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Unused vacuum fitting, 2000 XJ

R

rumblebelly

NAXJA Forum User
Location
FT COLLINS, CO
I recently bought a 2000 Classic and I noticed a hissing sound coming from the intake manifold. Looking closer I saw a vacuum fitting without a hose attached. It's located under the throttle body and is the front most fitting of three fittings. I also noticed a vacuum diagram under the hood that confirmed it's not being used.

Just thought it was weird. It seems to suck a lot of air (engine almost died when I put my finger over it) which makes me a little concerned...well, actually more curious than anything. Does anyone have some insight? Thanks!

Greg
 
That's an emissions line that's missing. Check the EVAp canisitor Purge solinoid, lower vacume line. EVAP solinoid is 0n the passenger side near the fire wall. (follow the A/C lines) It's a plastic part with one electrical connector and 2 vaccume lines. (connector is green). It sends excess fuel vapors to the intake when the engine is in closed loop operation.
HTH
 
The reason it almost died is actually pretty simple. There is a little stepper motor that controls what amounts to an air leak into the intake to set the idle speed instead of moving the butterfly like in the old carb days. It adjusts at startup. It had compensated for the air leak, and when you abruptly shut off the leak by putting your finger over the hole, it hadn't had time to adjust to the new setting. If you plug it and then start the engine, it will go through a process of "learning" the new settings and should settle down.
 
No, IMO you should plug it. If you're not going to reconnect the vapor recirculation system then at least plug it. As old_man said the idle stepper motor will relearn when you next run the engine. But a vaccum leak is not a good thing to have, you're loosing performance and MPGs.
 
Why would anyone take it off? Two weeks ago I had the dealer do recall work on it (Recall # 8591 reprogram P.C.M. and Recall # B06 Intake manifold debris shield).

Do you think they removed it for that and forgot to put it on? I never noticed this hissing from the vaccum fitting before while it was running.
 
rumblebelly said:
Why would anyone take it off? Two weeks ago I had the dealer do recall work on it (Recall # 8591 reprogram P.C.M. and Recall # B06 Intake manifold debris shield).

Do you think they removed it for that and forgot to put it on? I never noticed this hissing from the vaccum fitting before while it was running.
Click to expand...

yes it happens... take it back to them if you can.

in the mean time, dont leave it open if you cant find the hose that is supposed to go there then plug the opening.
 
So is it a plug they must have removed instead of a line? It does state on the diagram under the hood that the fitting is "not used" without any vacuum lines going to it. It came from Illinois if that makes a difference.

It runs fine, even has okay mpg which is weird. I'll plug it and take it to the dealer tomorrow. Thanks for all your help.

Greg
 
I covered the fitting last night. I didn't seem to run much different but there was a hell of a lot more air getting sucked through the air intake. Maybe it idled slitghtly smoother...could all be in my head though.

I went to the dealer this morning and we found a cap that was supposed to cover the fitting laying behind the air cleaner on the fender well(?). He said it's just an accessory fitting that wasn't being used. There's already a hose going to the evap canister and I couldn't find anything another hose could have attached to anyway. We're not sure how it came off...or when. Is it possible I could have hurt something?
 
DaffyXJ said:
That's an emissions line that's missing. Check the EVAp canisitor Purge solinoid, lower vacume line. EVAP solinoid is 0n the passenger side near the fire wall. (follow the A/C lines) It's a plastic part with one electrical connector and 2 vaccume lines. (connector is green). It sends excess fuel vapors to the intake when the engine is in closed loop operation.
HTH
Click to expand...

I have a question about the closed loop mode. Is it normal for the intake to be sucking a lot of air in this mode? When she warms up, the air intake drops tremendously.
 
The mechanic probably had it hooked up to a vac gauge during the reprogramming and just forgot to take the hose off and put the plug back on.
I had my shocks replaced once and the dealer mech put the rubber donuts from the old shocks on the intake manifold and left them there. Hit a bump and about 1 min later in traffic I could smell this burning rubber smell. It was me :D
Got to work and popped the hood to find one of the donuts resting and melted against one of the exhaust manifold flanges...
 
rumblebelly said:
I covered the fitting last night. I didn't seem to run much different but there was a hell of a lot more air getting sucked through the air intake. Maybe it idled slitghtly smoother...could all be in my head though.

I went to the dealer this morning and we found a cap that was supposed to cover the fitting laying behind the air cleaner on the fender well(?). He said it's just an accessory fitting that wasn't being used. There's already a hose going to the evap canister and I couldn't find anything another hose could have attached to anyway. We're not sure how it came off...or when. Is it possible I could have hurt something?
Click to expand...
 
I found the same connection on my 2000xj intake manifold. Sticker said that it is not used like yours. Concerned about drawing unfiltered air into the engine i took a short piece of hose and plugged it with a bolt and capped the connection with that. The result I got was 300 rpm slower idle, noise coming out of my tail pipe is quieter, My engine is harder to start, and with the connection plugged I now notice a slight hissing noise that I do not hear when it is not capped. I don't know if this changed mpg as I just capped it yesterday. Engine seems to run fine other than starting harder.
 
Would this unused connection be a good place to attach a vacume gauge to mount on the dashboard? Or what kind of accessory would be be attached here?
 
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