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Old 11-21-2010, 12:35 PM   #1
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Vacuum port on intake on 2000

Ok, just picked up this 2000 Sport, and going through things making it nice again and I found this vacuum port open on the intake, no plug, no extra lines running anywhere. I have no idea what to do.. Am I missing a line somewhere? just need a plug? TIA


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Old 11-21-2010, 12:39 PM   #2
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That doesn't look right but if it were an open vacuum fitting, your idle rpms would be screaming high.

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Old 11-21-2010, 12:43 PM   #3
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That doesn't look right but if it were an open vacuum fitting, your idle rpms would be screaming high.
I don't experence any idle issues, if anything it's a bit low,(automatic) I tried capping it and it boggs down, thinking it's for an emissions thing.
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Old 11-21-2010, 01:17 PM   #4
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Bet your heater or AC doesn't work right now. Look around, the line that should go on there is laying around someplace close by, probably down underneath.

It may also be part of the purge system - eventually it may set an evap code.

That port is manifold vacuum. It may affect the idle when cold before the computer comes on line, but the PCM will compensate for the extra air and adjust the idle appropriately.
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Old 11-21-2010, 01:24 PM   #5
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That port is manifold vacuum. It may affect the idle when cold before the computer comes on line, but the PCM will compensate for the extra air and adjust the idle appropriately.
Rich, how can the PCM compensate for that extra air and adjust the idle so it's not screaming high when it can't do the same for a leaky intake manifold after someone doesn't reinstall it correctly after installing a new set of headers?
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Old 11-21-2010, 01:48 PM   #6
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Bet your heater or AC doesn't work right now. Look around, the line that should go on there is laying around someplace close by, probably down underneath.

It may also be part of the purge system - eventually it may set an evap code.

That port is manifold vacuum. It may affect the idle when cold before the computer comes on line, but the PCM will compensate for the extra air and adjust the idle appropriately.
Well, I will look around underneath, haven't seen anything before, actually the heater works very good.. ok only on high but it works right.. Not sure if they could be connected? mmm no fan on speeds 1,2,3 only 4 for that I looked at replacing the blower resistor, (used from salvage yard, 4 of them) and a relay but no worky. Don't feel like throwing another $50 not knowing if it is gonna fix it.

I found 2 pic's of that manifold and both have that port capped. so this is driving me nuts, but no descripition of where it goes. BTW no codes at all got those fixed..
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Old 11-21-2010, 01:50 PM   #7
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Good question - that port is small compared to the intake leak when it's caught on the studs. If it was as large as the intake leak it would run too fast. The PCM/O2 sensors would see it's too lean, so it adds fuel, the IAC can't compensate for that much extra air and fuel, it does the best it can, but it only can do so much, resulting in an idle way too fast.

Small manifold leaks like just a sealing problem or the proverbial cracked manifold act the same as that port open. Find them easily with propane.

You have that port on yours, try pulling it off. Idle will change a little, then go back to normal. IAC in action!

I'm not sure - it's been awhile since I looked, but that port may even have an orifice inside, small mirror and flashlight will tell.

It's a good place to attach a vacuum gauge for troubleshooting too (plugged exhaust, valve action, restricted intake, etc.)
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Old 11-21-2010, 02:01 PM   #8
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If you still have th VECI sticker under your hood it will have a vacuum diagram that tells you what is supposed to go there.
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Old 11-21-2010, 02:12 PM   #9
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I just went out and looked - braved the cold 59 degrees.

My '03 has 3 ports there. That front one goes to a rubber line that runs next to the inner fender splash panel, then down, then turns into a steel line that runs down underneath toward the back - probably to the charcoal canister, part of the purge system.

Neither of my 89 and 91 Cherokees have ports there, but that's where the EGR valve is.

The open rubber line probably is flopping around against the splash panel. You could put a cap on the port, but next time the PCM runs the evap test, it probably will set a code. But you'll know why.
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Old 11-21-2010, 04:18 PM   #10
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I looked on my 01 and the front port goes right over to the evap purge valve on the fender well. The line that your arrow is over the top of is what mine is connected to

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