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Trouble Shooting Sequential Issues (need some advice)
I'm looking for someone who is well-versed with the factory sequentials and their associated control system.
I've gone through the FAQs for the diagnostics, and done a fair bit of troubleshooting. Every time I find what seems to be a problem or part of the problem and repair it, I get even more confused. Here's what my symptoms have been, and what I have done so far with what results:
First issue: 10psi of boost with primary turbo, dropping to 3-5psi at the transition, and tapering off to about 2psi by redline. First problem found: Vacuum nipple on the charge control actuator (CCA) was broken off, so it wasn't receiving vacuum signal. I had a spare that I checked with a MityVac, confirmed as good, and put on the car. Symptoms after fix: 10-8-10 boost pattern during the first pull. Shift into next gear at redline, no boost. Let the RPM drop below 3000, do a pull again, and I have a 10-8-10 pattern once.
After this, I pulled the upper intake manifold.
Second problem found: Found a vacuum line being crushed/pinched by the intake manifold. Replaced the line, and rerouted it so it was no longer being pinched. Third problem found: Pulled off the turbo control solenoid (vacuum) that's right by the junction of the upper and lower intake manifold. Checked it with a MityVac, and found that the solenoid was leaking from the dump port (port C) with the cap on it every time I clicked the relay with 12V. I replaced the factory cap on port C with a vacuum nipple cap and a spring clamp. Checked it again with the MityVac, and it was no longer losing vacuum when the relay switched vacuum between port A and port B. Symptoms after fix: Essentially non-sequential. No boost until transition, then all the boost directly after the transition. This continues until the car begins to heat soak, and once that happens, my issue basically reverses. After I've been driving the car, I'll get boost from the primary and no boost with the secondary. Once I shut the car off and let it sit, it will "reset" and I'll have ONLY the secondary turbo when the car is cold, and when it's hot, I have ONLY the primary turbo.
Also, just to point out, there's an older thread regarding a fix for a sticky turbo control pressure solenoid that involves splicing a check valve between the line going to the TCS and the line going to the pressure tank. I have done this fix, and it seemingly is making no difference. I have also checked all of my check valves with the MityVac and confirmed them as being good.
I'm really confused with this issue, and I'm looking for some advice on how to continue my trouble shooting process. It seems like the problem got worse after I rectified some issues.
Let me start by saying I applaud you for the well written post.
Symptoms after fix: 10-8-10 boost pattern during the first pull. Shift into next gear at redline, no boost. Let the RPM drop below 3000, do a pull again, and I have a 10-8-10 pattern once.
Checked it with a MityVac, and found that the solenoid was leaking from the dump port (port C) with the cap on it every time I clicked the relay with 12V. I replaced the factory cap on port C with a vacuum nipple cap and a spring clamp. Checked it again with the MityVac, and it was no longer losing vacuum when the relay switched vacuum between port A and port B.
~ Can you clarify the solenoid you’re referring to? Solenoid where the lim and uim meet is called “turbo control “ and is only supposed to be a two port that directs vacuum to the center port of the actuator. Having said that, the factory caps are actually small filters that allow air to pass through. You cannot put a vacuum cap and seal off those parts on any three port solenoid. Take the picture from this thread, and circle which solenoid you are referring to so I can take a look. https://www.rx7club.com/3rd-generati...-turbo-749702/
The problem is, you need to test the solenoids at both room temp and 190° ish. I’ve seen them work cold, but not hot, and Vice versa. You probably don’t want to hear this, but it’s probably time to replace all of the solenoid‘s that contribute to the sequential system with new ones. They are not overly expensive and it saves a lot of time and energy.
Also, make sure your check valves are working correctly and oriented in the correct direction.
It outlines that this solenoid is in fact a 3-way valve. The testing procedure says to check it with 25inhg of vacuum, then click the relay and make sure it doesn’t leak while being powered. Mine dropped pressure every time I clicked the relay, and found that it was leaking from port C, which is the cap. I assumed the cap was a vacuum cap, and I’m just now realizing that the post probably meant to make sure the solenoid didn’t leak while it was being energized. Not necessarily that it wouldn’t leak any time the relay was clicked, which wouldn’t really make sense. Thankfully I kept that cap.
