Bone stock 1993. Original everything under the hood.

Using the 3rd gear WOT test I am getting 10 psi (or over) until 4500 rpm, a drop to 8 psi, and then while accelerating to the red arc the psi slowly drops to 0 on the gauge. I just installed a turbo gauge a few weeks ago and got 10-8-10. Then after a few days had a slight bleed down problem and found the check valve under vac. tank hand popped line from turbo. Zip tied all unsecured lines I could get to. Fixed boost for a couple of days and then problem reoccurred.

All primary turbo tests seem good. Showing 18-19 inches of vac. at idle. WOT at idle bumps at 7 psi. Under 4500 rpm's in any gear and WOT gets 10 psi. or better. After 4500 rpm slow bleed down to 0.

I have read the FAQ "boost" and "Turbo's" sections, MITYVAC is on the way. Have Mazda Service Manual and am trying to wrap my head around all of the information.

Took a half **** look at the check valves and hoses and could not see anything obvious. While I am absorbing all the information from the above...is there anything that stands out as a culprit to anyone?

And last, is there a range of "normal" pressures one should see on the boost gauge for a given speed? Example: At 50/60/70...mph in "X" gear at cruise you should see "X" in.Hg or psi? All I have come across is idle and 3rd gear WOT spec's.

Thanks,

 

Trying to track down the lack of boost over 4500 rpm. When I went to check the Turbo Control Actuator, I pulled the vac. line off the Turbo Precontrol solenoid and using the Mityvac, tapped into it and attempted to apply a vacuum to see if the actuator arm moved. I got no vacuum. I attempt to pressurize the line, no pressure. I went down to the Precontroller and pulled the pressure line and used the Mityvac to pressurize it to 7 p.s.i., the actuator arm moved and held pressure with a slow leak/return of the arm. Is this normal due to the return spring or is there a leak on the pressure side? The manual does not specify if it is to hold the arm/pressure...just states, that it is to move.

I then removed the vacuum line at the Precontroller and applied 10 p.s.i. to the Precontroller and the actuator arm moved and held steady.

I then plugged the metal line at the bottom (Turbo Precontroller end) and attempted to again obtain a vacuum using the Mityvac from the end of the metal tube that the vac. hose going to the Turbo Precontroller solenoid attaches to. No joy. The metal line would not give a vacuum or hold any pressure. Is having a hole/crack in these metal tubes a common problem? It looks like I will need to route a new vacuum line from the Precontroller to the Precontroller solenoid.

Are there any other solutions to this or maybe something I missed?

Thanks,

 

The TCA operates on both vacuum and pressure - so you would need both to activate it. You can use the KOKO test on it - but I don't think it is your problem.

The precontrol actuator is pressure driven.

Have you tried simple tests like the couplers on the IC and stock y-pipe?

 

Also, is your CRV closing at transition? If it remains open, you would lose all boost.

 

I'm stupid. I meant to say that when I tested the Turbo Control Actuator...I pulled the vacuum hose to it, off of the Turbo Precontrol solenoid valve. I attached the Mityvac to the hose (from solenoid to TCA) and could not make vacuum. I also attempted to push air through the line to pressurize...zero results.

To rule out the TCA itself, I pulled the pressure line going in to the TCA OFF THE METAL LINE and pressurized the TCA through the short piece of rubber hose. The actuator moved fully into the TCA with 7 p.s.i. BUT very slowly extended out and the pressure slowly dropped a couple of pounds over a minute of so. IS THIS NORMAL? I am thinking it is fighting the internal spring and it might be normal for the actuator to extend. I then pulled the vacuum line AT THE TCA off the metal line and pulled vacuum which moved the actuator arm into the TCA. The vacuum and actuator held steady until released.

Now, with the TCA vacum line still disconnected (from the solenoid and TCA), I attempted to apply vacuum and pressure to the METAL LINE with one end plugged. I could do neither...which indicates to me that the metal line from the solenoid to the TCA has a leak. Sound right?

Just wondering if anyone else had seen/heard this problem?

 

restricted exhaust. ie the pre-cat or main cat converter. boost seems normal including transition except it trails off at higher rpms

 

CRV...with the engine off I checked the valve (along with the BOV) like so...I pulled the hose to the air cleaner and could freely move air through CRV. I then removed the "A" line to the CRV which released pressure(? heard a whooshing sound) and I then could not pull or push air through CRV. I applied vacuum to "A" port and could again freely push/pull air through valve.

Not sure if that tells you (or me) what you need to know.

 

With only a little over 19K on the car I doubt she's plugged...although I've seen cat's come loose on bike exhausts and muck up the works. Also, I would expect to see the boost stay up longer than 4,500 rpm's before tapering off. Maybe even not get to 10 if it is that restricted. At 4,500 rpm's it drops off from 10 p.s.i. to 8 and then ends up at 0 by 7,000 rpm's. Plus a couple of weeks ago I was getting 10-8-10.

 

ok so the pattern is 10-8-8-falls to 0? the dip at transition is normal. what is the reading at 6500?

 

At 6500 in 3rd gear if I recall (did not write this stuff down) it was around 3 p.s.i.. Maybe.

As for my other inquiry as to the Turbo Control vacuum...forget it. I'm a dumbass. I was using the factory vacuum diagram and buggered myself. Just found the "colored" version and can see the PRECONTROL solenoid has not a damn thing to do with the TURBO CONTROL ACTUATOR vacuum. Color is a great tool...whoever took the time and effort to do that...thanks.

moconnor...you tried to point out the error of my path...but I was too dumb to see it. Too many "actuator's" with "control" in the name confused me...heh...more than one is too many at the moment!

This newbie-rotorary-twin-turbo-rat's nest thing is a real mind bender. Again my apologies for taking up bandwidth by having my head up my ***. Tomorrow WILL be a better day.

