Everyone that's been into dsms for any lengthy period of time knows that the 90's have several endearing quirks...or not so endearing ones. The fact that they were the first year produced means that alot of things were changed with what they found out during the first production year.
One of those things is the Throttle Body. The 1990 Throttle body is unique in that it was changed out for the very next model year and that one carried through the 91-94. One of the better benefits of the 91-94 TB is that you can block off the FIAV.
I had a faulty ISC on my 90 throttle body and decided instead of paying a rediculous amount for a new ISC I would swap in a 91-94 throttle body that was "donated" by a good friend. Research on the net told me that the "only difference" was the wiring harness for the TPS. They were wrong...So I've put together a little write-up here for anyone who decides to follow in my footsteps.
Parts Needed:
91-94 Throttle body
91-94 TPS sensor harness (clipped out of a 91-94 engine bay harness)
91-94 Fuel Rail (this is a must as will be seen later)
Regular Screw Driver (for adjusting the BISS)
10mm socket and ratchet
12mm socket and ratchet
New Gaskets for the 91-94 TB to intake manifold
You will be pulling the fuel rail out of your 90, I discovered this the hard way, I simply thought I could slide the 91-94 TB onto my intake manifold and hook up the sensors. Unfortunately as you can see, the TPS collides with the way the fuel rail is formed.
Fortunately I had a 91-94 fuel rail laying around so I continued my project. Here is the difference between a 90 fuel rail and a 91-94
Step 1.
Because you have to replace the fuel rail, you will need to depressurize the fuel system. Undo the harness for your fuel pump and crank the car over until it no longer starts. Here is a photo of the harness in the rear portion of your hatch area.
It's a good idea to undo the negative on the battery after this step.
I will warn you, DO NOT SKIP THIS FIRST STEP! Fuel will spray out quite quickly and get all over if you try to remove your fuel lines without depressurizing the system.
Step 2.
Remove your 90 fuel rail (it's pretty simple, just use the 10mm and the 12mm sockets and ratchet and you should be set)
Step 3.
Remove your 90 TB
Step 4.
Install your 91-94 Fuel rail
Step 5.
Wire in the 91-94 connector for the TPS, the CORRECT way to do this would be to solder and shrink wrap. Unfortunately I did not have the piece of the wiring harness at the time I did this, so I used some clips for a temporary fix.
Step 6.
Install the TB...pretty straight forward, slide it on, bolt it down, redo the connectors.
Step 7.
Start the car, you may need to adjust the BISS in order for your vehicle to idle properly, it's also always a good idea to do a boost leak check. If you need help with either, check out
VFAQ Site - Visual Frequently Answered Questions for instructions.
1990 Swap to 91-94 Throttle Body