I’ll pull the UIM off again, put the factory cap back on, and test the solenoid at temperature. While while I’m in there, I’ll probably go ahead and check the precontrol and wastegate solenoids because they’re easy to get to.
Thanks again for the response, and I’ll be sure to update the thread with my findings!
Yep you are on a roll. Replace that solenoid if it tests bad and you are all set.
It switches between vacuum and atmospheric pressure. One port goes to the TCA, one to the vacuum tank, one is a breather cap so that's atmosphere. Normal driving the line to the TCA is connected to atmosphere so it's at rest. After transition TCA is connected to vacuum to make one side of the diaphragm move (the other side is the pressure side). After RPM's drop it should open back up and vent that vacuum to atmosphere to close the TCA.
So! I pulled the UIM back off, and I yanked off the turbo control solenoid (TCS). I had driven the car shortly before I tore it back apart. First I checked the vacuum unenergized. It held 25inhg, but seemed to be leaking very slowly. Not sure if it’s the solenoid or my vacuum pump. I went to go energize it to test it again (after reinstalling the factory cap on port C) and I couldn’t get the relay to click. It was still warm to the touch at this point, so I blew on it a few times, and tried again. Got the relay to click, and same result as unenergized.
To be sure that it wasn’t a connectivity due to my janky wiring apparatus, I stuck it in the oven at 200 degrees F and let it sit for about 5 minutes. Removed the solenoid, and again the relay wasn’t clicking when I powered it. I then put the solenoid in the freezer, and left it energized. After about a minute and a half, I heard it click.
I repeated this test again exactly the same as the first time, and had the exact same result. Seems to me that the TCS is losing connection to power and/or ground as it gets hot.
I had a really similar issue a long while back with an EM1 Civic Si I used to have, where the main relay would lose connection as it got hot and cut power to the fuel pump. It was due to a solder joint that had formed a crack and expanded as it heated up. I repaired the solder joint, and never had an issue again.
Since I know this solenoid is junk, I’m going to try and source a new one (If anyone has a part number, it would be greatly appreciated), but in the mean time, I’ll pop it apart and see if there are any visibly damaged solder joints or anything like that, and possibly try to repair it just for ***** and giggs.
Thanks again for the input, and I’ll update the thread again when I get a new one in the car.
The part number for that is ~ N3A1-18-741. It should come complete with the cap.
You are understanding why people have so much trouble with the sequential system. You’re definitely going about it in the correct method of troubleshooting, you just got in your own head a bit. It’s vital to test them @ temperature for the very reason you’ve discovered. I guess we all start to forget that these components are almost thirty years old now. Mileage is not even a factor any longer, just age. Hell, I even had a brand new one that would stick when hot. I personally enjoy a sequential car and think it’s worth the effort to get them working properly.
Sorry for the absence, it took a while for the new solenoid to arrive. Last night, I got around to installing the new turbo control solenoid. Took the car for a quick spin, and now I’m back to making 5psi after the transition. I’m truly stumped, I was almost positive that was my issue, and now it’s behaving almost exactly as it was before I began troubleshooting anything at all. It’s back to behaving consistently, which is a good thing, I just don’t understand how it went from making 10 pounds up top occasionally with a bad TCS and now it never makes 10 pounds up top with a brand new one. I’m going to pull it back apart, and check the new one I put in. Pretty unfortunate news
Ok, so you’re on the right track now. I figured you had more than one issue going on. Double check the new solenoid works properly at room temperature and 200° first. I’ve seen brand new ones act goofy ( ask me how I know). Then check the charge relief labeled “H”. If this one bleeds air after translation it will show that symptom. Check charge control “F” which controls the butterfly on the y pipe. Make sure that moves freely. You can check that with a little hand vac right at the port. I would also check the air bypass valve ( blow off valve ) to make sure that’s working correctly also.
