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Discussion Starter #1
ok.. need help from the guru's in the forum.. I have a 94TT my problem is that every now and then when I floor it WOT my turbos seem to not boost at all and sometimes they kick in just perfectly!... RPM goes high everything goes ok, but when u expect the turbos to kick in they do not, very dissapointing, since I lost to a 2002 Kompressor today. WEIRD thing is that this morning I blew the doors of a mustang cobra SVT.. now to the background.. I have a GCC blow off valve on the car, other than that nothing else done to the turbo system.. I changed all the vaccum hoses this weekend for silicone ones.. (the problem existed PRIOR to the vaccum hose change, I thought I could have a leaking hose somewhere) but I still continue to have the same problem.. and I am in need of experienced advice to track my problem down and possibly help others with the same headache... now I bet tomorrow the turbos will kick in on the way to work.. or then again they may not.. I just finished checkin' all the connections and they were all connected... ran the car again.. WOT.. again no kick from the turbos... any help is greatly appreciated.. thanx in advance...
 
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Discussion Starter #2
Try going TTC with check valves to see if this fixes the problem...maybe it is due to bad vsv's or something like that..
 
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Discussion Starter #3
well, I went WOT this morning and the turbos kicked very nicely.. I'm inclining to think I have bad vsv's.. is there a way to check "individualy" how a vsv is bad??? thanx again..
 
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Discussion Starter #4
When you say they do or don't 'kick-in' are you saying that sometimes they kick in hard and you feel an instantaneous push or sometimes they come on line but you don't feel that instantaneous push but your stiill making boost? Do you have a boost guage? I know you wrote that you do not get boost at all and then some times you do, but what I am asking is do the turbos literally not work sometimes and then other times they work fine?
 
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Discussion Starter #5
no I don't have a boost gauge, I know that would help.. regarding the push... yes I feel an Instantaneous push when it does works.. the power is there and acceleration is great.. when it does not work, like it did during lunch time again, I feel like the car actually boggs down and acceleration is significantly less... has this happened to you?
 
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Discussion Starter #6
one more thing, just ran the car using an outside boost gauge.. while in idle the vacuum ran at 20 inHg, ran the car WOT pressure went up to 8 psi... 1st turbo engages from the kick I get, but once I get to 4K rpm around 60mph... the car boggs down, again thanx for the help..
 
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Discussion Starter #7
Sounds like a loose intercooler hose to me.
 
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Discussion Starter #8
I have the same problem. Sometimes it is there sometimes it's not. If I don't floor it, I get boost all the way into high rpm's but, at WOT it is a crap shoot.

An F150 beat me up a freeway on-ramp yesterday. :madf:

So I ordered the check valves, I pick them up today. Hopefully they will work and I'll get my boost back. Anybody ever have to replace a vsv? How much did the vsv cost?

samymelbourne - I will post back here and let you know what I find out.
 
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Discussion Starter #9
YES, exact same problem!!! well again this morning had power for 1st WOT run, then again bogged down.. maybe due to the car warming up?? going TTC this weekend to check vsv's.. but would like to keep the Sequential going for low end power.. is there a way to individually check the vsv's?? if so how? Wingless did u buy all the vsv's how much did they cost total?? my concern is what if u change the vsv's and the problem still there then the EGCV? the actuator? it's driving me insane too...
 
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Discussion Starter #10
i too have always wondered about this. seems like the same problem intermittant boost. shouldn't you give an error code MIL or something. because when i told the dealership (asked them to check VSV actuators) about this ... the response was no error code ... no problem.
 
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Discussion Starter #11
since this seems to be a recurring problem for all of us who own the MKIV.. and don't want to be beat by F150s how about some help in going about checking:
1) the VSVs themselves
2) EGRV
3) pressure tank
4) IACV
5) Actuators
thanx again.. still lookin' for answers on this throughout the forum
 
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Discussion Starter #12
wingless,

I saw u talked about the IACV in another post.. where exactly is it located? thanx for the info.. how did the new vsv's work?
 
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Discussion Starter #13
I wasn't getting new vsv's today. I was suposed to be getting 2 check valves as described here.

Unfortunately the dildo that works the parts counter didn't physically check his stock so I have to wait till tomorrow to get the check valves.

