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Discussion Starter #1
Hi Guys,

I am now a new owner of a MKIV Supra RZ-S (Manual) I picked it up on Friday, I'll try and get some pictures sorted soon! over the last couple of days i have noticed that my second turbo doesnt kick in at around 4k rpm. As i reach 4k rpm in every gear.. the boost generated by the first turbo just drops.

I had a look this lunch time at all the pipes going to both the IACV VSV and the IACV actuator, i also checked the all the pipes going to both the EGCV VSV and the EGCV actuator, and everything seems fine..

When i came home from work I had a quick play around in the engine, and i have noticed the IACV Actuator is closed in idle, which is normal, and when you rev the engine to around 4k rpm, the Actuator opens up as you would expect, you can actually see this operate when the engine is idle, which suggest to me that both the IACV Actuator and the IACV VSV are both working, and the air flow pressure to the IACV Actuator and VSV is fine..

However the EGCV Actuator doesnt open up, whether it opens when the engine is in idle or under load I wouldn't know.. actually, I don't think it would, because it relies on the manifold pressure to open up the EGCV Actuator! I wonder if the EGCV VSV is working.. does anyone know of a way to test the EGCV VSV solenoid?

Wish I had a bicycle pump handy to test the big EGCV Actuator..

I am getting there I suppose..

would anyone have any suggestions or advice on what the problem could be? the Supra has only done 21k miles so very unlikely that its a blown turbo!!!

Cheers,

James
 

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Discussion Starter #2
By the way, the Supra does have a missing Traction Control Relay on the driverside (left side facing the car)

There are only two Relays in the box, both are for the ABS, would the missing Trac relay have anything to do with the problem i am having?

Cheers
James
 

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Put the car in TTC. If the turbos boost fine then you know its a VSV.
 

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Discussion Starter #4
Cheers i have thought about doing that, looks like i should now! how easy is the EGCV VSV to replace, cuz it looks like a biatch to get at from the top..
 

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en hopup veritas
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I posted this a while back about checking for no boost conditions and issues...I hope it helps abit

OK guys...I am new to this forum so go easy on me! I have however had a great deal of experience with boost problems regarding the sequential system. Assuming turbo has not failed itself diagnosing boost pressure loss at high rpm is really not too dificult. According to the NCF (new car feature book) and the factory shop manual start by checking the VSVs controlling turbos themselves. You can actually take a 9v battery and after removing the VSVs apply current to the VSV terminals themselves. You should hear them click when the circuit is completed and released. Next check to the see that the resistance on the VSVs is within .38-.46ohms. When checking VSVs don't forget the one under the intake manifold. Next the two vacuum controlled valves should open at approx 6.7-7.5psi. I have always checked them with a vacuum pump. If one or more of these functions are not happening then you know what your dealing with. If these VSVs and control valves are all operating there are a few other areas that could be at fault. If the ECU does not see a boost pressure signal then the ECU will keep the fuel pump in low voltage modes and in some cases (I have dealt with this on 2 occasions) it will lock out the #2 turbo. Another aspect to look at is to make sure the pressure tank is holding pressure. If this is not the case then the #2 turbo will fail to spool, or you will have to roll into the throttle slowly to get the #2 turbo to actually spool. This gives the pressure tank enough time to fill enough to send pressure to the control valves to actuate the #2 turbo. Yet another aspect is something I just got done fighting. There are 2 vacuum lines that run behind the head that go to and from the pressure tank. If the transmission or rear crossmember is removed the back of the engine must be supported. If it is allowed to rock back against the firewall (as it was in the case if this Supra) the hardline part of the two lines can be pinched, crushed or cracked. The other thing that can happen is that the soft part of the line can be cut by various sharp parts back behind the head. In the case of the last Supra I fixed, UPRD (sorry, not to framiliar with who they are or what they normally do) had done a clutch and trans rebuild (badly I might add, left a bolt out of the bellhousing and left 2 rear crossmember bolts loose...plus it shifts horribly.....oh well thats another story) and not supported the back of the block when removing the engine and it caused one of the vacuum lines clamps to cut the softline directly below it. The clamp acted like a cutting devise. This hole prevented to the pressure tank from building pressure and caused the #2 turbo not to spool. The car would go full rich waiting #2 to spool and the car would churn out black smoke. It had nothing to do with the turbo itself......ok now I feel retarded.....I just got done proof reading this post, reading all the posts by others and then the results of the HomeRocks problems and I feel dumb. I am gonna post this anyways because I am sure alot of you have had boost pressure problems and I am very sure alot of you have done tranny/ clutch jobs and might have run into problems shortly after the job was completed. As for turbo rebuilds, I have had great luck with Performance Techniques. I have used them for 4 years, rebuilding CT-26s and CT-12s and never had a failure. Well for whoever reads this I hope this helps a few people out there.

