When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
DaleClark's troubleshooting the sequential controls HOW-TO
Hi Guys -
@DriftinJim and I have been talking about this. Lots of people get wrapped up in the sequential control system trying to find a problem and get lost. I'm going to step through a few things to check and work on.
This is going to assume you have a general overview of the sequential system. This will also give some good spots to start but won't hold your hand.
#1 most common problem is a boost leak. If you are letting pressure escape, boost will be down, and if it's down enough the sequential system won't have enough pressure to operate. Most common spots are the 2.75" coupler coming off the Y-pipe, the accordion rubber hose going from the Y-pipe to intercooler, and the 3/4" or so hoses to the charge relief valve and air bypass valve. Replace with silicone hose and a good worm-drive clamp, I recommend Norma-Torro clamps since they don't bite into silicone and get good and tight. This topic has been covered many times, many times by me, search to go deeper.
Next is bad check valves. The stock Mazda check valves fail ALL THE TIME, these are the green/white and green/black stock check valves. They split in two and they let air go both ways. If you search you can find....someone....who sells replacements .
Another one are vacuum lines that are just flat hooked up wrong. You are going to need to print out a big copy of the vacuum diagram (maybe multiple versions), pull the upper intake manifold, and study. Kinko's can print and laminate it for you on 11x17" paper for cheap. If someone working on your car ages ago swapped lines around there's not much that can be done until things are hooked up right.
OK, so you have that covered and you need to go deeper. This is where your boost gauge comes in. Get a vacuum tee (preferably brass) and some extra vacuum hose. We are going to tee into each part of the system with the boost gauge. The gauge will let you see if it's getting the vacuum or boost that it should be.
Let's step through the components:
PRESSURE TANK- After a drive with some boost, you should be able to pull a hose off the pressure tank behind the alternator (either hose) and hear a hiss of pressure escaping. If not, you either have something hooked up wrong, a bad check valve, or a leaky tank (leaky tanks aren't common).
VACUUM TANK - Look at the vacuum diagram, you will see the red colored pipe that goes to nowhere. On the right side looking from the front of the car is a green colored pipe/hose under that red empty pipe. That should have vacuum, if you unplug it you should hear vacuum escaping. If not, bad check valve, bad vacuum tank (I have seen them with the nipple broken off), or something hooked up wrong. The tank is a pain to get out FYI.
CHARGE CONTROL VALVE - This is the butterfly valve in the turbo Y-pipe. There is a metal "can" attached to the arm that actuates the valve. Disconnect the front most hose (should hear a vacuum hiss, this has vacuum from the tank with the car off) and tee your boost gauge in. Start the car and you should see vacuum, when you transition it should show the boost pressure that the secondary turbo is putting out. NOTE - this boost is coming off the back of the Y-pipe so it WILL READ HIGHER THAN NORMAL. You have pressure drop through the intercooler, throttle body, etc. and this is the pure boost the turbo is putting out. Don't freak out, that's OK.
CHARGE RELIEF VALVE - very similar to the charge control valve. Tee your boost gauge in. Should dip into vacuum when it's bypassing the secondary turbo boost before transition then go to read secondary turbo boost after transition.
TURBO CONTROL VALVE - this is the biggie. Hands down this is the one that most people have trouble with since it relies on so much to work - 2 solenoids, the pressure and vacuum tank, and 2 check valves. If any one of those 6 components are bad it won't work.
- There are 2 spots you can tee into. You should be able to get to them with the pressure tank off I think. Look at the vacuum diagram, we have a light blue and a regular blue line coming up from the turbo control valve. Light blue should be vacuum, regular blue should be boost. There are 2 vacuum lines on these circuits to the left of the red empty pipe in the diagram. You can tee in there to see how they work. Closest to the front of the car is BOOST, closest to the rear is VACUUM.
- Both sides should show zero on your boost gauge at idle and low RPM. At transition it should quickly go to vacuum or boost depending on which one you are teed into.
- If not, troubleshoot that side of the system. No boost reading? Pressure tank, check valve, the solenoid, and lines hooked up wrong. No vacuum reading? Vacuum tank, check valve, solenoid, lines hooked up wrong.
- It's also not uncommon for the diaphragm in the turbo control valve to be bad. With it off the car it's easy to test - put your finger over one of the nipples, press the rod in, the rod should stay in then pop back out when you remove your finger. On the car you can do the same thing but it can be harder to get to.
The big take away here should be using your boost gauge for not just reading boost, you can use it to spot check any point in the system for boost or vacuum.
The following are notes I have saved over time taken from different posts/sites/etc
Tee your boost gauge into the nipple that is on the back of the Y-pipe just behind the rear brown Charge Relief Valve's (CRV) hose that is connected to the Y-pipe.
