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Vacuum line popping out of throttle body

D

Don Becker

NAXJA Forum User
Location
Beaverton, Oregon
I'll start by apologizing for the out-of-focus photo . . . 'best I seemed to be able to do!

This is an 88 XJ, 4.0L. The oval-shaped grommet on the right side of the throttle body into which attaches the vacuum line to the MAP sensor, keeps popping-out of the throttle body. As you can imagine, this causes quite a vacuum leak.

Now, I can glue it back and that's probably okay but I just thought I'd ask if anyone else has experienced this and whether it might be a sign of some other ptoblem.

We own 3 XJ's - - - many, many miles and this has never happened. 'Poke it back in place and it stays for several days. I think I'll just clean the surfaces and glue it on there (yes, I'll be careful not to get the glue where it shouldn't be). I'll probably use a rubber-type cement.

'Any input before I do this? Thanks! Don

http://www.villagephotos.com/viewpubimage.asp?id_=14734540
 
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You are aware that there are two ways it can go in. Compare to your other vehicles to see which way, I have also seen them pop out if the engine backfires.
 
I didn't know that but, I looked at my other '88 and it is oriented the same as I have on this one. And, I sure haven't heard any backfires. The only time this XJ runs badly (lately) is when that grommet falls out. Any other ideas/input? Don
 
It looks like your "blowby" pressure is greater than your intake vaccuum- are there oil stains on your intake filter?

Start checking into your CCV system- the intake and filter tubes from your valve cover. There's a little "orifice plate" on the back of your valve cover, and once that gets plugged up, then all kinds of pressure/vaccuum problems start cropping up. The MAP sensor is supposed to always be under a vaccuum, so blowing that line would definately mean you aren't under a vaccuum anymore.

Search under "blowby", and be prepared to do some learning. Some folks get by with the OE stuff, and others like me just don't care for what was given to us from the factory.
 
A blowby problem will not cause the vacuum line problem. They are two different systems.

To fix the vacuum line without glue, try a piece of heatshrink, shrunk down, over the end. That should make a tight seal.
 
I have no blow-by problem (yet) with this engine. And, the heat-shrink idea won't work . . . we're talking about the oval-shaped grommet that "pokes" (for lack of a better word) (attaches directly to) into the side of the throttle body . . . it isn't the vacuum tube that's fallign out . . . . . 'hope that makes it a little more clear. Don
 
I had a tough time getting mine back in after removing the odd-shaped rubber grommet. Ended up using a screwdriver or small prybar to poke the rubber grommet back in until it stayed in place. I feel your pain.
 
Mine got old and shrank a bit, I put a very thin coat of silicon around the outside of the stoppers (both)(used a very small brush), being careful not to put too much on. I've even had it out since I siliconed it the first time, I just added another very lite coat of silicon. One thing I didn't do, was clean the holes in the TB out with solvent, I'm guessing there was (is) a layer of dirt in there so the silicon didn't glue absolutely solid. A Q-tip with a drop of oil on it, smeared into the holes on the side of the TB, may save some serious aggravation, if you ever have to get it back out again. If it pops off again on it's own (with the coat of oil), you can always clean the stopper and the holes in the TB with solvent and do it again.
 
Check that fittings - there's a bung with the hose, and one with a "blind" bung that is ribbed. Over time, those ribs start to wear loose.

The fix? Take the fitting and apply some RTV black to the upper "blind" bung. Allow it an hour or so to cure before you run anything - this will help to retain the hose.

I ran into this about three years ago. I've only had to reapply the RTV when I remove the throttle body - for a cleaning, and once again for a manifold gasket job. It works quite well.

5-90
 
A trick to soften that rubber plug is to soak it in Clorox for a few minutes.
 
My gosh! You guys ALWAYS come through! Thanks! I think I'll do the RTV thing in the morning. Thanks again! Don :kissyou:
 
Yes it is.
 
One of these days, I plan to dig out that spare RENIX throttle body I've got kicking around and see just how difficult it would be to put a barbed pipe-to-hose fitting in there. Then a small clamp, bit of twisted wire, or a zip-tie will solve the whole damn problem.

Just haven't gotten around to it yet...

5-90
 
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