97 Ford Explorer- rough idle-and missing top end

[hoovdigity]

Hello,
I have a 1997 Ford Explorer XLT 4x4-4.0-SOHC-V6. Recently purchased used. Ford replaced motor at 90k vehicle has 107k. Had rough idle. Immediately did a tune up which consisted of new platinum plugs, wires, coil pack, standard air filter, fuel filter, fuel injector tank additive. Still having problems.
Problem #1-When vehicle is not moving and running, the idle goes from about 700rpm to 400rpm.
Problem #2-From a stop, if I hammer down the accelerator the vehicle climbs through all the gears up to 50mph with no problem. It is when I am at cruising speed of about 40mph and go to hammer the accelerator, the vehicle has no power, does not go over 3000rpm, it will hesitate and seem to miss. I had the catalytic converters checked and they said that are ok? They said to have the fuel pressure checked for a bad fuel pump, as well as checking the mass air flow sensor?
Problem #3-When vehicle is not moving and running, if I turn on the heater, the rpms will drop from 700 to 300 every 2 seconds and I can hear the A/C clutch clicking each time.
Problem #4-When turning on slight bends that require me to hold the wheel in the same position it seems like the wheel almost wants to lock up in that position. Happens left or right turns. Please help!-Thanks.

[shorod]

Sounds like at least a couple of your issues would be remedied by replacing the Idle Air Control (IAC) - Problems #1, #3, and #4. I trust that Problem #3 occurs when you turn on the defroster rather than the heat. The defroster will activate the A/C compressor if the ambient temp is above freezing, the heater should not. Caveat to this would be if you have the automatic climate control, then the Auto feature also enables the A/C compressor.

What type of platinum plug did you install? Some vehicles do not fare well with non-OEM plugs.

-Rod

[hoovdigity]

I replaced with a standard Bosch platinum. It appeared as if Ford replaced the plugs when they swapped the motor at 90k, cause they were in good shape. I was not able to reach the passanger middle plug, even with the wheel well plastic and tire off. I just replaced the wire. What do you think about the fuel pressure/fuel pump recomendation and the MAS air flow sensor?

As for the heater and A/C clutch, I do not have auto climate control. And the rpms move in all the heater positions.

[way2old]

Replace all plugs with OEM plugs. Ford seems to be sensitive to spark plug brands. Replace the plug you say you can't get to also. See if you can borrow a plug sochet that has 2 universals attached to the socket. That will give you the flexibility you may need to remove it. I agree with Shorod on the IAC causing the rpm fluctuations. You can try removing it and cleaning it before you buy one if you want.

[hoovdigity]

Great advice, cleaning the MAF,IAC, and throttle helped the fluctuation in the idle. I purchased the OEM plugs and will replace this weekend.

Thanks