Replacing the TPS
(Throttle Position Sensor)
Required Parts:
Torx drivers
Flathead scredriver - small
TPS Sensor
Optional Parts:
Air to Bowl Gasket (only found this in a rebuild kit)
Steps:
1. Diagnosis
2. Remove air horn
3. Switch sensors
4. Reassembly
5. Tune-Up
Step 1 - Diagnosis
This isn't something like changing the oil or putting on a new
air cleaner, this is taking apart the carburetor. Before you dive
into the heart of your car, take caution to make sure the TPS is
what is not working. First sign of TPS trouble should be an
engine trouble code. This will make your orange Service Engine
light come on. For me, it came on and stayed on while I drove.
Some codes a bad TPS would give would be 2-1, 2-2, and sometimes
I got a code 4-4, so 4-5 may be possible too. AutoZone has some
free diagnosis literature on the service counter that comes with
a key to check your engine codes. It also explains the next
procedure I'll go into, checking the voltage across the TPS
itself. After checking the engine codes, if they lead you to
believe the TPS may be at fault, you can check the physical
condition of the unit. The TPS is the 3-prong unit on the front
driver's side of the carb. Half is inside the carb, and the other
part is the connector. It tilts slightly downward and has a black
connector plug. First do a visual inspection on the condition of
the wires and to see if it is plugged in correctly. Next is the
electronic testing.
Step 2 - Remove air horn
Now by this point in time, you should seriously have a
service manual, preferably a carb rebuilding guide. It will tell
you better than I can how to do this. I think it is Doug Roe who
wrote the book the list prefers. I can get you through this but
I'd trust the book ;) Now back to business. There should be 9
screws to remove around the carb, 5 around the outside and 4 in
the middle. The last 2 screws are down inside the front part of
the carb. Don't drop these down there! The screws are all torx
bits of various sizes. You will have to unhook a few things on
the side of the carb before you can lift the airhorn off. Be
careful as to not damage anything. With everything removed from
the airhorn, carefully pry it up, being careful not to lose
anything. Make special note where the parts go, such as the
accelerator pump and the metering rods. Carefully set the airhorn
aside.
Step 3 - Switch sensors
You will easily be able to remove the old sensor as it slides
right in. Put the new one in the same way (plunger side up if you
forgot) and your swap is done. Sorry no pic of the disassembled
carb, but I was too worried about it going back together to snap
pictures.
Step 4 - Reassembly
Believe it or not, it all does go back together. Just take your
time, do it right, and keep checking that manual that you better
have bought! Put on the new gasket. If you need to change the
float, metering rods, jets or whatever, now would be a fine time
so you dont have to go through all this again.
Step 5 - Tune-Up
With it all back together, check your choke, timing, engine rpm,
and evrything else to make sure you are running properly. Clear
your engine codes and take it for a spin. Everything should be
better than ever now. If not, keep tuning until you get it right.
Most stuff is monitored by the ECM, so it shouldn't be too hard
with the right tools, and that manual ;)
Time Involved: 30 minutes - 1 hour
Difficulty: Relatively easy, althought working on a carb for the
first time is quite scary! Might want to have an experienced
helper or at least an excellent repair manual.
Approx. Cost: $30 - $60