Sorry about the confusion with "sensor" & "sender", I just wanted to be sure that he would replace the correct one. The two "sensors" at the stat are for coolant temperature, one wire = gauge, two wires = PCM on a 2.9. The IAT, inlet air tempeature sensor, is in the upper intake on a 2.9 and in the newer 4.0s in the air inlet tube just before the TB. I can take some pics of a 2.9 if you would like to have them for reference, got one in the driveway.

 

Ken:

I could understand a one wire sensor/sender working when attached to the engine or any metal which is grounded. Anything mounted in plastic needs at least two wires to function. Like you said my IAT is mounted in the plastic intake tube on a 97 4.0L. It better have two wires as the book showed!!

 

I think that is why they still use a one wire sensor for the gauge and let it ground to the block but use a two wire sensor for the ECT since the ECT is more important to get a good signal. Your IAT will have two, I bet it's the exact set up that is used on my 2000 3.0.

 

Ken:

Like I posted above, electrical manual shows everything with two wires on my 97 4.0L. I'll see tomorrow when I get a chance to install that thermostat from my other thread.

 

Okay guys! I'm totally lost. I know what a MAF is, but apparently my 2.9L doesn't have one! I am a newbie, so be gentle! Apparently I need some sort of code reader to find out what's wrong, but in the meantime, I'm letting my 20+ years of "know-how" do the evaluating. I have no idea what the IAC, IAT, ECT, OSS, ODS, DPFE, TB, ATT&T, ICBM, CNN, ESPN, look like! much less where they are located and how to check and see if they are working properly! (I guess I need that code deally? )

Basicaly, my truck cranks up fine, idles fine except for a drop in RPM's like it's wanting to stall out after a few minutes, and it runs fine at cruising speed. It's missing terrible now, (it's gotten worse) but is only doing it when I accelerate. I am trying to determine which is the best route to take, should I look at "electrical" parts, ie; distributor, rotor, plugs, etc. or should I look at "fuel" parts, ie; fuel pressure regulator, injectors, fuel line filter, etc.

OR! Should I invest in a code reader and Factory Repair Manual? (I eventualy plan to do this, but is it pointless to try and find this problem without it?)

 

UPDATE:

This weekend, I replaced spark plugs, wires, cap and rotor. The cap and rotor is where I think my biggest problem was, they appear to have never been replaced.
I also located the temperature sender (two wires) and squirted some WD40 into the top where the wires go in, (I think that was what someone suggested.)

Anyway, it doesn't miss like it did anymore. I still feel a little hesitation when the engine is "under load", going uphill, etc. I took a look inside the throtle body, and it looks like the side of the motor where the plugs went in! black carbon/oil mixture is caked up all inside, so, I guess that's my project next weekend. Can I use Carb/Choke cleaner to clean that thing out? Any precautions or advice?

 

I'll start with what everything means.
MAF=mass air flow meter, measures the amount of air entering the engine and you don't have them, only 90 califrnia 2.9s got them.
IAC=idle air control valve, allows air to bypass the throttle plate to control idle speed, controled by the computer, located on the passengers side of the upper intake.
IAT=inlet air temperature sensor, measures the temperature of the air coming into the engine, located on the passengers side of the intake, below IAC.
ECT=coolant temperature sensor, mmm, located above thermostat and has two wire not one.
OSS=output shaft speed sensor, measure the output shaft speed, similar to a VSS (vehicle SS, on the top of the rear and is used for RABS and other things on newer trucks), it's on the tranny but you don't have one.
DPFEGR=differential pressure feedback exhaust gas recirculation, this monitors the EGR flow and returns a signal to the computer, I'm not familar with the type of EGR system used on your year.
TB=throttle body, the thing that has the throttle plate in it and when you step on the gas pedal the TP opens.
ICBM=internal crankshaft balance monitor, located right behind the AT&T (automatic transfer and traction module) and next to the ESPN (exhaust system pressure neutralizer), LOL.
Hope this helps with the terms. A code reader is not expensive ($30) so you might want to pick one up and pull the codes, it's not hard to do. If you do I have the 88 Ford manual and will help with the codes and pinpoint tests, except the EGR since it was gone by 88 and I'm not familar with them.

 

EGR = Exhaust gas Recirculation