No primary boost (well seeing maybe 1-2psi on the gauge), however at approx 4000rpm, secondary boost comes online strong and holds! This tells me the primary is producing boost / secondary is prespooling? Is the charge relief getting stuck open or something?

What makes this quite unusual is sometimes, the car will boost perfectly on the primary (and secondary), then sometimes nothing at all on the primary.

The car is running basically stock with sequential setup. Hoping some of the knowledgable guys will chime in with suggestions / pointers.

 

The CRV will be open until around 4000 rpms when it closes to allow the secondary turbo to build boost before coming online. However, your Charge Control should be closed until around 4500 rpms keeping the primary and secondary separated. If the Charge Control isn't working, it will allow the primary to join the secondary turbo while the CRV is open, thus venting most of your primary boost until the CRV closes around 4000 rpms:

http://www.autosportracetech.com/RX-...erOverview.htm

I would start with checking the Charge Control system.

 

Thanks Mahjik... what are the common failure items with the charge control system off hand? I guess the solenoid, but is it likely the charge control valve is stuck open? What's unusual is the fact that this problem is intermittent, i.e. sometimes (though less often now) the turbo operation is perfectly normal 10-8-10 pattern. Most times nothing until ~4000rpm.

 

IMO, the fact that it 'sometimes' works doesn't seem like a mechanical problem. I would wager on the Charge Control solenoid not functioning properly. One quick way to test it is to switch that solenoid with one of the emissions solenoids (something like one that attaches to the ACV) and see if it fixes it.

 

Cheers Mahjik.. that's exactly what I'm gonna do. I reckon it is the solenoid itself. Why - I don't know, there's only about 60k miles on this car. I guess it would explain why there was 'intermittent' boost problems at first before primary failed completely. I also notice that the wax rod it staying "out" on the CCV - I'm gonna wire it shut ("in") and see if I get primary - then it's definitely the solenoid I reckon.

I pulled the hose from the vacuum chamber (the one with just one hose to it), and it vented air - I thought there should be "vacuum" in this chamber?

 

It might be me, but air rushing in vs. air rushing out sound a lot alike. Follow that line back into the metal tree, then follow the metal line past a 'tee' to a check valve. That valve should be pointing toward the UIM (it has an arrow printed on it), then remove the valve and ensure the air cannot flow against the arrow direction.

Dave

 

The TCA valve in the exhuast manifold could be held (stuck) open in the secondary position causing the system to function in a quasi non-sequential mode. Not much would happen until the revs get high enough to build some boost and the rpms are around 4500 where the system will switch the rest of the sequential controls over.

If this is occurring, then a likely culprit is the pressure side Turbo Control solenoid labeled "E" in the rat's nest. It is the 3rd one back with the orange wire connector on it. This particular solenoid has been problematic on these cars and sometimes sticks, unable to relieve pressure and causing this kind of problem. Other TCA related possibilities include the vacuum side Turbo control solenoid (located on the ACV) and the TCA (actuator) itself. If I remeber correctly, the latter actuator has a rather strong return spring in it which should close the TCA valve if the vacuum lines to it are disconnected..

Hope this helps.

 

this was happening to me but i was only seeing 1 to 3 psi on the secondary turbo. it turned out it was the rubber hose leading to the bov on the secondary turbo. it was cracked really bad and when i took it off it crumbled into peices! replaced it and it was fine. hope this helps

 

Did the vac hose job when I rebuilt the engine.

Apart from playing with the wax rod on the CCV yesterday, when I started and drove the car today I got full, reliable boost on the primary. It has me a bit stumped now as to whether it's the CCNT solenoid or the CCV itself. What do you guys think?

 

The CCV is a pneumatic actuator. There is a diaphragm and spring inside, but no wax rod.

Your CCV may have been sticking - which it can sometimes do since it doesn't have any lubrication. But then again if it's the CC solenoid, it may only misbehave when hot.

Next time it misbehaves, try the KOKO test. www.fd3s.net/boost_test.html If the CCV or solenoid is at fault, you should see it here.

Dave

 

I have seen intermittent primary boost failure caused by faulty check valves. Definitely check or replace them.

 

If there was a kink in the rubber hose going to the CCV would it give problems like this? The really big hose that goes to the air box is what im talking about.,

 

The CRV goes to the airbox, not the CCV. The CCV is the one in the y-pipe.

Dave

 

Thanks Dave for your valued pointers so far.. just to confirm yes the PFC does operate things as per the stock ECU - i.e. the KOKO test will actuate the CCV.

As for the CCV sticking - I think its the solenoid myself. As I say, I can push the rod on the CCV actuator in and out effortlessly (it springs back out). When I had primary boost, when key on, they rod pulled in (valve closed) and key off the rod popped out.

Over the weekend I had reliable primary boost for a while, but the next day when I drove the car, had reliable boost, and then about 5 miles later - no boost on the primary again. Hopped out to do a quick KOKO test and the the actuator rod was just staying out.

So.. I'm almost posative it's the CCNT solenoid, what do you think?

 

ky7,

Try switching the solenoid with one of the emissions solenoids (EGR or Switching ones) and try your car for a few days. It's possible that you switch a bad solenoid for another bad solenoid but I rarely have heard of the emission solenoids failing. However, the Charge Control and Charge Relief solenoids fail quite often (most likely because of how much they are used in comparison to the emission solenoids).

 

Thanks Mahjik.. will do. One issue is that this particular car is a series 7, so it has the vacuum box (or black box as it's referred to here). I'm having difficulty sourcing the individual solenoids (and help / suggestions appreciated), and it looks like I may have to purchase the entire black box new with integrated solenoids and check valves. It's a bummer, cause you can take the box apart to replace things, so I will do this to switch the CCNT solenoid. I might just use an pre series 7 solenoid and hook it up directly, for testing purposes (the solenoid connectors are different on the older FD compared to the integrated ones in the vacuum box).

 

I suspect the pre-series 7 solenoid will work just fine. There are pics of those all over this forum. You could always get some used ones from someone on the forum classifieds.

You can get those separately from Mazda around $60USD each. The price for a whole box would be ghastly, although it should solve solenoid problems well out into the future.

Dave

 

Indeed. I'm trying to source this vacuum box as we speak with great difficulty. Is there any Japan based "suppliers" who will help out on this I wonder?

As you say - the older solenoid should work, at least for testing so I will try this. Thanks Dave.

 

I would consult with the European regional forum. At least run a couple of searches.

Dave

 

Thanks again Dave. I actually managed to source whatever I need from Mazda Japan now, through an associate over there.

It's very strange, but the primary boost issue seems to have just vanished! I tested everything and it all checked out, except for the CCNT solenoid itself. I wonder was it just a bit of crud or something stuck in the solenoid - or perhaps the actuator was acting up, but it's fine now? The only work I carried out on the car since was relocating the air temp sensor. Weird ****!