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Repairing a broken vacuum line to MAP

9

90cherk

NAXJA Forum User
Location
Oregon
While pulling my injectors on my '90 (originals with 220K !) last night for replacement since they have started leaking at the seam ( I finally ordered some Bosch D5B injectors from fiveomotors) I broke the rigid vacuum line from the MAP to the throttle, right at the grommit attaching it to the throttle assy so there is no post left to slip a tube over to couple the two pieces. Anybody have this happen to them? I was thinking of drilling out what's left in the grommit and shoving in the remaining vacuum line with a little help of some RTV. Do you think that'll keep it in place? The "stealer" wants $30 for a new tube assy.
 
Well...

You can "patch" the line with some vacuum hose - I'd apply a little silicone to the ends of the hose to make sure to get a good seal, and pull a zip-tie down good and tight to hold it there.

Also, you might want to check with a local NAPA. I don't recall the part numbers offhand, but you can get most of the vacuum wiring there for about $50 both halves of the harness, and the CCV line.) Why? Just to make sure - if you're losing one line, you're on the edge of losing several...

I haven't seen the MAP line anywhere tho - I end up patching them using rubber vacuum line. I plan on taking the throttle body down and seeing if a threaded fitting can be installed in the throttlebody to allow the use of a full-length bit of hose, but I haven't gotten around to it yet (I need a throttle body I can remove from service for a while...)

5-90
 
Thanks for the suggestions but it broke off at the wall of the grommit so there isn't anything to slip a hose over to splice the pieces. From what I'm finding out there it looks like this is a low pressure line, it just needs to be sealed to run the "heep"
 
It's actually a "negative" pressure line - low vacuum to the MAP sensor. The catch is, you need inputs from the MAP and the IAT (Intake Air Temperaure) sensors to meter fuel, so your fuel mileage might go right to Hell.

Second plan - see if you can find a bit of metal tube that will fit into the grommet, and use that for a stub for the rubber "patch" hose.

Just a thought...

5-90
 
I replaced the injectors, drilled out the broken off stub in the grommit and RTV'd the remaining MAP vaccum line into the grommit. So far, so good, hopefully it doesn't fall out while out on a trail.
 
Nevada City Sparky said:
Anyone thought of using steel fuel or brake lines to replace these? Only issue I could see is smog inspection.....
Click to expand...
I did that when mine broke. Hose wasn't working well for me. I used the smallest brake line I found, bent it to fit and used hose on the ends with small locking plastic clamps from Napa; two zip ties with the loop ends oposing each other would work. I have been told by others to use as little hose as possible due to the fact that rubber hose isn't ridgid enough to maintain the exact vacuum that the MAP is supposed to be reading, especially on hard deceleration or closes throtle when vacuum really rises. When I replaced the engine, I just bought a bunch of new harnesses. The small Jeep dealer I use is very good to me. But, the vacuum line worked well for me- I still have it just in case.
 
try going to a pick and pull or similar junkyard.

try getting all the "little things", it'll save you time and money whenever you need to fix something quick.
 
uvaldetxj said:
try going to a pick and pull or similar junkyard.

try getting all the "little things", it'll save you time and money whenever you need to fix something quick.
Click to expand...

I'd just buy new lines. They are cheap at NAPA and most of the lines in the boneyard have too many years on them and are as brittle as the ones you're replacing. I have gotten lucky and found the grommet from the back of the valve cover looking like it was recently replaced.
 
1987 4.0 AW4

Guess what? I was replacing my injectors and did the same thing. Broke the line as it
entered the grommet, and idles all over the place. I drilled it out and stuck the remaining tube in, but the diameter now is off from the original.

My question: is the grommet included in the NAPA kit? They are closed now.

Thank you!
 
AJPulley said:
I did that when mine broke. Hose wasn't working well for me. I used the smallest brake line I found, bent it to fit and used hose on the ends with small locking plastic clamps from Napa; two zip ties with the loop ends oposing each other would work. I have been told by others to use as little hose as possible due to the fact that rubber hose isn't ridgid enough to maintain the exact vacuum that the MAP is supposed to be reading, especially on hard deceleration or closes throtle when vacuum really rises. When I replaced the engine, I just bought a bunch of new harnesses. The small Jeep dealer I use is very good to me. But, the vacuum line worked well for me- I still have it just in case.
Click to expand...

the brake line definitely makes a more "sanitary" looking attachment if you take your time and bend it right. I would still use a good 4-5 inch piece of hose on the MAP side, though. The throttle body is moving with the engine and the MAP is solidly mounted to the firewall-- you need enough flex in your line to account for the movement.

edit: I just realized that was from 2005-- I'm sure he's either figured it out by now, or been through a butt-ton of MAP sensors...... derp

Greg-- I don't think the MAP line came in my set, but if it did there was no grommet included.
 
Last edited:
As I mentioned above, I broke off the MAP vacuum line at the TB when doing my injectors. Drilled out the hole in the grommet to accept the full tube, RTV'd itin place.

Worked great for 6 weeks. Worked loose today, the joy of stalling at a busy
intersection.

I tested the vacuum "pressure" at the TB, and at another vacuum line: the same. So I got some 1/8" plastic emission line from NAPA, and spliced into
another vacuum line. I stuck the grommet back in the TB, put a small screw in the old vacuum hole, and used black RTV to plug it.

Problem solved. You can use the fitting on the MAP, just pull out the old line and put in the new flexible line and tap into any other vacuum source with an adapter.

Hope this helps someone down the road!
 
Sorry, I'm a little confused.

Why don't you just pull the grommet out of the TB, then pull the line, or force the line out, then shove another hose in there. There are 2 "nipples" on the TB grommet. One is just a keeper, and on the TB it's just a blank hole, the other hole is for the vac line. 1/8th is the right size. You can also use 1/8th" drip sprinkler hose...for about 25 cents a foot.

The blank hole is irrelavant
 
The original tube narrowed, it wasn't 1/8th inch when it went in the TB. I guess I could of used the new tubing in the TB. The old tubing, after it broke,
had a bend that put stress on it after I put it back in the grommet. I think this made it work loose from the grommet.

Hope that makes sense:)
 
ParadiseXJ,

The more I think about you are correct. I could have used the more flexible line in the TB grommet. It wouldn't have been under the stress like when I was using the old pre-bent
piece.

Hey, I am learning so much about this Jeep. Had it since 87 and it wouldn't be running like is now without the help of NAXJA!
 
when i was playing with my injectors on my 90 xj i broke that line too, i just got small rubber hose and clamped it on. Works great!!
 
pretty sure i did the same thing haha, put new injectors in my 90 and noticed that vacuum line looking floppy. weird thing is it ran fine the first time i started it. then started it the other day and it is running really rough and smokes a bit. sound like a busted vacuum line?
 
Did it run fine before you replaced the injectors?
How does "floppy" look? I knew when I broke mine. Get it running a spray some WD-40 around the grommet where the vacuum line enters the TB.
If it is leaking, the RPM's will increase. Unless the new injectors have an issue. It's always fun when when you make a couple of changes and try to
figure out which of the changes didn't work:dunno:
 
when it was idling it was moving alot. ran fine the last time i wheeled it and parked it at home. then the injectors starting leaking really bad so i replaced them. started it up noticed the line moving a lot, noticed it was broken. then next time i ran it it ran awful and smokes, and smells rich. pulled the plug out of the TB and it runs even worse. so i found my problem just gotta get a new vaccum line. after that ill do normal tests if it still runs rough
 
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