So then I was test driving my car after getting her back from the body shop. Carefully warming her up, easing on all gears until well into running time.

#1 turbo kicks in great, but during transitition or when the #2 should kick in, the car doesn't pull. It accelerates slowly as if there's no boost at all. I let go of the throttle for a sec, then hit it again, then the #2 turbo kicks in fully. This goes on for most of the gears, during which I never went WOT, at the most probably 85%-95% throttle. A friend tells me that a vaccuum hose might be disconnected therefore causing the lack of boost in #2 turbo.

Does that sound right?

Everything else is working beautifully and before the accident the car was also running/boosting great.

-Dan

 

Sounds like a bad one way check valve...(Little green filter next to the vacuum chamber)

 

Is this dangerous to leave it running unfixed? My friend says it's fine, I just won't be able to boost 2nd turbo.

But yes, thanks for the suggestion, I will go check that now.

 

Ditto on that...I had the exact same problem and never saw it until I built up enough ***** to pull of my UIM...it was clear as day...Seems the previous owner tried to glue one of the valves back together unsuccessfully. as soon as I replaced it I was back to normal boost again. You can pull off the pressure chamber and check there first. this is where mine was and really didn't require pulling the UIM...

Hope this is your prob cuz it's an easy fix.

 

can you show a pic of that check valve??

 

the black and green cylindrical looking thing inline with the blue hose is the check valve that gave me problems...You can get to that one by removing the pressure chamber.

 

Thanks for all the help. Actually I couldn't sleep without checking the engine bay one more time and found out there's this vacuum hose that's coming from the front turbo that was ripped around where the tiny clamp is.

I don't know what it's called, but it's like 10in long, one of the smaller ones, and there's another one just like it right next to it but this one is around 5in long.

I had to rip out the entire intake pieces, all piping and work all the way on the bottom, my back was sore as **** when I was done and went straight to bed since it was nearly 2am. Got up this morning and did a quick test on the freeway (downshifting from 5-4 @ 65mph and 2nd turbo kicked in nice and hard.

I'm a happy camper once more.

-Dan

 

Dan,
Have you done a 3rd gear WOT test? if you haven't get on a nice open piece of road and cruize in 3rd grear at 35mph...stomp on the pedal and carefully watch your boost and the road at the same time...if you have truly fixed it you should see your boost gauge shoot up to 10psi (providing you are stock or close to it) then right around 4500rmp there's a slight dip in the boost gauge to 8psi and it shoots back up to 10psi again...when you see it shoot up to 10psi the second time, that's when you know your secondary turbo has kicked in.

 

thanks for the pic apneablue. i'll have to check up on that myself,.

 

yup check valves for sure. change all 4 of them while you're at it.

 

I wouldnt drive it like that if it were mine, It would seem that it would put twice the strain on the primary turbo without having the help of the second turbo.
When I had a similar problem my primary turbo never shut down it still boosted but it was obvious that the secondary wasny helping.
Look at the hose diagram and double check for the "turbo actuator" & "precontrol actuator", they are the 2 hoses right in front just to the right of the little actuators that bolt to the uim and jund like an inch behind the alternator, they have a real abrupt bend like 90degree because the steel hoses both face upwards, they are real obvious, those two guys were the sole problem for my boost problem which was very similar to yours...

 

Oh, also, I reommend doing the simplification, its real easy and I can look under my UIM and see that every single vacuum hose is working correctly just by lifting the hood...

 

Now that I think about it mr rx7tt sounds right, if you have to let off the gas and then accell to get sec boost it must be one of the check valves, letting of the gas would create vacuum and probably temporarily fix your prob but then the valve gets stuck and you need the vacuum decel to fix it again...! Some of you guys are genious'

 

Classic turbo control vacuum leak symptoms. Check this reference. There are details on how to systematically check the different places where you could be losing vacuum for the turbo control system. A Mityvac vacuum pump will be a big help.

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

BTW apneablue was referring to the pressure chamber check valve. The vacuum chamber check valve line is on a different hose. If you have a Mityvac, you can hook the pump up to the the hoses with and without the check valves to see if the lines hold vacuum, before replacing check valves. You might find that the vacuum chamber itself is bad (cracked and leaking).

As you'll find by reading the above site you'll need to check the vacuum lines originating from the vacuum chamber to be sure they're connected properly (see schematic diagram).

Check the vacuum lines connecting the turbo control actuator (buried underneath the twin turbos) and the rat's nest.

Check the charge relief valve (commonly known as the secondary turbo blow off valve--which it is not--it's a charge relief valve), and the air bypass valve (commonly known as the primary turbo blow-off valve--which it is).

You might also have a bad turbo control solenoid or bad wastegate/precontrol solenoids (see diagram in reference site).

Worst case is that you have a bad turbo control actuator (expensive part, $1200 from the dealer, $600 from Mazdaspeed Motorsports Development).

As you can see it's not as simple as just replacing check valves. Some members have been lucky, and check valves are all they've had to replace to restore secondary turbo operation. Don't count on being that lucky...

 

Well all I know is that i replaced this hose of some sort and now it's boosting fine again. I'm having a friend identify what it is and I'll get back to you guys.

Check valves...................



-Dan

 

i have the same problem dave akdr said it could be sensor called a cp something like that i dont know...he said the sensor plays dumb and is common.It is in just 1st gear the second turbo does not come on once i shift into 2nd it works...

 

This is new. What is the "CP"??

 

i dont know he said something like that....i really wasnt paying attention he said a bunch of letters..LOL

 

i would have guessed it would have been the check valve leading from the vacuum chamber to the manifold