Just a thought, because I forgot to ask, have you smoke tested the intake to make sure you don’t have a leak?
I’ll check those things out today. I have already replaced the charge control actuator with a known good one. Also, I have not smoke tested the intake system, although before I replaced the turbo control solenoid, it was making 10psi intermittently. The primary turbo also makes 10psi consistently, so I don’t think it has a boost leak that’s substantial, although it’s worth looking into.
Probably not. If you’re making five psi consistently it must be bleeding somewhere. I would focus on transition control first. If solenoids test good, we can move on to mechanical like turbo control actuator and pre control actuator.
Thanks for the insight, I just replaced the CRV with a known good one (checked right before I installed it), and while I was in there, I checked the charge control actuator, and it seems to move freely when I apply light vacuum to it with my mityvac. Drove the car with the new CRV, and there doesn’t seem to be a change. Next I’ll pull the UIM again and check my new turbo control solenoid for issues. If it checks out, I’ll move onto the rats nest and check out all of the relevant rack solenoids in there.
There supposed to be a white paint mark on the arm of the Turbo control actuator arm. Normally it’s so dirty you can’t see it any longer. It lines up with the bracket that mounts it. All that does is hold preload on it. Did you make sure the vacuum didn’t bleed off on that after 30 seconds or so? I’ve seen that cir clip fall off too. That’s what’s going to direct exhaust gas to the secondary turbo. So if that or the butterfly are not operating correctly you will only see partial boost. If it’s making 10 psi on the primary turbo no problem, I wouldn’t think the door being was out of adjustment.
What ecu are you running?
In the first picture I’m pointing to the pre-control,
In the second picture I’m pointing to the turbo control actuator flapper this should be open after transition. During primary operation this will be closed tight against the turbo manifold. After transition it should be open allowing exhaust gas to flow into the second turbo. Double check that the control arm is holding open. That sees both pressure and vacuum. It switches between the two which aids in helping open and close it.
You could always buy all new solenoids and silicone vacuum lines, redo the whole system, and not have to worry about it in 15+ years. If one part fails, the rest is not far behind, and everything is still available new in the box.
This is the route I took, even though I had no major boost problems. My only problem was my secondary turbo didn't kick on in 3rd and 4th gear or something like that.
This is the expensive route, but it's necessary unless you plan on selling the car soon. Then yes, take the cheaper way.
I wouldn’t call troubleshooting the problem in a calculated way to repair what’s wrong “taking the cheaper way ”. I would however say throwing parts at it till it’s fixed is a misuse of time, energy and expense. Yrmv tho.
When you replace a shock on a car, do you replace all 4? Or only replace the 1 shock that's leaking? When you replace tires, is it better to do all 4? Do you replace 1 spark plug or all of them?
I wouldn't say "throwing parts at it"; it's more like preventive maintenance because it's a complex system that can't have 1 leak or 1 bad solenoid, so the expense part is justified. Everything has to be perfect for the turbos to work correctly. For the time and energy portion, it would take less time and energy if you replaced everything that needs to be replaced, (which is everything.) Lol. It would take more time to troubleshoot.
This system specifically isn't easy to troubleshoot or worth troubleshooting.
Off topic, but to the OP. If you do decided to replace everything, I highly recommend replacing the fuel injector O-rings. I believe Mazda did a recall because they would leak.
For the time and energy portion, it would take less time and energy if you replaced everything that needs to be replaced, (which is everything.) Lol. It would take more time to troubleshoot.
This system specifically isn't easy to troubleshoot or with troubleshooting.
Without derailing this thread, this is why people like you and I will never see eye to eye. We just look at this from opposite ends. Tho I can understand this thought process. No I would not just change one of the few items you listed. You’re distorting the comparison I made to justify throwing parts at something in hoping it sticks. The sequential system isn’t a set of tires or shocks either. I definitely agree that all the parts need to work perfectly to make the system function correctly. But replacement of everything because of one part is ludacris .
