2nd turbo not kicking in sometimes: help?

[botachi]

Hey guys. (posted this on mkivforums.com in the US as well)

 

Some of you might be familiar with my Supra's on-going problems since I acquired it and made it streetable. But thanks to this board and a bunch of helpful people it's slowly getting ready for regular use! Thanks a lot guys!

 

My last problem now is another intermittent problem. While we were test-driving the car, we noticed that the boost is erratic. Sometimes it will boost only up to 0.3-0.4 bar, and sometimes it will boost all the way to 1.2 bar! When it boost PAST 0.3-0.4 bar you can hear a very distinct swish or noise until it hits 1.2 bar or so, which I assume is from the 2nd of the two sequential turbos kicking in and giving serious boost. And it pulls like a freight train!

 

Assuming that the intermittent boost problem is caused by the 2nd turbo NOT kicking in, what should I look out for? I finally got the WSM for the Supra and have given it to my mechanics to sort out the vacuum lines and hoses. They are checking for leaks and for wrong vacuum line placments.

 

But perhaps this is a problem encountered in the past by other forum members and their experience in trouble-shooting can help minimize the time for me to sort things out?

 

Thanks guys, I hope someone can help me out here again.

Edited July 7, 2008 by botachi
more specific facts (see edit history)

[miko_supra]

tired old vsv's?...seems to be a common issue with the sequential system...My second turbo refused to kick in whilst in first gear

[123tom123tom]

i have some vsv valves:)