Locate the wastegate VSV under the primary intake snorkel that leads to your 2JZGTE intake system. Note that there are 2 separate VSV units here, do not confuse the exhaust bypass gas VSV for the wastegate unit.
The wastegate VSV is the first unit we’ll be testing. This vacuum switching unit is controlled by your 2JZ ECU and directly controls the internal wastegates on your 2JZGTE to keep the boost at stock OEM levels (10psi). Remove the wastegate VSV to test the resistance between the two terminals on your wastegate VSV valve.
When measured cold or at 20°C (68°F) the resistance value should be within 22 – 26 Ω using your multimeter of choice. If the resistance shows good between these two terminals, next apply power to the two terminals as shown below.
The next VSV valve we’ll be testing is the Exhaust Gas Bypass Valve (EBV) which is next to the wastegate VSV near the intake side of the engine. This VSV is responsible for spooling the #2 turbo in preparation of turbo transition. When this VSV opens it allows pressure to bleed off into the second turbo, and getting it up to speed until the actuator is fully opened allowing for a smooth engagement of the bigger turbo.
Depending on the year make and model of your engine, this valve may or may not matter. For most OBDII 2JZGTE’s found stateside, this EBV seems to be bypassed which is a modification that pre-1995 Supra owners most commonly do first. JDM Aristo engines that carry a slightly different VSV for the actuation of the second turbo, but the testing procedure remains the same.
The next VSV we’ll be looking at is the Intake Air Control Valve (IACV) which is mounted to the top of the crossover pipe between your turbos. This VSV has two ports one that leads to the actuator arm shown above. This valve is responsible for bleeding off excess boost pressures above the 10psi mark. If your 2JZGTE does not boost over 10psi for whatever reason, check your IACV valve first, as a malfunctioning part will result in limited boost.
For more on how to test your Toyota 2JZ VSV valves, check our How-to article here. If your IACV VSV checks out okay, it’s time to inspect the Exhaust Gas Control Valve (EGCV), which is very different from the bypass valve.
This valve is mounted to your primary turbo’s 02 housing and looks a lot like an internal wastegate. This unit blocks off exhaust gases to prevent overboosting conditions. If you have a problem with boost, this unit may be damaged or the flapper arm and valve inside the exhaust tube may be leaking or broken.
And finally the last part of our How to troubleshoot 2JZGTE Sequential Turbos Guide, is the Pressure Tank that’s located under the intake manifold. This plastic tank is responsible for feeding the IACV VSV valve as well as the EGCV valve.
To test this tank and the pressure that’s supposed to lead from it, check the pressure tank outlet near the front of your 2JZGTE crossover pipe. This vacuum hose is connected to a hard line thats commonly referred to as the “Y pipe” There are 2 vacuum ports on this pressure tank that run along the backside of your 2JZGTE. The lower port on the pressure tank runs to the IACV and EGCV for sequential control. The upper port runs to the front of the engine and exits from the Y pipe vacuum hose.
Inspect both hoses for pressure and check the pressure tank for any leaks that may cause intermittent problems with your boost control. The pressure tank is a common failure for those experiencing inconsistent boost levels, especially for JDM engines.
We hope you learned a thing or two in our How to troubleshoot 2JZGTE Sequential Turbos article, for more 2JZGTE articles like this subscribe to My Pro Street for more technical articles and how-to guides for DIY’ers!
Super nice write up. However without pics for many of us newbies it’s all in vain. I have a stock 2JZ-GTE in a 1999 Aristo. At just below 2000 RPM when the #1 Turbo should be online, there’s engine hesitation. Infact I have to flow the pedal a bit further to have the RPM go up. Then about 3000 RPM I get boost, which probably is the #2 Turbo kicking in.
What could the issue be off head. I have replaced the Intake Air Control Valve from a junk yard twice without testing but no change in this behaviour. What should I look at?
Hi Mustafa, thanks for commenting.
Have you tried disconnecting the wastegate on turbo #1 yet? That should eliminate the possibility of the hesitation being caused by the turbo #1. I wouldn’t look at your IAC first, make sure to go over your VSV and turbo connections first.
