Vacuum leak....at wits end....
 

My car has not been drivable for a few months now due to a vacuum leak that I just cant fix... I've worked my hands raw working on this car, to no avail. It all started when I took the UIM off to paint it. When I put everything back together, it wouldnt idle. It even makes a high-pitched squealing sound at higher rpms when revved. Im 99% sure that it is somewhere under the UIM, because when I spray carb cleaner under it, it smooth out. Ive had the entire intake system off many times before, so I am very familar with it, which makes me even more confused as to where the leak is. I've taken the manifolds off at least 10 times since this has started, looking for things loose or broken, or anything that could have caused the leak. I even bought an entire new intake (UIM, LIM, Plenum..) just because I couldnt think of anything else, and still I have a leak. Im at about the breaking point now...I feel like Im just going to have a breakdown... I've been working on cars and rebuilding engines since before I could even drive, and this is really pissing me off. I have no clue as to what the problem is. Ive been contemplating a LT1 swap for a long time now, and this is just one more thing that may push me off the edge.. If anyone were to have any clue as to what I could be missing, please help me out.. Im all out of ideas, and beginning to run out of will to even care anymore..

not to sound dumb but did you get new gaskets for the intake?

Yes, got new gaskets for everything..LIM to engine, UIM to LIM, UIM to plenum, BAC gasket, the whole deal. Im so frustrated about this right now its beyond words....

Only when you spray under the upper intake manifold? I'm assuming it idled well before hand? What kind of sealant are you using on the gaskets? Did you check for any cracked vac lines/etc. Did you do anything else at all after you removed it? Did you remember the brake booster line? :)

I can't believe you bought a new Intake. Thats hardcore.

Your Fuel Injector's, did you replace the Upper/Lower Grommets and O-Rings. I'm noting your air leak but you never know, considering your certainty of covering everything else there.

It'd be interesting that those started leaking only after removing the intake, but those are a nasty source of vac leaks (my tII suffered that problem), took forever to figure out wtf was up!

I want to add one more thing to this. The car seems to run very well above about 3000rpms, perfectly smooth. This baffles the hell out of me too. This has seriously messed up. We've taken this off numerous times, new gaskets, proper torque specs, checked all vac lines for cracks, EVERYTHING. It's so hard to even pinpoint the squeal it makes, but to me, it sounds like it's coming from the TB. That's about the only thing he hasnt' replaced yet. But it ran fine before he took the IM off. He didn't mess with any of the screws on the TB, or anywhere for that matter when he took it off. Tookit off, put it back on, and this is what happened. It doesn't make sense to me, because there was no alteration in any way to the compoments, but yet, someting HAD to change for this to happen. It's not even my car and it pisses me off. :mad:

injector o rings! Replace them!

Brake booster line..Ill check on that. About the injectors, no I didnt replace the O-rings, but i can like spray carb cleaner directly on them and it does nothing, so Im doubting thats the source of the leak... Im a little calmed down now, so Im going to go play with it some more, Ill keep you posted. Please if you have any more ideas let me know..

Ok, I have a question about the injectors. I have a vacuum leak that I can't find. How would the injector o-rings and grommets cause a vacuum leak? I may have the same problem!!

Do you still have emissions stuff on your car:

ACV and EGR could be a source of vacuum leaks if the diaphragms are shot (easy to check though with a mityvac)

Hugues -

Yes I have all emissions. I will check those out, thanks.. But I dont think that even if the diaphragms were shot that spraying carb cleaner on them would do anything, because they are still sealed internally...

i'm gonna go with injector o-rings and grommets. i helped my friend put in a new engine in his 89 GXL had a massive air leak. couldn't find it. it was just the injector grommets the whole time. lesson learned

well, the EGR stuff is under the UIM so you wouldn't be able to see those lines...

1. I like the loose brake booster hose.
2. To eliminate solenoid vac leaks...cap the lowest of the three metal nipples on the front of the throttle body. Thats the only one that pulls vacuum.
3. Cap both of the small metal nipples on the back of the throttle body.
4. Pull the hose off b/t the acv and the air pump. Cap the hose leading to the acv. Let the airpump just blow into the wind. Not a big deal.
5. Below the water thermo device at the right rear of the throttle body.....cap both hose going to this device. The hoses. Also about a foot below this water thermo device there are some vac nipples. Some are capped. Make sure all are capped. The metal nipple part is what I mean.
6. Heck. Pull the hose off that leads to the brake booster. Cap the hose coming from the intake manifold that feeds the brake booster. Don't drive the car until undone.

7. The engine swap might be a fun thing to do.

8. EDIT: I think there is a vac hose below the air temp sensor on the dynamic chamber and right now I forget where that thing goes to. Cap it off at the metal nipple.

Hey HAILERS, What is your opinion on the injector o-rings and grommets?

Well, I just purchased my grommets from mazdatrix. Cost me $9.28+shipping. I hope it solves my problem, because I have a vacuum leak I can't find.

Let us know how that goes....

The o'rings won't cause a vacuum leak but the grommets will. That's a good move replacing them. Only problem with that is that you've really, really been trying to find the leak and I thought you would have noticed a really bad grommet. The new ones should and will be soft compared to the used ones. Could be one of the old ones has cracked and is causing the vac leak.

Re: Vacuum leak....at wits end....
 

I think you are closer than you realize.
The only two things there are the EGR (diaphragm or vac hose) & the primary injector grommets.

My grommets will be here tommorrow and I will put them on Sat. I will post and hope this solves my problem. I never knew that grommets would cause a vacuum leak. I know now!!!!

Well After 2 more days of not being able to find it, and taking the manifolds off a few more times, I think im going to order all new injector grommets and gaskets and try 1 more time. I'll keep you posted on what happens. I havent drivin my car in months, this sucks...

Weeeeeeee! ;) We'll fix it....with a V-8. :p:

Yea, that LT1 is looking better and better. 275HP and 325ft-lbs..... stock.. I'll take 2...:p: I still need to get this up and running 1st though...one thing at a time..