This is from back in my turbo days, but IIRC, the closer you get to the combustion chamber, the more accurate temp is recorded.
Consequently, if you pick an individual header pipe or similar, then you're may only pick-up a part of the engine's EGT. Probably right after the Y-pipe would pick up both banks, but still be close enough to be accurate.
I started tuning the MegaSquirt again but still have TPS problems and still don't want to burn up the engine.
Here's way too much information for you:
You can cure most TPS problems on the 5.2 by removing the sensor and cleaning the black contact patch with alcohol. Some disassembly may be required. Check the movement of the sensor as well. Next, take the holes that attach it and use a drill or Dremel and elongate the holes. Next reattach and using a meter, adjust the home position (with the ignition on, engine off) so it reads .7 volts - .45 volts is the stock reading. You can go as low as .25 volts without a problem. The TPS will sometimes have a "dead" spot at idle which causes a stumble under acceleration and can cause shifting problems on the auto transmission version. I cured my original Stinkerbutt (same throttle body that you have) by adjusting the sensor slightly past the dead spot to the high voltage side.
The problem comes from three areas. First, the little plastic piece in the throttle body that moves the sensor can get worn. Second, the fitting in the sensor itself can be worn. Third is the afore mentioned dead spot. By moving the sensor so it is "preloaded" against the spring, you eliminate most problems (preload can start at about .6 volts). In other words, move the thing until you feel the resistance of the internal spring, tighten and you're good to go.
NOTE: most of these problems are caused simply by the throttle body not engaging the TPS as you come off of idle - hence preloading the spring will probably cure it by itself.
Another problems with the sensor is a poor ground. You'll have to refer to the shop manual for the exact wire colors; it is blue/yellow stripe in most models/years.
On that engine you can also adjust the ignition timing. To do this, get to the bell housing on the passenger side. The sensor is attached just above the starter motor. Remove it and note that there are two rubber grommets. Remove them, elongate the holes, use washers on the bolts that hold it in and move the sensor (if I recall; you'll have to check this with a timing light) DOWN, which will retard the ignition timing a bit (about 2 degrees).
Another area in the Dodge Magnums (don't worry, the 5.2 was designated a Magnum) that will get you better mileage is to move the IAT (Intake Air Temp.) sensor to a hotter area. These sensors use resistance to tell the ECU what temp. the intake air is and adjust the mapping accordingly. You'll note that the higher the resistance, the colder the computer will think the engine is so you can't just slap a resistor inline. You'll get better performance but lower gas mileage. If you add 4k to it, it will always be in the cold map and get you some extra ponies when the engine is hot.
Refer to (one of) my web site for more TB mods for that style TB (videos too):
Crap, forgot. If you have my favorite problem of stumble, backfire, missing, surging when it starts to warm up, replace the distributor. Trust me, it took me and Dodge 6 months to figure that out by accident.
Proud owner of Stinkerbutt!
-Air Raid cone filter, direct to TB
-Homebrew front air dam
-Homebrew side skirt
-Torza top bed cover
-Now featuring front wheel canards!
I have my TPS modded and was showing 6.2v at idle and 3.74v at WOT and is spring loaded. It is also not that old.
The TPS problem I was having was the MS was showing it bouncing so was adjusting the fuel as such (accelerator pumping all the time so no fine tuning).
The distributor shaft was tight when I checked it when I had the engine out.
There was only a stumble coming off idle but the O2 gauge showed going lean off idle and I couldn't get rid of it but the TPS bounce was the main MS problem.
1998 Dodge DakotaSport 5.2 auto,
Cam advanced 4 degrees,
MSD Blaster2 Coil,
MSD 8.5mm SuperConductor wires,
Borg-Warner cap & button
and more to come...
When money is no object, one at each cylinder is best. To protect your cat place it directly across from the O2 sensor. Make sure and check before and after changes. Then try and find out what is normal temp.