My car is completely stock other than the 3″ pipes and the HKS BOV… still running on stock twins.
Since the 6spd swap, I noticed the car has a dead spot when rpm is between 3k-4k where the boost actually drops.
Could this be caused by malfunction of the parts mentioned in this article?
Hi Dave, thanks for commenting on our 2JZ turbo guide.
If you are noticing a big drop off between this RPM range, then yes its very possible there’s a problem with the VSV or sequential turbo control in your Supra / 2JZ. There is a slight delay from the factory however so this could be normal. What ECU are you running on the stock twins? Let us know and we can help steer you in the right direction!
Greetings, so my 2jz gte is overheating, ive notices there’s two coolant lines that run toward the turbos and ive been also having issues with boost. Any ideas? New radiator, new thermostat and new water pump. Thanks
Hi Rigo thanks for reading our guide on 2JZGTE turbo testing.
How bad is your GTE overheating? Are the 2 water lines going to your stock turbos still flowing? Have you tested your thermostat? Is the lower radiator hose warm after a few seconds of starting the engine?
my car is stock and running on stock twins. i had the issue of the #2 turbo not always kicking in and i changed both the IACV and EGCV valve. I tried the TTC parallel mode and borh turbos are working fine and boost presure at normal levels, so i guess i dont have any hoses leak since in parallel mode everything works fine. When i put it back to sequential mode the first turbo wont go more than
0.2 bar and the turbo #2 wont kick in , It only kicks in sometimes at 3-4 gear and after i fully press the pedal to the floor and lift it and repeat that 2-3 times then it kicks in. Is that probable an issue with the reedvalve or the IACV vale since the turbo #1 never goes more than 0.2 bar and only when the turbo #2 kicks in then normal boost presure is achieved? Thanks
Hi Christos, have you tried the VSV troubleshooting guide for your 2JZ turbos? the second turbo not kicking in is a common 2JZ turbo problem.
I would try the valve bypass first. let me know how that turns out
Hi John, thanks for your reply, i tried the VSV troubleshooting only for the IACV and the EGCV valves but Not the bypass valve. Since the first turbo is not boosting, But in parallel mode everything works fine(both turbos boosting) i assume its something with either the reeds or the bypass valve as you mention above.
How do you check if the exhaust bypass vavle has stuck opened?
I would check to make sure your 2JZ turbo reeds are in good order. Because of the vacumn style of actuation involved, any leak or clog is going to prevent that first turbo from spooling. What happens when you eliminate the VSV bypass valve all together? Have you tried that? If not try sending power and ground to the valve with it removed from your 2JZ to see if the bypass is indeed working.
You mean the VSV exhaust bypass valve or the the VSVs for exhaust gaz control and intace air control? i tried eliminating only the VSVs for IACV and EGCV to see if both turbos working fine in parallel mode and they seem to work fine, boost pressure at normal levels. i havent tried to eliminating the VSV bypass valve yet as i assume this is responsible only for the prespool of second turbo.
I also checked my reedvalves yesterday and they seem ok they have only a very tiny gap from housing, from beeing fully closed ( less than 0,5mm) which i am not sure if this can cause any boost problems for turbo num.1 since the flow of the air coming opposite direction to the reeds will force them to completely close that tiny gap.
Start with the VSV bypass valve first, as that’s the easiest to bypass. Once you have eliminated that as the possible culprit to your turbo boost issues, you can move onto the separate VSV valves for intake and exhaust.
Hallo.
I have a stock Toyota Aristo..
then you accelerate normal not hard.. I can hear air going out of the open air filter. Like the wastegate are a little open.. if i accelerator a Little more It goes away. If i push it hard it drive just fine.
it’s the same sound as then you release the throttle.
I have chance a lot of vacum hoses, and check that everything is not leaking..
do you have any idea what that could be..
Hi there Jonas,
quick question, Im assuming your Aristo twin turbo setup is stock. Have you tried to disconnect the VSV valve? Does your secondary turbo spool when this is disconnected?