 

Pattern should be 10-8-10 rolling down to perhaps 8 psi at ~8k rpm with the stock exhaust system.

It is almost definitely a leak.

I'm still betting on IC or y-pipe couplers - the latter being the most likely.

 

The precontrol does not connect to the turbo control solenoid. It connects to the precontrol actuator. If you tee into either the wastegate or precontrol lines you will not learn anything with your Mityvac because the lines are vented in both directions.

The slow bleed from these lines in one direction is because there is a restrictor orifice in the line between the compressor elbow and the precontrol actuator. Ditto for the wastegate.

 

OK, so now you're testing the TCA all alone. A good test, for sure.

It should hold pressure indefinitely. In operation, it has 10psi on one side and 20inHg on the other. This is similar to if you would apply 20psi with the Mityvac.

I would replace the TCA and see if the problem goes away. A leaking TCA is consistent with your boost symptoms. It will cause the TC door to swing shut as it leaks pressure, slowing the exhaust flow over the turbos and killing your boost above 4500.

 

Well...the good news is I think I may have found my problem. The one-way check valve for the Turbo Control Actuator (under pressure tank) would leak down about 5 inHg every 30 seconds. Would not hold pressure either.

The bad news is I did not stop there in checking the one-ways and ended up snapping off the nipple to the Double Throttle Control solenoid. My engine bay is now littered with chipped enamel from my teeth. As easy as the nip came off...I figure I'm not the first igit to perform this trick. WTF's idea was it to make those nipples outa plastic? There's a special place in Mazda hell for that guy. Deep breath...count to 10....maybe 20.

Other than a new/used solenoid and manifold gasket, is there any other "must have/do" items that I'll need before proceeding? Of course I will be upgrading hoses and check valves that get in the way.

And although I know I can find the solenoid and gasket, advice as to the some of the better places to send my money would be appreciated.


Humbly,

 

Some items that I believe are worth doing when in the rats nest:
- FPD
- Fuel line recall kit
- Send injectors for ultrasonic cleaning and o-ring replacement
- Coolant hoses (particularly the block-throttle body hose)
- Replace thermoswitch with 2nd gen thermoswitch
- Cut away crispy wiring harness insulation and rewrap with silicone self-fusing tape
- Test all solenoids

While your car has extremely low mileage, I personally would err on the safe side. Age and temperature work together to cause problems.

You mentioned you found a slow leak in both the check valve and TCA. I assume you will replace both.

Dave

 

Dave (or anyone else for that matter),

The DT solenoid, manifold gaskets, VITON tubing, FD thermoswitch and Mallory cooling hose kit arrived today. VITON check valves are on the way. I decide to take the aggressive approach and change out or upgrade as many items as practical. I have ordered or am ordering shortly the following:

1. New FPD (is a gasket needed?)
2. Fuel line recall kit (but if this has been done, is it necessary to replace?)
3. Injector O's and grommets (is there a VITON kit for these?)
4. New OEM plug wires (I have new plugs)
5. New OEM thermostat & gasket.
6. Aluminum AST
7. Efini "Y" tube upgrade
8. O2 sensor (OEM)
9. K&N air filter (stock box)
10. New belts
11. Air Control Valve gasket (just in case)
12. New PCV valve
13. New Purge Control check valve
14. Have self sealing silicon tape already

Atkinsrotary.com has a injector kit with a few more large O-rings and diffusers. Is this kit more desirable than just the O-rings and grommets? Or are the rings & grom's sufficient? Ray Crowe gave me a good price on the O-ring's and grommets...but I see where Rotary Performance has a RP O-ring kit for $16. Are these the same quality as the OEM Mazda stuff?

My goal is to maintain as close to the "stock" configuration as I can on this car. What I do "upgrade" I want to be able to switch back to the stock configuration with no hassles if I so desire. I'm not looking to pump up the HP's, just going for the reliability side of things. Am I on the right track? Biting off more than I can chew (I gotta big mouth)? Did I miss anything? Gaskets?

 

1. The FPD has a small o-ring on it already.
2. If it's been done, not necessary. But very good to have the replacement hoses on hand. You can determine if the recall was done by calling Mazda customer service and providing the VIN.
3. For the grommets, no. I'm not sure what the original material is for the OEM o-rings, so Viton may in fact not be an upgrade here. Or maybe it is. There are more grades of o-ring material out there than you can imagine. Some vendors (Atkins) have measured the stock o-rings and found aftermarket replacements for less money - again, I'm not sure if the material is better but it's at least sufficient.
11. You'll need that gasket

I recommend adding the FC thermoswitch too. It's about $30. Ray Crowe knows which part is compatible.

Is your car the one that had the leaking TCA? If so you definitely need to get a good used one and change that out at some point. If you're on the phone with Ray ask him for a price on that part just for *****-n-giggles.

Dave

 

Thanks again Dave...and...way ahead of you, TCA $556. I am going to test it again, it "appeared" to leak on the pressure side. But, I was jammed under the car and getting the test hose on the TCA was a PITA...I may have not had a good seal on the tube. I'll give it another go (practice makes perfect) with the Mityvac before putting out feelers for a used or new TCA.

If the "FC" thermoswitch is the 185F switch for kicking the fan on...that is the one I got from Ray. Just a brain fart typo above...hate the fact you only have 30 minutes to edit posts with this site!

 

Another off the wall question....not having torn apart one of the engines before...is there a logical way of tackling the replacing of the components (listed above)?

I guess my biggest question is whether to drain the cooling system and change the 14 hoses first...or tackle the vac. hose/rat's nest before yanking anything else. Or do I put the Efini Y pipe in and then...???

I figure whichever way I go, the UIM needs to come off 1st and then go from there. Just trying to save myself doubling back...any advice?