vacuum leak or something (w/vid)

[7"exhaust_tip]

I have changed every vacuum line that I know of including: the entire egr system and even the brake booster line.

You can see in the video by watching the boost gauge that it is holding vacuum right, but then it like snaps back.
I've run out of ideas and dont know wtf is wrong.

Here is the vid.

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[turbosax2]

Do you notice any problems while driving the car or at idle? It kinda looks like the gauge is messed up....

 

[7"exhaust_tip]

Every now and then it studders a little bit when my boost gauge is on the 0 while accelerating. Other than that, thats about it.

 

[7"exhaust_tip]

No one else has any ideas?

I'm going to try and see if i can test out another gauge to try and eliminate that.

 

[oldman]

Don't bump your thread again.

1. How did you check your vacuum hoses?

2. Have you double checked with a known good gauge?

3. Have you check for kinks on the line going to the gauge?

 

[7"exhaust_tip]

Don't bump your thread again.

1. How did you check your vacuum hoses?

2. Have you double checked with a known good gauge?

3. Have you check for kinks on the line going to the gauge?

1. I replaced all of them and zip tied or clamped them down.

2. not yet

3. Yes, none were found.

 

[oldman]

1. I replaced all of them and zip tied or clamped them down.

The only way to find leaks is to perform a boost leak test, vacuum lines aren't the only thing that can leak.

 

[7"exhaust_tip]

I eliminated all of the boost leaks from the turbo to the throttle body, but am not sure what else can leak.

My throttle body was just rebuilt also, so i know its not the shaft seals.

 

[turbosax2]

I eliminated all of the boost leaks from the turbo to the throttle body, but am not sure what else can leak.

My throttle body was just rebuilt also, so i know its not the shaft seals.

Check your injector seals.

 

[romeen]

I eliminated all of the boost leaks from the turbo to the throttle body, but am not sure what else can leak.

My throttle body was just rebuilt also, so i know its not the shaft seals.

Does this mean you actually pressurized your intake to check for leaks? Replacing all the vacuum lines and EGR is fine but as oldman mentioned the only way to know for sure is to do an actual boost leak test. You can leak anywhere from the turbo to the cylinder head (eg-injector seals as turbosax2 mentioned).

If you have a repair manual it should have a vacuum troubleshooting guide. In Chilton's it's page 3-105 and mentions a valve problem as one possible cause. Do a compression test. Even if doesn't identify the problem you can at least rule out some possible causes.

 

[ricktb]

to me it looks like it could be a sticky boost gauge... like when it snaps from 20hg to 15hg or so. My gauge goes to 22hg when the engine is revving down and tapers off to about 18hg at an even idle. It should be a smooth transition I believe. There is a vacumn tester you can buy at a part store... kinda like the opposite of a compression tester.

 

[Artago]

I think because it snaps like that there is reason to believe that the ISC may be opening on you. Just a thought but I would check the ISC. If you have a repair manual (which you should) it goes over how to test the ISC with an OHM meter. Check the Resistance across pins
1-2 & 4-5
2-3 & 4-5
2-3 & 5-6
1-2 & 5-6
on the ISC. They should show around 30 OHMs. Just my $0.02. Good luck. Tom.

 

[7"exhaust_tip]

Almost a year later, I just thought that I'd update this thread incase someone was searching and trying to research probable vacuum leak causes, etc.

ricktb was correct in his assumption.

Turns out the autometer gauge's vacuum side was sticking and is inaccurate. Boost side was fine.

I installed an new gauge, and thats how I figured out. Vacuum is like 19inHG now.

 

[DroopYeyeS]

I have this same vacuum issue on my '91. The only thing different is that the gauge in question is the stocker in dash. It holds a solid 7psi vacuum. Although it sounds like your issue was aftermarket gauge related.

 

[EclipseTical]

I have this same vacuum issue on my '91. The only thing different is that the gauge in question is the stocker in dash. It holds a solid 7psi vacuum. Although it sounds like your issue was aftermarket gauge related.

forget about that pos in-dash stock gauge and get an aftermarket boost gauge.