I have been having this problem with my sequential system since I bought my car, but thanks to the PFC, I might have found the cause... I just need some help interpreting the info.

When I get on it and the system makes the transition to the secondary, the boost will drop and build very slowly and will not recover until I get off the throttle or deaccelerate. Well, today while looking at the [Sensor/SW] display on the commander, I noticed the TCN (turbo control) switch comes on and "sticks" when the problem occurs. The only way to "unstick" it is to deaccelerate and then boost works again.

So my question is what is the TCN and what part of the system does it control? The fact that it "sticks" mean it's bad? Any help would be great.

 

The turbo control solenoid (3rd from the front under the UIM) controls the turbo control actuator. This actuator is located on the bottom-front of the turbo manifold. It controls the flow of exhaust gas to just the primary turbo in prior to transition and opens up to direct exhaust to the primary and secondary a little before the transition and during the transition to allow the turbos to run in non-seq.

By the looks of it, the solenoid needs to be replaced. While you're under there, you might as well test all the other solenoids with a 12V PSU.

 

Oh yeah, after reading your post over it could also be a leaking pressure/vaccum chamber since it works okay if you let the throttle off for a bit.

 

i posted about this problem in another thread.

I think the PFC seems to highlight any existing problems with vaccum/solenoids.

My FD was running without boost problems until I had the PFC installed.

It will go up to 10psi and at around 6k RPMs it will drop to 7psi.

ANd when I shift, sometimes it will get stuck with little or no boost.

I have to let off the pedal and/or put it in neutral to "reset" it.

 

batman you sure the vac tank is holding and the check valve is ok?

 

i have the same problem except for the fact that im running the stock ecu. Im thinking either the turbo control solenoids or the vacuum chamber and its check valve.I suppose ill have to dig in there and check things out. Anyone have a cliffs notes explanation on how to check the solenoids out? I just replaced all of them less than a year ago with new ones but you can never tell. I have a digital multimeter. Just need to know what specs I should be looking for.
Thanx

 

Thanks.
Do you know the correct readings for the solenoids? Also, are all the solenoids the same as far as the function of them? I have a lot of spare solenoids that came from another Mazda engine and they appear to be exactly the same as the ones on the 7.

 

There are a couple things to check: the voltage drop over the solenoid coil, and the operation of the solenoid. The multimeter will read the voltage drop (resistance) with no issues. You'll need a 12V (low current - not your battery power) source to see if the valves switch correctly with/without 12V. Download the manual and see the Emissions section - the solenoid test values are found scattered in there.

Dave

 

Any other solutions?

 

Obviously your car needs some vacuum to operate and therefore you need to release throttle a bit. Check for leaking one-way check valves and vacuum hoses that hold vacuum.

Batman: I have similar problem as you - I think TCA is at fault. It requires both vacuum and boost to operate

 

From what I gathered from the PFC, I have an electrical issue/bad solenoid. Will the PFC detect a vacuum leak?

 

I have this problem... have for years with nobody able to fix it. I currently have a PFC, but it also happened with the PFS purple. I have new turbos (99), a new turbo control actuator, I replaced the TCS and used new vacuum hoses, and both my vacuum and pressure chambers check out.

Currently, the transition "back" to sequential mode works better with the pressure line to the actuator DISCONECTED. I must conclude that after the pressure (along with vacuum) is applied to move the actuator, that it doesn't release the pressure right away after i let off, and so it has a hard time transitioning back.... The TCA doesn't really require vac and pres. to opperate, it requires both to opperate QUICKLY. Using the vacuum line only makes it slower, but at least it actually works. It's really ******* irritating.

 

I've also noticed my exhaust tone will change when this occurs. It gets louder as if a valve was opened or something. Could it have something to do with the wastegate?

 

i have a problem close to that. when i get on it in 1st the boost just drops off then when i shift i have no bost in second shift again and no boost in 3rd until late in the rpm ranges. if i shift from first at 4500 and 2nd from 4500 i get boost allthe way through 3rd and 4th. does any one know the cause of that and i also only build about 7 psi.

 

That's because the flapper door in the manifold is still open because the TCA didn't close it... its a louder, resonatting farty sound right?

 

i have the same damn problem.looks like were all having the same issues.I guess its not a turbo problem.I wonder what we can do about this little issue.
Cant we adjust the rod in oder to keep it closed at all times? what would this do to the turbo system?

 

Yep... now, what can I do to fix this problem?

 

Wish I knew. Heck, I wish PFS, KDR, or RP had known... none of them could fix it. I see Dave Disney has a thread on advanced tech with the ssame problem, and he's fixed the same things I have... we'll see if he can find anything.

 

who is dave disney?
anyone contact gotham racing to see if they can help?

 

Yep.

That's something I noticed.

No boost = louder exhaust.

 

He's been around for a long time.. from back in the "big list" days.

 

i get the same thing as well.the exhaust tone is much louder when the problem occurs.Which means this tca rod isnt closing

 

I doubt it's something anyone can diagnose over the phone... like I say, I've had mine at PFS, KDR, RP, and a couple others, as well as talked to experts on the phone, and no fix. I'll probably go single before it ever gets fixed...

 

have you changed out the two solenoids that control the tca?
and also the vacuum chamber and check valve?

 

Right.

EVERYONE WITH THIS PROBLEM: Go home tonight, jack up the car, and remove the line going to the pressure side of the actuator (it's on the side). Mine actually works BETTER this way, and I think it's because the pressure isn't getting released to reset the actuator, so it works slowly, but it works, using just the vacuum line.

At least we'll see if we all have the same issue.