For you, those statements may be correct and if that’s your chosen route for repair great! Nothing wrong with preventive maintenance. The reality is you can’t say “which is everything” because you really don’t know. Others don’t find it to be such a time consuming and daunting task as you’ve made it out to be. It’s really not that bad after you’ve studied and understand how the system functions.
Anywho, back on topic. I applaud the OP for investing the energy in troubleshooting the issue and working to repair it.
When you replace a shock on a car, do you replace all 4? Or only replace the 1 shock that's leaking? When you replace tires, is it better to do all 4? Do you replace 1 spark plug or all of them?
I wouldn't say "throwing parts at it"; it's more like preventive maintenance because it's a complex system that can't have 1 leak or 1 bad solenoid, so the expense part is justified. Everything has to be perfect for the turbos to work correctly. For the time and energy portion, it would take less time and energy if you replaced everything that needs to be replaced, (which is everything.) Lol. It would take more time to troubleshoot.
This system specifically isn't easy to troubleshoot or worth troubleshooting.
Off topic, but to the OP. If you do decided to replace everything, I highly recommend replacing the fuel injector O-rings. I believe Mazda did a recall because they would leak.
Those aren't very good example, the systems you refer to generally have the same workload all the time, that's why they are replaced altogether, and tires are usually done as a pair unless it is 4WD.
You are assuming everything in the sequential system get the same workload all the time and therefore they need to be replace all at once, this is like thinking the only way to fix a circuit board is to replace all its component, which is not true.
It's about understanding how the system work, and replace the part(s) that failed.
To OP, I think an intake smoke test is worth trying. When I got my FD 12 yrs ago it used to only boost up to 7psi, while troubleshooting I found a boost leak at the LIM, it was missing a stud. Not to say that was the only root cause, as I did test all the solenoid and replaced the weak one. I think I replaced half of them, and I have a working sequential system till this day.
One big take away here is to tee the boost gauge into each part of the turbo control system and see what it's doing. Instead of blindly guessing or troubleshooting you can get actual data. Tee into the turbo control valve vacuum side, see if it properly switches between vacuum and atmospheric pressure. It does? You just confirmed the solenoid, vacuum tank, check valve, and all lines on that side are good, now move to the next thing. You don't see it? You know where to start looking.
As far as the "replace everything in there" I think there are definitely two sides to it. A new solenoid isn't a guaranteed good solenoid, some of them have had issues right out of the box. Also it's just silly to me to throw out solenoids that are fine. It's also a somewhat advanced job to do a full replacement, there's lots of other problems that can be caused by trying to go into the rat's nest. Mixing up vacuum hoses, breaking other hoses, breaking other solenoids, breaking electrical connectors, you name it. It's also possible it's just some mixed up vacuum hoses or a bad check valve too.
Again, this is why my technique of teeing the boost gauge into each component of the system is a good idea. Get hard evidence as to what isn't acting like it should.
It's good that we have different ideas to bounce off each other. Yes, I agree, replacing everything sounds ludicrous but hear me out. Get the new parts now; they will only be here for a short period. Everything will cost 2K, but you won't have to worry about it for 15+ years. Also, save all the old solenoids, so you have spares for when these parts become hard to find in the future.
I would lean more toward only replacing the broken parts if all the pieces were in stock in 15 years. As I said, it's not worth troubleshooting because you're screwing your future self up by not replacing everything now while you still can. It's only a matter of time before the rest of the system fails.
Originally Posted by DaleClark
As far as the "replace everything in there" I think there are definitely two sides to it. A new solenoid isn't a guaranteed good solenoid, some of them have had issues right out of the box. Also it's just silly to me to throw out solenoids that are fine. It's also a somewhat advanced job to do a full replacement, there's lots of other problems that can be caused by trying to go into the rat's nest. Mixing up vacuum hoses, breaking other hoses, breaking other solenoids, breaking electrical connectors, you name it. It's also possible it's just some mixed up vacuum hoses or a bad check valve too.