I am short on time to find a pic of the IACV but it is above and to the left of the top vcv if you are looking at the enginebay from the front of the car.
 
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Discussion Starter #14
well, I just did the TTC using check valves from napa.. they were significantly smaller than the ones recommended at MKIV.com... found out the following... turbo 1 lags a lot under TTC never saw the WOW power from other postings never felt turbo 2 going.. I followed the directions all the way till the permanently ttc mod.. I am still inclined that it's not my number 2 since it does work in the mornings.. when the car is cold.. very weird... and it sux! going to check all intercooling piping check the pressure tank (visually) don't know what else to think it might.. still lost let me know how the TTC went for u.. maybe I need the bigger (toyota) check valves.. :(
 
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Discussion Starter #15
Shit! That sucks! I was hoping the check valves would show that it was a vsv. My second thought is the pressure tank, after that, maybe a slipping tranny. The turbos will not produce boost unless the engine is under load and if the tranny slips the engine isn't under load anymore, thus the turbos would stop boosting. Ya follow me? I am still going to try the Toyota check valves tomorrow. Let me know if your pressure tank and intercooler check out.
 

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If it’s making boost with your first turbo then I don't think it’s a leak, or you would not make any boost. Form what you are saying, it sounds like turbo #2 is not coming on line. Therefore check all VSVs and other items that control the sequential operation. If you tried TTC and still make around 8 psi, then check if your wastegate is working right. I think a bad pressure tank will result in this type of problem, but I’m not 100% on that.
 
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Discussion Starter #17
yup I seriously think it's turbo #2.. AGAIN, this morning (mind I live in florida) the car worked PERFECTLY.. after the 4th WOT run.. again boggin down around 4K RPM... when I did TTC yesterday.. the loss of turbo#1 was extremely noticeable.. back to sequential after that.. Weird thing is in the mornings after I have run the car for more than 20 min.. after I have waited for the TEMPERATURE to climb to 1/4 of way so I don't kill the TURBOS while the car is cold.. for the 1st couple of WOT runs car just runs great... TURBOS kick in wonderfully.. made 100+mph quickly.. then at 5th WOT.. arghhhhhhhhh boggin again... so how do u check the wastegate? how do u check the VSV individually? how do u check the pressure tank? thanx.. still in need of help?? can't stand not to take rx7s
 
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Discussion Starter #18
wingless... how did u'r TTC mod go? well I did the next step on this troubleshoot.. took out the VSVs that lead to the Turbo #2.. checked them by sending 12V current through them.. found out that the VSV for the Wasgewate valve did not CLICK also when I blew air through it.. I was able to hear a very small hiss through it.. so it wasn't totally closed shut.. no click, and no full seal... the other vsv (for the Exhaust Gas Control Valve) did CLICK, this one has three tubes to it.. one to ambient air.. which I blew air pressure to it.. once voltage was applied to it.. I could see air go either one or the other 2 output tubes.. so that one seems ok.. hope this helps on your quest too.. going to Toyota to order the VSV.. will post once I replace it on the car.. later
 
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Discussion Starter #19
The TTC worked great for me bro! The second turbo spools in tandum with the first. The powerband is much more linear and when the turbos spool up, oh shit! I have an auto and the tires broke free at the shift to 1st, 2nd and 3rd. I was doing about 110 by then so I had to slow down. Good to see that you found the problem though. How much is Toyota charging for the VSV? Depending on how much it costs, I might just stay with the TTC.

Good to hear that you found the problem though samy. Let me know how it turns out.
 
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Discussion Starter #20
wingless,

well I went to Toyota today.. the VSV is at $180 oh shit... yes.. that's what I said... now my question to you is.. did u use the check valves ordered from toyota? I bought check valves from NAPA.. maybe they don't work as expected? or maybe I did not do the TTC correctly.. so my question to you is.. how did u exactly do the TTC did u use the TTC from MKIV.. I did, and I stopped at the point before using the wire to hold the actuators open.. hey I appreciate if you give me some info on how u did your TTC thanks for the info.. glad to hear you found yours.. I also have an auto.. how's the lag on both turbos?? are u happy w/ it?? I have a downpipe.. so lag time should be smaller than with a cat back system.. glad to hear your boost'n again!
 
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