Matt
 

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Discussion Starter #6
Well I have now put the car in TTC mode and both turbo's are not coming on at all!

When the Supra was in Sequential mode the first turbo would boost, and the second turbo wouldnt start and all the boost would escape stopping both turbos

Now in TTC mode neither turbo will boost! and it feels probably worst than a NA there is no power at all but still runs smoothly does that make any sense at all?

When i took the big Air intake hose off to get at the pipes to the EGCV valve and VSV there isnt any sign of oil! which is a good sign.

So whats going on? possible leak near the pressure tank under the manifold?
 

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Discussion Starter #7
Here's the latest, the Supra is now back in sequential and the First turbo is working again!

Now i am back to square one, with the second turbo not spooling up!

Before i reconnected the Inlet pressure to the EGCV VSV which comes directly from the "Pressure Surge Tank" i tried to blow in it, and it wouldnt give and it felt like it was blocked, which is what you would expect.. and if i blow hard into the pipe and fold the pipe so that it traps the air, then release the pipe, it hisses, so all the pipes to the pressure tank sound like they are ok..

So now im thinking the EGCV Actuator is leaking badly because the Pressure Tank has now manage to regenerate enough pressure to activate IAVC Actuator in sequential mode again. But it couldnt activate the IAVC Actuator while the pressure line was fed directly to both the IAVC Actuator and the EGCV Actuator (from the same line) Since the EGCV Actuator might be leaking,
and when the Supra was in TTC configuration all the pressure which would have opened up the IAVC actuator escaped from the EGCV Actuator instead.

What do ya think?
 

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My Sympathies Big Time

I was in your exact position for many months. Exact same symptoms. Exact, but my car had 45K miles. I couldn't figure out what was wrong--unless it was the second turbo.

I finally followed the advice of a lot of guys on the Forum, where a favorite saying is, "time to go single." And when Altered Atrmosphere pulled my stock twins to put in a PowerHouse Racing Street Kit, it was clear that number two was really dead. It wasn't the VSVs/actuators.

I hope you're not in that boat, but there is a time when you have to assume the worst and move on.
 

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Discussion Starter #9
Surely the 2nd turbo cant have blown, it has only done 20k miles, and the car is just under 5 yrs old..

i hope its the EGCV Actuator is shot,
 
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Osso said:
Surely the 2nd turbo cant have blown, it has only done 20k miles, and the car is just under 5 yrs old..

i hope its the EGCV Actuator is shot,
depends how the previous owner treated it really :O

alot of high reving while the engines cold will do it :|
 

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Discussion Starter #11
I got a pump today and Checked the EGCV Actuator and the IACV Acturator and they are both ok, the rod extends and stay extended until the pressure is removed!

I have managed to find the pressure tank, and i can feel the 2 pipes that connect to the pressure tank, and they are not loose!

I also took off both Air intake hose and the intercooler hose which goes into the intercooler and there is no sign of oil anywhere...

However i had a look at the radiator cap, and it kinda looked like water, and the cap it self had some brownish deposits on it.. i then had a look at the radiator filler hole and its extremely low and looks like there's water at the bottom? I thought this stuff was supposed to be a reddish ribena colour? surely this is where the coolant goes?

could the ECU be cutting the power to both turbos because the coollant is low? I've not noticed any engine warning lights while traveling
 

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It might be a VSV issue. Continue testing until you’ve completely figured out the problem. Even if it turns out to be a blown turbo (let's hope not), you can probably buy a set off somebody that has gone single for a good price.

