sk8world

iTrader: (5)

ok, I know this is a worn out topic... I have been suffering my first real problem with my Fd in 6years! So I guess I am way over due....

Boost drops to 4-6lbs after 4500 transition in all gears and does not recover. Happened a few weeks ago while doing some spirited street driving. Almost like a host came off. I spent several hours trying to find a bad hose but nothing. So I went ahead and did another complete hose job, this time in silicon! I checked the relief and bypass valves, checked all check valves. Only test I was not sure about was the actuator (charge control) The test shows the rod in while car is running then turn car off and remove vacuum hose and the rod should come out but mine comes out as soon as the car is turned off?? But when I put pressure on one side it closes and vacuum to the other side opens it so I think its good??

I have also checked the vacuum chamber and it is not full of oil and holds pressure just fine. The only thing I did not do is change the vacuum lines going to and from the Actuator (turbo) (the one located under the turbos that is accessiable from under the car. I checked them as best as I could but they felt fine, Not dry feeling. Ran my fingers down them for splits or dry areas but nothing.

The other thing that may be a sign is my vacuum guage reads 11-12 when car is at idle after warm up. Used to be 15-17 area. Can a solenoid be leaking?

Thanks to anyone who might be of some help. Oh, I also went ahead and added a y-pipe today while doing the hose job...

cruiser

Hmm, only time I had a 11 reading on vacuum gauge was when my MAP sensor disconnected. Its strange that you get 11 vacuum and full boost on primary - I would expect to have normal vacuum reading if only the secondary turbo boost was a probem.
I had similar problem yesterday and found a disconnected hose from the pressure chamber. Not much help I suppose

SleepR1

The CCA is probably fine. Everyone else's CCA rod pulls out when the motor is shut off.

What does your primary turbo boost read on the boost gauge BEFORE transition to twin turbo operation?

@ idle, in neutral, depress the gas pedal WOT to redline. The boost gauge should jump to 4 psi. If it does not, you have boost leak somewhere in the system. Start with the turbos themselves, and work out to the intake manifold.

sk8world

iTrader: (5)

thanks, tried the wot in neutral and get 3-4 psi? will have to test drive to see the transition again but I believe yesterday it was pulling 12 lbs before transition then dropped to 4-6 and stayed in that area.

SleepR1

This is good, at least you don't have a boost leak to trace. It's a matter of a secondary turbo being bad or not coming on. Check the shaft play on the second turbo. Remove the intake elbow pipe attached to the second turbo, and you'll see if the second turbo is bad...

SERIES7

Check your stock duty selenoid. Or just try the home-depot MBC mod to see if in fact it is that.

sk8world

iTrader: (5)

??? CAn you be more detailed, I am not familar with this. Thanks, Mike


Check your stock duty selenoid. Or just try the home-depot MBC mod to see if in fact it is that.

Sleepr1, I did check the second turbo, (even though not sure what I am looking for) There was a little shaft play? But other than that it looked fine. ?

SleepR1

There should be a little, but not too much so that the shaft is "wobbling" within the housing...

sk8world

iTrader: (5)

well it was just a small amount. not wobbling be any means.. Can there be an acttual leak from the turbos themselves? I mean with 11-12 on the vacuum guage makes me think there is a major leak??

SleepR1

11-12 inches Hg vacuum is not unusually low with a modded FD and street ported motor when idling in neutral. Vacuum leak will be tough to find. Good luck!

sk8world

iTrader: (5)

Thanks for the help.

Well it not so much that is low over all but before the turbo problem it was more like 15-17 HG.

Anyother ideas from anyone?

sk8world

iTrader: (5)

???? More details on this please!

Check your stock duty selenoid. Or just try the home-depot MBC mod to see if in fact it is that.

Mahjik

iTrader: (1)

Seems odd, but have you checked your UIM gaskets? When was the last time you replaced them?

Dropping down to 11-12 on vaccum it's a pretty good leak you've got somewhere. I've seen missing/blown UIM gaskets cause some fairly good leaks as well as unstable idles.

zyounker

Very odd.. my friend just picked up a 3rd gen last week with this EXACT
problem.


Here are his symptons

Low vacuum 10-12HG
full boost in 1st gear
after the transition it drops to like 4psi


Now here is what is odd:
rebuilt engine & turbos


I thought the engine was probably toast because of the low vacuum.. but i
really doubt the turbos are screwed..


I was gonna do a non-seq mod to his and see if i could get the 2nd turbo
to boost just to test it.


Anyway, just posting on here, to keep an eye on the thread.


-Zach

johnisenglish

Bringing this post back from the dead!

I'm having the exact same problem right now, and while I'm planning on doing the hose job next week, I'd like to know if either of you guys were ever able to nail down what the cause of the lack of secondary boost was? Right now I'm leaning towards the pressure system going to the turbo control actuator...

whiteshadow

I don't know if it will help or not, but I recently assembled a bunch of notes about what each of the components do and what (theoretically) happens when they fail. I was having a similar problem, but only getting about 3 PSI after transition. Turned out I had an intermittently bad turbo control solenoid (vacuum) so my turbo control actuator wasn't opening.

http://www.millsisland.net/twiki/bin...ntDescriptions

It could be related to a leaky solenoid or lack of vacuum, although it doesn't sound like it. Have you hooked up a mitivac to the system yet and see if it holds vacuum? The easiest spot is the hose coming off the vacuum tank. Just suck it down with a vacuum pump. It should hold 20 in vacuum steady for hours. If not, you've got a leak somewhere.

If you've got a spare boost gauge, hook it up to some of the monitor points that I suggest on the page. Drive around and see what happens. Otherwise, just re-hookup your daily boost gauge to whatever you want to monitor.

Good luck. Turbo diagnosis is a pain.

Rich