brantley55

When i start my cherokee its sputtering really bad and when you rev it in neutral black smoke comes out of the exhaust. what could it be?

cruiser54

MAP sensor tube
There is a brittle little tube. It comes out of a rubber plug, low on the engine side of the throttle body. It runs back to the firewall, then up to your MAP sensor, behind the valve cover, higher up on the firewall. It has one vacuum line as already mentioned, with a 3-wire plug in the bottom.
CRUCIAL!! The MAP sensor will tell the ECU to dump fuel with little to no vacuum to the MAP. Any crack or blockage and it will be pig-rich. ( black smoke, fouled black plugs, must hold your foot to the floor to keep the engine running). You can pull the line off the MAP sensor and feel for vacuum with your finger. If it runs!
A visual inspection usually reveals any issues with the line from the throttle body to the MAP sensor.

brantley55

that line wasnt clogged at all, had nice vacuum to it

cruiser54

Unplug the MAP and plug it back in , after inspecting the connector.

Is the plastic clip still intact?

brantley55

the connector looks fine, clip still intact.

cruiser54

Black smoke is caused by MAP, CTS, IAT. In that order.

brantley55

Coolant temp sensor can cause black smoke?

cruiser54

Yes, if it's telling the ECU the engine is real cold when in fat it's not.

Not as bad as a MAP will though.

brantley55

what about the o2 sensor? and it only sputters at start up, after like 5 minutes it evens out and smoke goes away

cruiser54

Possibly, but not likely. I would replace it if you've never done it.

Have you ever done the ground refreshing and sensor ground test?

brantley55

ok so heres what happen.

this morning i threw on a new o2 sensor. i hoped on the I-17 and headed up north, i was climbing the hill right before crown king exit and white smoke started coming out of the exhaust. what could it be?

cruiser54

White is usually coolant.

brantley55

meaning what? keep in mind i did seafoam about a week ago

cruiser54

Sure it doesn't have a blue tint to it?

brantley55

not a 100 percent sure,because i was driving when the smoke started coming out and all i saw was white