Go for a drive. This is what I saw on my car with this test (My car is 11-8-11 boosting)
3rd gear - WOT
2000 RPM - 0PSI
3000 RPM - 0PSI
3500 RPM - 0PSI
4000 - 4500 RPM - Rolled up to 8 PSI +-1PSI
4500 + RPM 12PSI
What is happening: Page F-84 in the manual
0-4000 RPM - Precontrol controlled by ECU, rear brown CRV off (venting)
Charge Control Valve in y-pipe is on (closed). Turbo Control Actuator in exhaust manifold is off.
4000-4499 RPM -
Precontrol Optimized by ECU, rear brown CRV off, Charge Control Valve in y-pipe is on (closed). Turbo Control actuator in exhaust manifold is off
4500 RPM -
Precontrol fixed (5% open), rear brown CRV is on (closed), and Charge control valve in y-pipe is off (open), Turbo Control actuator in exhaust manifold is on
If you are getting anything close to what I saw with my test, then you can rule out that your precontrol is not working. This means that you should see a build up of boost just before 4500 RPM on the secondary turbo.
If you don't see any boost before 4500 then the precontrol is not working, you have a boost leak, or your charge control valve in y-pipe is open.
If you notice in the above breakdown, the turbo control in exhaust manifold is off before 4500 RPM. The Turbo Control Actuator is the flood gate to the secondary turbo, and if shut, you will only have the fixed 5% of the precontroller pushing the secondary turbo. Does this seem like enough to move 10 PSI? No. So, if your Turbo Control Actuator is not directing exhaust gas to the secondary turbo then you will have a loss of boost on secondary turbo.
If your car is making very low boost or the boost is very slow to come on, you should cap off the secondary turbo inlet and buy/make a boost leak tester and pressurize the primary turbo inlet to hold roughly 12psi to verify the boost isn't leaking out. The original Y-pipe coupler is common to leak along with the small hoses running to y-pipe, intake manifolds, exhaust actuators.
I teed into the vacuum side of the y-pipe charge control actuator with my boost gauge and here are the results:
Car on - Vacuum up to 25 inches - Door shut
750-4500 - Vacuum - Door shut
4500 + Boost up to 12 psi - Door open
What good is this test? Tells you if the charge control door is getting the needed pressure to stay open.
If the car has run recently you should have vacuum built up in the vacuum chamber under the alternator. You should see the y-pipe charge control valve (CCV) rod pulled in with key on and vacuum in tank. If not, turn key on and pull off hose to see if you hear hissing. If not, go to the solenoid and check for operation. If you do, double check valve is faulty by applying vacuum manually with pump. That will cover and assure you CCV is working.
In regards to the actuators on exhaust components, you have the turbo control actuator down bottom on the manifold almost near the bottom of the engine. It moves a flapper that directs exhaust to the primary turbo down low and then to both turbos over 4500rpm. Next, when looking bottom to top is the precontrol actuator which is above that and it will prespool the secondary turbo and give it some exhaust around 4300rpm to get the secondary turbo ready for the transition to both turbos operating together. Then the top actuator is the wastegate which controls boost.
For the turbo control arm that's in the manifold. That one needs to be pushing to the rear when the car is off. As you get to ~4400 rpm, it will pull towards the front of car to let the secondary turbo get airflow. This arm should be long so it pushes the flapper to the rear. Watch this video starting around :45 (his precontrol arm on top right does not seem to be working in this video)
You can see that bottom left arm (turbo control actuator) is pushed to the rear and then it moves to the front around 4400 rpm so the secondary turbo can get exhaust airflow and spool.
The rod above that, the threaded rod, is the precontrol rod that needs to be pretensioned or preloaded. It should be pulled towards the front with extra tension on it or you will lose spool. In order to properly set the length of the turbo precontrol actuator rod you will remove the E-clip that fixes it to the door/flapper. Hold (pull) the door arm to the front so that the door is completely closed. Adjust the length of the actuator rod so that the hole that fits over the pin reveals only half of the pin. When you have accomplished this you will have to use a small vicegrip or similar tool to get some leverage on the rod to pull it to the rear enough in order to place the rod's hole over the arm's pin. You are now pre-tensioning that precontrol flapper so it holds shut against exhaust flow.
The top arm is the wastegate and that one needs to be tight and pulled towards the front tight.
So the top arm and middle arm pull towards the front when car is off, the very bottom arm will be positioned to the rear when car is off.
@DriftinJim and I have been talking about this. Lots of people get wrapped up in the sequential control system trying to find a problem and get lost. I'm going to step through a few things to check and work on.
This is going to assume you have a general overview of the sequential system. This will also give some good spots to start but won't hold your hand.
