First of all, here's the car's description: 94 Touring FD, all-stock exept for aluminum AST, downpipe, hi-flow cat and a boost guage. The car has 67000km (50xxx miles).

The problem was not gradual. It starter at one time and now doing it all the time the circumstances are met for the problem to occur.

The problem is that there is no boost at all, but only in these circumstances:
When I floor it from low rpm (lets say idle to 2500 RPM), there is no problem at all. Nice 10-8-10 patern, all the way to the red line. Then I shift, let's say, in second gear (now near 4000 rpm). No boost at all. Nothing. Every time I floor it from a RPM of 3500 or higher, I get no boost at all, but if I floor it from low RPMs, I get nice boost all the way to the redline. If I floor it from around 3000-3500, sometimes I get some boost in higher RPMs, but not much (around 5 psi) but this is not every time. The problem is really RPM related and not vacuum related as I did the test to let the vacuum build up at a steady 4000rpm then floor it, no boost.

What I did/checked to date:
-checked for apparent disconnected vac lines, nothing.
-removes UIM to inspect rats nest, found 2 cracked vac lines, repared them. Changed UIM gasket and elbow/TB o-ring.
-tested all 5 check valves, they worked well, I tested them with a vacuum pump. They hold pressure/let the pressure go according to the arrow stamped on them.
-tested boost tank, no leaks.

Re-instaled everyting.
Same problem.

Need help please!!!!

 

did you try the double throttle control assembly and solenoid? i had a similar problem and it ended up being a cracked nipple on the double throttle control solenoid and some burned up vac line.

 

when you say it only doesnt create boost from 3500 + rpm, do you test that after going above 4500 rpm then dropping down to 3.5k then flooring it? or does it also do it if you just ease up to 3500 rpm without boosting then THEN floor it?

damn that reply was all over the place.um..pretty much, if you havnt already, just ease on the gas and dont let boost build, just ease really slowuntil you get to 3500 rpm and THEN floor it. and see what happens

 

Maybe I could stick the double throttle open and try it? When I removed the UIM, I didnt see anything wrong with it, the lines were not cracked and tight.

 

Not really sure what you mean... When I talked about 3500-4000 rpm, this is approximate... I'm not sure what it will do if I ease up to 3500rpm then floor it as this rpm range is some kind of a grey area, it won't do the same thing everytime... But if I ease up to let's say 4000 rpm from idle then floor it, I won't have any boost.

I will try to do more testings.


Anymore things I could check at the same time?


Forgot to mention that the car is a 5 speed.

 

Ok I did some more testing, here's what I found: If I ease it up to any RPM, boost is ok until redline. I mean... If I bring the rpm slowly (vacuum) up to whatever RPM then floor it, boost is ok. Then I shift at redline, no more boost. In order to get back the boost, I then have to lower the rpm to 2500. Lowering it to 3000 does not work. Even if I let it run at 4000 or whatever in vacuum mode, as soon as the rpm havent gone to 2500, it won't boost. The proplem seems to occur only when I redline it. If I floor it ant get 10 psi but get off my foot from the gas before redline then it's ok, and I don't need to drop the rpm to 2500 to get the boost back.

It realy looks like the problem is there only when I redline it. You know, when you want do make a quick start, you redline it and then shift... no more boost. have to drop the RPM to 2500.

Let me know if it's not clear... english is not my main language, so It may sound funny...

Please help me on this one!

 

Please guys! I need some help!

 

I see two possibilities:
1) sticking solenoids
2) bad check valves

I would start by buying a tee fitting (like item 5463K181 from www.mcmaster.com) and use it to connect adjacent to the vacuum chamber. Then do some test runs and observe if you have plenty of vacuum (more than 15inHg) during your boosting. The vacuum will decrease during boost while the solenoids operate, but should never reach a low value and should always recharge immediately after letting off the throttle.

Then reconnect it inline with the pressure chamber and ensure it's always got pressure following the first time you boost. The amount may change, but it should always have at least 5-10psi available.

If it passes those tests, I would suspect the solenoids themselves. Again, move the tee to the line leading to the front of the turbo control actuator. It should apply full (10psi) pressure from 4500rpm and up, release when you let off the throttle, and open up again at 4500. The line leading to the rear of the turbo control actuator will be similar but with vacuum. Any abnormal response here means you should replace the turbo control solenoids.

Dave

 

Actually I am having a similar problem with my car. However, my car boosts up to 10 most of the time at low RPM's approx 3000. The problem is that I don't have a 10-8-10 pattern. I have all new silicone vacuum lines, replaced both the turbo+wastegate solenoids in front of the UIM. It boosts pretty quickly up to 10-12 then immediately drops down when I shift, then when I floor it again the boost goes to 2 psi and that it, other times it will rise all the way to 10 psi. The only thing I notice is one of the one way check valve sounds like a whistle when the car is running of course. No leaks in the tubong, applied 10psi to check valve holds pressure, but it makes a whistle sound when air is blown out the port. The other check valves do not do this. Could this be a possible problem? I also have an HKS valve controller. When I bought the car the vacuum hoses by the wastegate were capped off, should they have been? I reconnected them, but see no real difference. The valve controller has high and low settings, do not have a clue how to use it. Any comments would be appreciated, hope you solve your problem.

 

I am also having a similar problem and cant figure it out. I get full boost all the way throught the first and start dropping at the second sometimes 7psi but mostly 5 psi and i have checked hose ran solenoid tests and still cant figure out whjat the hell is wrong. I dont have a boost controller and getting pfc soon hoping maybe this will correct the problem and if it does not then im goin non sequential and if that does not work just gonna go to a single. But if anyone has an idea of what my problem may be please pm me or reply to this im tired of the Slownesss.