Weirdest vacuum leak I've ever had

[thearkatek]

I bought my 92 Talon AWD a few months ago and I've been since tracking down all sorts of problems. But my vacuum leak problem is the strangest of all.

My car idles at 1500 and the vacuum on my guage says around 10 inches. I've found a lot of vacuum leaks and fixed them (like a chunk missing out of my intake manifold gasket) but it didn't change my idle. I used the FIAV blocking plate. But have since had to disconnect my idle switch so my car doesn't go crazy at idle. The ISC coils all read around 30 ohms, and when I turn on my car it sucks the actuator thing all the way back in. I'm assuming that's correct operation.

So I did a boost leak test. Found my leaks, and fixed them all except a tiny hiss through the throttle shaft. I did a compression test and all cylinders read around 175psi. I've sprayed tons of TB Cleaner around listening for a change in idle, but none! uggg this is such a pain in the ass.

My next step is replacing the throttle body or replacing the gasket. The only thing I can think of is maybe the leak is in such a way that when under a vacuum it leaks more than under positive pressure. I also noticed that when I pump the breaks really fast the idle raises... but I think that's normal.

Right now I have my ISC, FIAV, and idle switch disconnected. I just use the BISS screw to set it.

Thoughts?

 

[ChiTownHussla]

check brake booster hose for vacuum leaks?

 

[thearkatek]

Ya I'm going to pinch the hose off today after work. When I did the boost leak test i didn't hear it hissing over there though.

 

[Calan]

Please fill out your vehicle profile.

 

[slayer450]

Throttle body shaft seals are shot, very common leak. Cheap and easy fix

 

[thearkatek]

Please fill out your vehicle profile.

Will do.

And the thing is I didn't think the TINY hiss the throttle shaft is making would cause almost 10 inches of vacuum loss at idle, but I am definitely going to replace the tb asap.

 

[Calan]

... but I am definitely going to replace the tb asap.

You don't have to replace the entire TB... just the shaft seals.

 

[thearkatek]

True. And really the one in the junk yard I was gonna grab is probably leaky too . Ok gonna find a shaft rebuild kit.

I guess the weirdest thing is that when I first did a boost leak test it wouldn't hold pressure for more than half a second. This was because the intake manifold was absolute junk. After replacing that I didn't notice any real difference on the boost gauge even though it holds pressure for a long time now. But I guess before anything I just need to get rid of that little hiss from the throttle body shaft, then go from there.

 

[crash89]

Just be careful when taking the throttle plate out. The two screws can be a pain in the ass. I almost stripped mine out trying to take them out the first time.

 

[Calan]

I would just count on replacing the throttle plate screws. Once you get the old ones out, replace them with new screws and red Loctite.

Contact Brian (snowborder714) on here for TB rebuild parts.

 

[thearkatek]

Ya I can imagine. Hopefully they are made out of harder metal than those butter screws that were holding my lower throttle body assembly on. Thank god for vicegrips.

 

[toppertopper]

Ya I can imagine. Hopefully they are made out of harder metal than those butter screws that were holding my lower throttle body assembly on. Thank god for vicegrips.

They are worse then butter screws , i just had the same leak , replaced the seals and no more leaks

 

[thearkatek]

There is hope! haha ok gotta get those o-rings.

 

[thearkatek]

The brake hose indeed does not have a leak. Today after work I'm going to try to find the proper o-rings and replace the seals.

 

[BoostedBeaver]

If you must replace the brake booster hose, just remeber that there is a one way check valve built into the hose.

Robert

 

[thearkatek]

Thanks Robert. Ya I found that out last time I changed it in my tiburon haha. But ya I replaced the seals in the TB shaft tonight. The old seals crumbled out... So it idle's a lot better but it's still pulling a low vacuum. Going to replace the gasket on the tb tomorrow because it's ripped. I put a bunch of gasket maker on it but that might not have done it.