I honestly have no idea where to start with this. My 1996 Xj has the newer intake, with new IAC, TPS. I figured my map sensor went out so i unplugged it and it started running fine. but i can hear a vacuum leak and i have the left port on the bottom capped, the middle vacuum port open and the third port has a vacuum line that runs the firewall. The leak squeals from the middle but when i cover it cuts off or if i put another hose on it, it doesn’t change. Can anyone tell me the correct vacuum lines and if i need to get a map sensor. i want to replace lines and elbows everywhere in engine bay if possible. Thanks

 

You can easily check the operation of your MAP sensor with a very inexpensive and useful tool. Go to Amazon or eBay and get an ELM327 Bluetooth adapter. It plugs into your OBD2 diagnostic port. Link it to your phone through the "Torque Lite" app, which is free. Now you can select what sensors you want to look at, you can scan codes, and run all sorts of cool tests. I have one for every car of mine that's 96 or newer.

I'm suspicious that the MAP sensor is bad, based on the fact that you left the port open. You created enough of a leak to probably idle the engine up some, so that's probably why it runs "better".

Do you have a Check Engine Light on? Does the CEL come on when you first turn the key on? How many miles? Has there been any maintenance done such as spark plugs, cap/rotor?

 

See... That’s a great idea, but my OBD|| port isn’t working. But i have went through this last year and replaced distributor, spark plugs, wires, ECU, injectors, IAC, TPS, cold air intake, and everything on the belt is new. I was running and bending my own brake lines for the front because i put a 12 in lift on it and needed the brake lines to come down to the last pin on the frame. so in the process im assuming i damaged/ knocked a few vacuum lines lose since their so brittle. But my engine light comes on as it’s starts running bad. 216K miles

 

Hmmm. A 96. Not sure if you have OBD2 or OBD1.

You might find a vacuum diagram on Cruiser54'ssite. I think he has posted in a few times.


I like that color!

 

If the '96 has an OBD2 port, then its OBD2.

should be...it would be handy to find out why it isnt working, might be lacking voltage supply

you can use an old fashioned vacuum gauge to diagnose many engine faults, and use a "smoke test" to see if you can find where its leaking

"search function" and Google are your buddies

 

Not always. My 96 Ford van had an OBD2 port, and it drove the shop crazy because it wouldn't work. It had power, but nothing else worked.

Found an old timer at the Ford dealership who cleared up the mystery. There was a Ford-specific port hidden on a pigtail in the engine compartment, that was working. The OBD2 port was there because Ford had only partially implemented OBD2 that year.

Dunno if that kind of thing happened on any other vehicles, but that was a transition year for OBD2, so I think all bets are off.