gshaffer

I have been working on my '93 (stock except for downpipe) for a while trying to diagnose my 10-5-5 boost pattern. I'm not sure if I'm even getting any secondary boost. Tonight I teed into the Charge Control Actuator. On the side facing the firewall (with the short hose into the Y-Pipe) I got 10-8-10!!??!!. I've never seen that on my gauge. On the side opposite the firewall (with the long hose into the LIM) I got 10in.Hg of Vacuum which climbed slowly to 14 and got to 16 after revving it a couple of times. I took it for a drive and it stayed at 16in.Hg even above 4500 RPM. I did a search and found a suggestion that it could be the hose between the Y-pipe and the LIM that goes into the Y-pipe behind where the CRV goes in. I pulled this off and it was split but when I replaced it I had the same boost pattern. I think I split it when I pulled it off. HELP.....if anyone has any suggestions please let me know. I really want to solve this problem and I am close.

I also teed into the CRV. It had 14in.Hg of vacuum then dropped to 0 at 4500 RPM. I didn't really get on it though, maybe I should try that again with some WOT over 4500 RPM.

Let me know what you all think!

gshaffer

Two other things. When I shut the car down the CRV still showed vacuum and hissed when I disconnected the hose. When I shut the car down the CCA went immediately to 0 Vacuum and the acuator pushed back out. Of course no hiss when pulling the hose.

gshaffer

Good news and bad news:

I found 2 hoses that go from the rat's nest to the UIM between the firewall and the UIM. A cloth-covered one that was disconnected at the UIM and one with a check valve that was stretched out and cocked at the nipple. I replaced both of these hoses. The CCA and CRV now show both vac<4500 RPM & boost>4500 RPM like they are supposed to(the CCA still sucks back in when I shut the car down though). I couldn't wait to take it out and give it hell, but when I did, same old 10-5-5..............****

Now that the CRV is working, any other ideas?

911GT2

Have you taken a look at the Turbo Control Actuator? Maybe checking the CCA and CRV verifies that this works, but anyway controls the prespool of the secondary, and I've heard 5psi @ 4500+ attributed to a faulty TCA, or one of the check valves that goes to it.
I have a similar problem, my pattern is 10-7-7, but as soon as I shift I can't get anything higher that 3psi on the secondary. Anyone else?

Heath

iTrader: (11)

I have a turbo control actuator as well if you need one

damian

iTrader: (2)

look for a leak in the big intercooler hoses, or the big intake pipes

BoOsTin FD

this might be dumb question but what's TCA?
I to have secondary boost loss and i was told to check that but i don't know what it is or where it's at. IF someone tells me what does TCA stand for than maybe i'll figure it out.

Thanks

radkins

Turbo Control Actuator

VTAOE

I had a problem with my second turbo not coming online properly about a year ago. If I were you I would check each of the green and white check valves. You should be able to easily blow through them (in only one direction). If you have trouble blowing through them then they are no good. I made the mistake of thinking that since I could blow through mine (after blowing hard) that they were okay. That is not the case. Also check to make sure they are going in the correct direction. I think that one of mine was on backwards.

The other thing you may want to do is check the solenoids down in the rats nest to make sure that they are functioning properly at the voltage specified in the Manual. The combination of switching out a check valve or two and replacing one solenoid fixed my problem. I then tweaked my boost pattern using pills (Holley Injectors). Hope that helps.

- Cody

gshaffer

All but one check valve is new and that one is ok. I need to pull the UIM and do a hose job as well as check the solenoids. Unfortunately it is my daily driver for awhile and I won't be able to do so immediately. I know there no leaks in the big hoses. I will check the TCA next. Thanks for the advice so far guys.

SleepR1

Check the vacuum chamber and see if it's hold a vacuum. Try the key on/key off sequence. The rod CCA and TCA rods should pull in/out when you key on/key off. Apparently there should be enough vacuum to do this sequence six times.