#1 most common problem is a boost leak. If you are letting pressure escape, boost will be down, and if it's down enough the sequential system won't have enough pressure to operate. Most common spots are the 2.75" coupler coming off the Y-pipe, the accordion rubber hose going from the Y-pipe to intercooler, and the 3/4" or so hoses to the charge relief valve and air bypass valve. Replace with silicone hose and a good worm-drive clamp, I recommend Norma-Torro clamps since they don't bite into silicone and get good and tight. This topic has been covered many times, many times by me, search to go deeper.
Next is bad check valves. The stock Mazda check valves fail ALL THE TIME, these are the green/white and green/black stock check valves. They split in two and they let air go both ways. If you search you can find....someone....who sells replacements .
Another one are vacuum lines that are just flat hooked up wrong. You are going to need to print out a big copy of the vacuum diagram (maybe multiple versions), pull the upper intake manifold, and study. Kinko's can print and laminate it for you on 11x17" paper for cheap. If someone working on your car ages ago swapped lines around there's not much that can be done until things are hooked up right.
OK, so you have that covered and you need to go deeper. This is where your boost gauge comes in. Get a vacuum tee (preferably brass) and some extra vacuum hose. We are going to tee into each part of the system with the boost gauge. The gauge will let you see if it's getting the vacuum or boost that it should be.
Let's step through the components:
PRESSURE TANK- After a drive with some boost, you should be able to pull a hose off the pressure tank behind the alternator (either hose) and hear a hiss of pressure escaping. If not, you either have something hooked up wrong, a bad check valve, or a leaky tank (leaky tanks aren't common).
VACUUM TANK - Look at the vacuum diagram, you will see the red colored pipe that goes to nowhere. On the right side looking from the front of the car is a green colored pipe/hose under that red empty pipe. That should have vacuum, if you unplug it you should hear vacuum escaping. If not, bad check valve, bad vacuum tank (I have seen them with the nipple broken off), or something hooked up wrong. The tank is a pain to get out FYI.
CHARGE CONTROL VALVE - This is the butterfly valve in the turbo Y-pipe. There is a metal "can" attached to the arm that actuates the valve. Disconnect the front most hose (should hear a vacuum hiss, this has vacuum from the tank with the car off) and tee your boost gauge in. Start the car and you should see vacuum, when you transition it should show the boost pressure that the secondary turbo is putting out. NOTE - this boost is coming off the back of the Y-pipe so it WILL READ HIGHER THAN NORMAL. You have pressure drop through the intercooler, throttle body, etc. and this is the pure boost the turbo is putting out. Don't freak out, that's OK.
CHARGE RELIEF VALVE - very similar to the charge control valve. Tee your boost gauge in. Should dip into vacuum when it's bypassing the secondary turbo boost before transition then go to read secondary turbo boost after transition.
TURBO CONTROL VALVE - this is the biggie. Hands down this is the one that most people have trouble with since it relies on so much to work - 2 solenoids, the pressure and vacuum tank, and 2 check valves. If any one of those 6 components are bad it won't work.
- There are 2 spots you can tee into. You should be able to get to them with the pressure tank off I think. Look at the vacuum diagram, we have a light blue and a regular blue line coming up from the turbo control valve. Light blue should be vacuum, regular blue should be boost. There are 2 vacuum lines on these circuits to the left of the red empty pipe in the diagram. You can tee in there to see how they work. Closest to the front of the car is BOOST, closest to the rear is VACUUM.
- Both sides should show zero on your boost gauge at idle and low RPM. At transition it should quickly go to vacuum or boost depending on which one you are teed into.
- If not, troubleshoot that side of the system. No boost reading? Pressure tank, check valve, the solenoid, and lines hooked up wrong. No vacuum reading? Vacuum tank, check valve, solenoid, lines hooked up wrong.
- It's also not uncommon for the diaphragm in the turbo control valve to be bad. With it off the car it's easy to test - put your finger over one of the nipples, press the rod in, the rod should stay in then pop back out when you remove your finger. On the car you can do the same thing but it can be harder to get to.
The big take away here should be using your boost gauge for not just reading boost, you can use it to spot check any point in the system for boost or vacuum.
Good luck!
Dale
Dale, when on the pressure side of the TCV should it stair step up in pressure? When it jumped to boost it was at around 5 psi, then it went up to 10 by 4500 or 5000rpm.
Hrm...I just replaced it back in June (and only put a couple hundred miles since then). To test it for a leak, I'd use the test procedure on F177 and then pressurize and see if it leaks?
Yep, but I'm not 100% sure if that's a problem or not. It could make the TCA start to open before it should, which would mean secondary boost would be slow to build.
Many times with an aftermarket exhaust you can hear the change in note and loudness when the TCA opens, that may be a bit of a clue as well.
New solenoids have been shown to fail, they aren't perfect. Also I don't remember if that solenoid has a specific in and out, if that's reversed that could be a thing.
08-24-21, 02:25 PM
DaleClark's troubleshooting the sequential controls HOW-TO
. 