Here’s some info I typed out in a previous post of mine, where I was trying to help another Supra owner with this problem. This seems to be a common occurrence.

“There are four VSVs that control the timing of your second turbo. Find each one and test it. If they're all good, test the pressure tank. If it's good, I would go step by step through the entire routing of the system and make sure that hoses are in good shape, not broken, actuators are working, etc.

To test the VSVs, you'll need to figure out which side is the inlet and which is the outlet (a service manual would be a HUGE help here - I'm currently away from mine, so bear with me). The first step would be to make sure they're closed when they're supposed to be. So, put some air into the inlet and make sure it doesn't leak. You can blow through a straw or use some sort of pump, whichever works for you. I would use a small amount of psi from a pump / compressor, since the psi out of your lungs is probably very little. There are two kinds of VSVs - one will not allow any air to pass through when it's closed. The other type will send the air out through a filter. Either way, air should not come out of the outlet.

Next, you'll need to make sure it's opening properly. To do that, apply a 12V power source to it. I use a set of wires that I hook up to the battery and probe the terminals on the VSV (be careful here – it’s a tight spot). You should be able to hear the VSV click over and air should then pass through the outlet.

Next, check your pressure tank. The manual tells you step by step what to do. You have to apply x amount of pressure to the tank and it shouldn't leak. The next step is to apply x amount of vaccum to the tank and it shouldn't leak. But I don't remember the x values. I'll repost when I get home if you'd like.”

That was it for that post. If you need to know those values, let me know and I can look them up for you. Another way to check the pressure tank is to pull the hoses off the small VSV on top of the engine right after driving the car. If you hear a rush of air as you pull the hoses, then the pressure tank is doing it's job and you are probably looking at a VSV issue. If you don't hear air, then either suspect that VSV or the pressure tank / lines leading to / from it.

This will probably take you several hours of testing, but it might save you some money in the long run. I’ve been there, though. My second turbo didn’t work when I first purchased my Supra. I know how frustrating it is.

BTW, your coolant should be red. If it's just water, you'll probably want to drain it and put a coolant / water mixture in there. Actually, if you're seeing rust, you might want to flush the system. I seriously doubt your coolant has anything to do with your boost issues, though. To my knowledge, the ECU doesn't monitor that sort of thing.

Get your engine codes checked by someone with a scan tool. There may be more things going on that your little check engine light is trying to tell you!

Good luck!
 

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Discussion Starter #13
Hiya thanks for your reply sounds like it could be of help! please please please I would be very grateful if you could tell me how to go about testing my pressure tank in more detail, or even scan the manual pages for the pressure tank, because after going TTC using the pressure lines to EGVC VSV, IAVC VSV and feeding them directly to the EGVC and IACV actuators bypassing both VSV's I don't think the pressure tank had enough pressure to open them both.

I have not tried testing the VSV's electrically just yet, but I didn't realize that there were two types of VSV's, I assume that the two VSV's which let air through a filter are the IACV VSV and the EGVC VSV, because from what I've seen on the IACV VSV there is a little black cap with some holes in it attached somewhat loosely to the VSV.. I guess this is where the pressure escapes when the VSV is closed?

I know for a fact that the EGVC Actuator and the IACV Actuator are both working, after applying pressure earlier today with a small pump.. the rod on both actuators would remain open until the pressure was removed.

Another thing, do some Actuators operate on vacuum and others operate under pressure? if so, which ones?

Regards
James
 

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Discussion Starter #14
I assume that finding the inlets to the VSV's would be quite easy if you follow the metal pipes around near the top IACV VSV since they are pressurized, well should be!
 

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Discussion Starter #15
one more thing, sorry, how do you know where the negative and possitive connections are on a VSV? or does it not matter?
 

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MKIV intervention needed
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my no. one went bad at 50K mi. i went to a t66 and never looked back the single setup is just awesome.
 
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