Where are the vacuum leaks?

O

OneBadTT

Member
Joined
Dec 29, 2004
Can someone help me find my vacuum leak? A list of where to look for the common leaks would help. My RPMs continue to run high in park- 1500 RPMs and in drive without moving- 1200 RPMs. I have replaced most of the vacuum hoses that I see but I still can't get the RPMs to drop. Tried the IAC and TPS adjustments with no luck. It's driving me crazy! :eek:
 
What are your IAC counts at idle? Have you tried turning the throttle screw out and resetting the TPS?
 
yea re-check your IAC and TPS numbers and still no luck double check your lines, have you checked the vacuum ball underneath the driver side head lights or the A/C control lines behind the dash and glove box?
 
OneBadTT said:
Can someone help me find my vacuum leak? A list of where to look for the common leaks would help. My RPMs continue to run high in park- 1500 RPMs and in drive without moving- 1200 RPMs. I have replaced most of the vacuum hoses that I see but I still can't get the RPMs to drop. Tried the IAC and TPS adjustments with no luck. It's driving me crazy! :eek:
Click to expand...

I went through the same thing. Visit this thread and see if it will help your cause. http://www.turbobuick.com/forums/scan-tool-tech/311284-frustrated-scanmaster-readings.html
 
I've found leaks at the EGR valve and the plastic vaccum distribution block on the throttle body. Replaced the EGR valve with a home made bock off plate, and the plastic block with a billet aluminum piece.
 
Thanks everybody.

discostu- I have made a lot of adjustments but can never seem to get the TPS and the IAC at the right numbers. In fact, I can't get the IAC to go above zero not matter what I do!

LS954- It's funny you mentioned the vacuum ball by the headlights. I traced the vacuum line to the ball 2 days ago- that was the first time I ever noticed it. I couldn't find any leak there, but I am going to check again. I haven't checked the A/C control lines behind the dash and glove box- I never knew there were vacuum lines there. I'll check that tomorrow.

Chuck Leeper- I did check the EGR valve and I changed the vacuum hose on it a a couple of weeks ago. Would it leak from anywhere in the egr valve other than the vacuum hose?

Dreamcar86- Thanks for the link. I'm going to read it and see if I pick up something that I have missed.

Speed Dreamin'- Was the EGR leak at the hose or inside the valve? I think I'm going to replace the vacuum block with a billet one. How about the metal vacuum hoses on the passenger's side going into the block- do they ever get leaks?

I really appreciate everyone's help. Please keep those ideas coming!!
 
Dreamcar86- great link! I'll try some of the stuff from the link. My BLMs run from 115-119 at idle. FP stays steady, but I had a hard time ID'ing whether the boost and FP went up together under acceleration. I guess I'll work on that more after I get the vacuum leak fixed.
 
Saw a thread about EGR leak...
Seems it was leaking around the stem/body.
Also, if the diaphram is ruptured, it will leak.
QUICKY TEST:Remove the hose, push the diaphram up, put your finger over the hose barb, let go of the diaphram. Does it hold vac?
If not, it's toast.
Or, use a vac pump, [I use a hand held unit], pull a vac on it. Does it hold?
Have you taken the valve off and cleaned the port and the valve??
 
Yeah Chuck that was me...My EGR lleaked around the stem on the intake side not diaphram side.

Best bet is to pull the rocker shafts and then psi the compressor inlet to 30 psi and tehn spray soap/water soloution over everything and youll be surprised.

Leak tester can be bought here

http://www.siliconeintakes.com/index.php?cPath=8&osCsid=f77f11300eb292f1aaa78d728ece11c9

I found 3 ports leaking on intake gasket
All the ports on my alum vac block leaking
Egr stem
One IC pipe conection would hold till 18 psi then leak and reseal around 16ish psi

So its worth ethe time to pull the VC and rockers Cant truly rule it out until done.

I tried Propane, carb cleaner, brake cleaner, wd40, ether and the engine NEVER change idle FWIW.
Do a search under my name and youll find the old thread
 
I did the finger test on the EGR and it held the pressure until I moved my finger away from the barb. It held real good pressure. I also took the valve off and cleaned it but no luck.
 
Interesting thing- I backed off the IAC screw a couple quarter turns last week. The TPS went down as expected. I had it set to 46 and now it's sitting on 42. The interesting thing is that I noticed the last 2 days is that the IAC on the scanmaster is showing about 56 when I start the car. Then when I drive it around the block a couple of times, it drops back to zero.
 
Years ago (I'm guessing 7 or 8 yrs!), someone here had a procedure for smoke-testing the entire intake/engine/exhaust tract. Not even sure how you'd search for that or if it's still here...
 
S10xGN said:
Years ago (I'm guessing 7 or 8 yrs!), someone here had a procedure for smoke-testing the entire intake/engine/exhaust tract. Not even sure how you'd search for that or if it's still here...
Click to expand...
My mechanic hooked up his smoke machine to a vacuum line and found leaks I would never have found. Some people here thought I was kind of wimpy (or had too much money in my pocket to spend) but I think it was worth it.
 
i rigged up a regulater and put about 10psi through the turbo and listend for leaks it may not leak at vacuum but when you trasition to boost there could be leaks
 
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