Really Rough Idle

[LAWG_rider]

Starting tonight my X started idling super rough. It will almost die in drive but never does. Sometimes in park it will almost die then the lights will dim for just a second before it revs back up. It's idling at around 750rpm like usual but its rough. There is no power loss when I am on gas and it runs fine as long as I am moving.

Could this be the alternator going out? An intake or vacuum leak?

Any input on what to check out would be great.

 

[walterd140]

Sounds like a vacuum leak. Check the tree on the motor, also check the brake booster thing on the fender. That may look like it is on when it isn't

 

[LAWG_rider]

Just looked and it is a vacuum leak from the tree on the intake manifold. The one without a vacuum line on it is looking from the driver's side 3 o'clock and closest to the intake manifold.

I looked around for a loose line and did not see anything but when I put my finger over it the idle went back to normal. Any ideas on what it is supposed to hook up to?

 

[nexis]

depending on the vehicle, a few of those ports will have plugs on them. Did you have a backfire durring startup recently, if so, those plugs are famous for popping off and getting lost, they sell them in a multi-pack at most auto-parts stores.

 

[walterd140]

Absolutely nothing! Don't know why they made a tree with a free plug, but my '94 has a plugged outlet. (Hint: a golf tee broken in half or a tire valve cap make excellent plugs for the bugger)

 

[TedJ]

They probably did use all those vacuum ports in some application, but not on the Explorer. Its cheaper and simpler to make one vacuum tree and put on a rubber cap than make ones with different amounts of ports.

BONUS: Makes it really easy to add a vacuum gauge.

 

[LAWG_rider]

I just went to the parts store and got the pack of caps. It runs fine now. Hopefully it will stay that way.

Thanks for all the help!

 

[walterd140]

Good to hear it was a simple fix. Truck On!

 

[nexis]

something that I've had great luck with on my truck is i squirted a little RTV into the cap before i put it on, had a problem of loosing a cap every other week, Cap with RTV has held strong for a year now.

 

[ctk]

truck still running good?