Hi Dale, you helped me out years ago. Glad to see you're still on the forums.
The new solenoid out of the box is true, but it didn't go through many heat cycles, so better than the old one, right? A complete replacement of the whole system is more straightforward than finding the problem of one, two, or maybe three components because there are too many variables that you could be chasing. I think it's less risky that something will go wrong if you start from "zero" and redo the system yourself, 1 vacuum, 1 solenoid, and 1 check valve at a time. Hell, I made it simple to track hoses; I'd fill in the hose I installed in Microsoft paint using the famous vacuum hose picture. Lol. Also, before I removed the old hoses, I would label each hose and pipe with the same number with numbered zip ties you can get off amazon. (It's used for labeling chickens)
So, if you've done everything correctly by replacing every hose, check valve, and solenoid, you'll be golden for years to come.
This is my way of thinking, and I stand by it. If this car was only 8 years old, I'd chase the one or two components, but everything is old with miles. It's time the car gets a refresh.
It's about understanding how the system work, and replace the part(s) that failed.
Not to sound sarcastic, but the system can give 2 ***** if you understand it or not. The part you didn't replace next to the new one is not far from failing either.
My way of thinking could be the training I received from my old job; one part goes wrong, and we send the whole unit in for a replacement. We didn't crack open the electronics and solder in a new piece (Although that is cooler and more rewarding). Nothing beats all new parts when something is this old.
Not to sound sarcastic, but the system can give 2 ***** if you understand it or not. The part you didn't replace next to the new one is not far from failing either.
My way of thinking could be the training I received from my old job; one part goes wrong, and we send the whole unit in for a replacement. We didn't crack open the electronics and solder in a new piece (Although that is cooler and more rewarding). Nothing beats all new parts when something is this old.
Thats why you need to know how things work, if it is failing it will fail your test, it’s not rocket science. Replace everything seems to be the norm nowadays, I work with field tech that deal with hundred thousand dollar equipment and they do the same thing. If you are lucky that will work, but many times they will call and said everything replaced and issue still there, because they have been looking at the wrong place all along.
What I’m trying to say is, you can replace the whole solenoid rack and still have issue… if that’s not the issue all along.
My way of thinking could be the training I received from my old job; one part goes wrong, and we send the whole unit in for a replacement.
I can understand this approach. It’s exactly how I train people at work ( I have a small Commercial Electrical business ). As a for instance, if we’re replacing a ballast in a fixture that doesn’t work, we don’t leave the old light bulbs with a new ballast. We replace everything. If it was just bad tubes, we just replace those and move on. It stops delays and allows for fewer call backs. Not a bad way in respect to business. If the op was taking it to a shop it’s a 50/50 shot they would follow this methodology. Having said that, if I were to go into a customers building and one of the two sewage pumps was bad, I’d only replace the bad one. It’s normally the main pump that sees all the workload. The other we test, verify it works, and move on. All I’m saying is there’s a time and place for each thought process. Glad we can agree to disagree
^Good point. You can't just say "boost problems = replace everything" that that will fix it. It's quite possible you will spend the money and do the work and STILL have the same problem. Figure out the root cause FIRST then start replacing parts.
It's not uncommon to have mixed up vacuum lines from previous work. Also boost leaks are still the #1 cause of boost problems out there in my experience.
If you are lucky that will work, but many times they will call and said everything replaced and issue still there, because they have been looking at the wrong place all along.
What I’m trying to say is, you can replace the whole solenoid rack and still have issue… if that’s not the issue all along.
This has been my experience as well. I’ve seen individuals replace all of the solenoids to find out it was totally something else. Like in proper settings in their new ECU, or having a boost leak, or the turbo control actuator cir clip rotting off and the arm is disconnected. I think if more people follow the troubleshooting approach as a process, they would be a lot better off.
09-23-22, 12:17 PM
