What looked like "chocolate milk"?
MAF sensor often needs cleaning, especially for 4.0l computers
MAF sensor reports air volume to the computer so it can maintain a 14:1 ratio for air:fuel.
Since there would be a lag in response time between you opening throttle plate(foot on the gas) and MAF sensor detecting higher air flow, the TPS(throttle position sensor) was added.
TPS is similar to accelerator pump on carb, it allows computer to respond instantly to driver input, give that extra squirt of fuel, like accelerator pump did, when you press down on the gas pedal.
TPS sensor is very easy to test with a volt or ohm meter, it works the same as a volume control or a light dimmer, simple variable resistor.
NEVER EVER change a sensor without testing it first, EVER!
A $25 volt/ohm meter will save you $100's dollars in replacing perfectly good sensors.
50% of the sensors replaced by professional mechanics were not bad, but they still charged the customer, lol.
90% of sensors replace by DIYers were not bad.
Ever read a post like "I changed the TPS, the coil, the MAF sensor, the IAC Valve, but still have the problem??"
This is someone who should have spent $25 on a meter and saved himself some money and time.
Your issue could also be air:fuel mix related, engine is running too lean or too rich so hesitates when extra air is added(throttle plate opens)
Has your MPG changed recently?
If your spark plugs were black then you have been running rich or burning oil, swapping out spark plugs doesn't change anything, underlying problem is still there.
The O2 sensors also probably have a nice coating of "black stuff" if spark plugs did, so they should be cleaned, not sure it that's even possible, or replaced, but at least pull one out and have a look at it.
I assume the Check Engine Light(CEL) comes on with the key and then shuts off as it should, and that the CEL hasn't come on while driving?
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