Low idle, black and smelly smoke

[Ghen]

Hello everyone,

Once in a while my ford explorer sport with 4.0 V6 SOHC gets low idle (around 400 -500 rpm) and generates black and smelly smoke at the exhaust pipe.
-It happens when start a hot engine.
-If I turn the engine off and on again it goes away and engine works fine.
-It happened once today and once around 2 month ago.
-No check engine light or code comes on.

Could it be a bad PCM?
What would you suggest?
Thanks.

 

[Ghen]

Anybody?

 

[donalds]

Might need a iac

 

[1998Exp]

Anybody?

Sounds like a defective coolant temperature sensor. If the PCM "thinks" that engine is cold when it's not, it will enrich the mixture (something akin to a choke in older engines). Hence the black smoke and poor idling. An out of range sensor or harness shorted to ground should set a code, but if it's just reading incorrectly and still in a reasonable range, probably not.

 

[Ghen]

Sounds like a defective coolant temperature sensor. If the PCM "thinks" that engine is cold when it's not, it will enrich the mixture (something akin to a choke in older engines). Hence the black smoke and poor idling. An out of range sensor or harness shorted to ground should set a code, but if it's just reading incorrectly and still in a reasonable range, probably not.

It happened again few days ago, but the temperature gauge was showing normal operating temperature. Is there more than one temperature sensor?

 

[fast_dave]

@Ghen

I like what @donalds wrote as well as @1998Exp wrote.

BOTH of these parts are prone to failure.

The IAC in the $40 - $60 range; and you seem to be moving extremely cautiously on fixing this condition (your original post is July 8th).

With that said, if you want to get on with it, the Temp Sensor is $15 - $16, so you might as well start with that

There's only One Temperature Sensor on your EX.

BUT - there are Two Different Wiring Harness Connector Types for your Ex!!!!!

Make sure you hands-on investigate before ordering - notice that at the top of each connector is different.

For this, I suggest Standard Motor Products offering - no need to throw money at this particular part.

Example One - Grey Connector: Standard Motor Products TX104 = $14.86 @ Rock Auto

Example Two - Brown connector: Standard Motor Products TS390 = $16.40 @ Rock Auto

Hope that helps and if it doesn't, move on to the IAC Valve!

Rock Auto Link: 2003 FORD EXPLORER 4.0L V6 Temperature Sender / Sensor | RockAuto

 

[1998Exp]

It happened again few days ago, but the temperature gauge was showing normal operating temperature. Is there more than one temperature sensor?

The dash gauge uses a separate sensor from the one connected to the PCM.

 

[fast_dave]

The dash gauge uses a separate sensor from the one connected to the PCM.

@1998Exp - Did I steer @Ghen on to the correct sensor or?!

 

[donalds]

Only thing I would add is buy both sensors .....the gray one is for the ecm. Orange is for the dash gauge..
We have good luck with aftermarket iac..s on here so I'd buy that at the same time
Imo

 

[BTR]

It's a royal pain to replace one or both of the sensors. Therefore, since you're going to have to get at them anyway, you (might) consider replacing both of them.

I can't speak definitively about the 2003 4.0L SOHC, but I can about the 2000 4.0L SOHC Job 1, 5-Speed Automatic O/D 5R55E, engine VIN E. For what it's worth, when standing in front of my 2000, looking at the front of my truck:

• The Coolant Temperature Sender is on the left. It drives the dashboard gauge. It does not report to the PCM.
• The Coolant Temperature Sensor is on the right. It reports to the PCM.

Beware! One or both of these sensors (might) be frozen into it's socket. Thus, when you attempt to remove the sensor, you'll accidentally damage the thermostat housing. Then, the housing will leak... and have to be replaced. This is a fairly difficult repair.

 

[donalds]

replace the whole thing with a metal unit and new sensors
Imo

 

[Ghen]

Gosh, all those repairs for an engine that might fail any minute!

 

[fast_dave]

@Ghen

About 36 years ago, my HS teacher Auto Shop teacher wrote the following on our classroom blackboard.

Just sayin' - All these years later, I've never found a way around it


"You can pay now, and play later,
or you can play now and pay later.
But either way, you will have to pay..."