If i go WOT or close to it in 1st gear and shift into 2nd and get right back on the accel, the cast doesn't boost. it pretty much stays at 0psi: doesn't vacuum and doesn't boost. if i let off the accel for a sec and then step on it again, it starts to boost.
when i do normal driving in 1st, shift to 2nd, and then decide to boost in 2nd, it boosts like it should. my boost pattern in 2nd and 3rd seem fine also.

any ideas?
btw, last time I had a hose job was done was around mid-Jan2003 by M2

 

That is exactly the symptoms you'd see with a non-functioning or slow functioning TCA. Check out this site for a bit of troubleshooting help. http://www.autosportracetech.com/RX-...leshooting.htm

 

911GT2,
That's good reading but bad news. So the Tubo Control Actuator huh...? Any solutions that don't require me to buy a brand new turbocharger unit?

 

either the check valves not working or the vacuum tank is leaking.
When you let go the throtle for a split seconds, it creates vacuum, enough to move the TCA when you get back on throtle.

 

Turbo control solenoid (under UIM beside ACV). I had the exact same problem a few months ago.

 

what should I do to check each of them? how do i fix each one, whichever it may be?


What'd you do to fix it? New solenoid rack?

 

^

 

Your discription of the "problem" may not be a problem but just how you drive.
Depending on what rpm you shifted at from 1st to second, if the shift point is above 3k from 1st to 2nd. You will not get any boost until after 5.5k. It only does this from 1st to 2nd gear.
So from your discription, not knowing what your shift point is (you can be wot but shift at 4k from 1st to 2nd, you will get no boost until after almost 6k). If you shift it into 2nd and go to redline and still get no boost, then there is a problem.

 

Hmmm I never knew that. If I'm messing around, which i usually am when i'm on WOT, i usually shift into 2nd between 4.5k and 5k.

Can anyone else verify that what Trexthe3rd said is true?

 

No it is not on the rack it is kind of behind the precontrol and wastegate solenoids.

 

The TCA is not actually part of the turbos. It's a seperate unit. But you'll have to test yours first to find out if the TCA itself is the problem or if the problem is one of the solenoids that controls it. Thats what reza was suggesting. The check valves and vacuum tank are what control the TCA. If either the check valves, the turbo control solenoid, or the vacuum tank have an issue, it will show itself as a malfunctioning TCA.

Get yourself a vacuum hand pump (similar to the ones on www.mityvac.com). I got mine from sears for like $20. Go through the testing procedure on the site I gave you above for the TCA, to make sure it's functioning correctly. If it is, then start checking the check valves, and the pressure tank. If those all check out, take of the UIM and test the turbo control solenoid for resistance, the specs are somewhere on this site.

If it is your TCA thats faulty, I have a functioning one from my car that I'll sell you. Good luck.

 

another source of low/inconsistent boost could be a clogged cat.

 

My car is in the shop right now. I'll ask them to check it out for me. Just curious, how much does a TCA usually go for?

 

Is this true?

 

What about cheap (soft) silicon lines running into and out of the vac box? Can't they expand and bubble up and disrupt correct airflow through them, which would cause these symptoms?

Raj

 

I don't know if it's true (RTFM) but my car does it too. I've always suspected a sticky vacuum valve or one way valve, but it's always done it.

If you were "bubbeling up" silicone lines you would have a real problem. We're only talking of a few PSI here. They'd have to be thinner than party balloons. It's possible to collapse vacuum lines, but again, they'd have to be pretty thin walled. I would suspect the actuator would work before they fully collapsed. They may slowly over days/weeks collapse a little at a time and set due to the heat, eventually closing off all the way. That, however, would result in "no-opp" - a permenant condition of no or poor boost.

My lines are original, so they are probably rock hard and uncollapseable, and as I said above, my car has always done it. And yes, I'm afraid to go in there and touch them as I'm sure I'll loose a few solonoids to breakage @ $100 a pop.

 

So what would be the actual cost of these solenoids? My FD is having the exact same problem.