Recently Bought DSM..No Boost...3-4k idle..just a couple search follow up questions

[jarredsyxx]

http://www.dsmtuners.com/forums/showthread.php?t=91439&highlight=intercooler+pipes

...Let me tell you a bit of the story, I just recently bought a 1991 Eagle Talon Tsi (FWD)...From a kid who was going to use it as a project car...I got it at what I believe was a fair price...but heres what the main problem is... the idle is awful...it can go as high as 4k...stays in the 3.5k range...then its like ...maybe pressure builds up ...and it goes down to 2.5k ...its not a surging idle...I searched and learned all about that...as soon as you start the car its up in that range

now ...while driving the car...I did notice that even on the stock boost gauge, yes they are very inaccurate, but they do display if you have something there... the needle stayed on the negative side (vac)...thru alot of the driving...sometimes...occasionally it did jump into the boost side...I did hear the turbo spool...and it sounded nice...

To make a long story short...the thread above is the only thread I found that sounds like my problem...this car is untouched basically....which is a good thing...but what Im wondering ...is if my intercooler piping ...being shoddy and in some places showing signs of dry rot...is the problem for my lack of boost and terrible idle... after reading that post I felt that it maybe my first step of diagnosing the problem...but I wanted some feedback because this is my first Turbo car...and Im excited about tackling the problem and learning more as I go...any help or suggestions you would offer would greatly be appreciated...and I am excited to become a member of a great DSM family...

Thank you in advance....

 

[MrBoxx]

During cruising, you're not going to see boost. In fact, when driving around, not on the throttle, most DSM's will see about 18 in/Hg vacuum or less. The only time it's going to be boosting is if you're accelerating or there is some other load on the engine (going up a hill while remaining at a constant speed will actually cause boost to rise). Were you expecting the car to be in positive boost at all times? However, if you notice that the boost gauge isn't moving when you're acclerating quickly, there may be a boost leak. Make a boost leak tester as per the vfaq and test the intake.

Also, while you're doing that, check the turbo for shaft play. Stick your fingers in the compressor housing inlet and try to wiggle the compressor wheel up and down and side to side. A very small amount of movement is okay. Any movement that you can feel, or movement that causes the blades to rub the compressor housing is a sign that you may need to replace the turbo soon. It's just one of those things you should check every once in a while.

 

[jarredsyxx]

thanks for the quick reply...

actually maybe myself I was a victim of lack of knowledge... okay... it does go towards the zero and sometimes a bit over during acceleration...now Im understanding that maybe that doesnt mean I dont have boost...

Im definately gonna pull off the pipes today and check for shaft play... so basically from my understanding...is pull off all the pipes...intercooler and vaccum and check them... can they be the source of super high idling like that? I mean in a naturally aspirated car...where my experience is...I would say oh yeah...

my last question for the day...yes Im sorry...Im reading learning more every day... what factor does vaccum play in boost... if you have a vaccum leak, will you not be able to adequately pressurize the system? If someone even maybe has a link to a technical page with that date I would love it and appreciate it very much... I looked but didnt see anything in the vfaq.com

Thanks again

 

[MrBoxx]

Yes vacuum leaks in the intake system pretty much equal boost leaks and won't allow the system to pressurize as fast (and if the leak is big enough i.e. intercooler hose blown off, it won't pressurize at all). Usually, they don't affect idle like the problems you're describing, though.

I'm honestly not very good at diagnosing idle problems, since there are quite a few systems that can affect idle that I'm not familiar enough with, like the throttle position sensor, fast-idle air valve, BISS screw, etc. Hopefully someone more experienced with idle issues can clear up the problem for you soon.

 

[jarredsyxx]

youve been awesome though...I really do appreciate it... your post made me look further... Ive got a new thread started with pics if you wanna kinda see where this goes...

Moderator you can close or delete this thread...started a new post...

thank you again