Accelerate: The throttle cable

Since the SC doesn't have drive-by-wire (DBW) on the second generation body (or 1st depending on your country), the old fashioned throttle cable is used to open the throttle linkage butterfly valve to allow the engine to pull in more air. In this post I'll review replacing the cable. In the rare event it needs replaced, swapped for an automatic to 5-speed conversion, or GTE engine swap, don't worry as it's not a huge task. You will need a few tools (listed below) to get this job done

Note that in 1998-2000 years the throttle body designed changed with the addition of a VVT-i head so the part numbers in this post may differ for 1998+.

For my situation, the actual braided wire inside the cable casing was damaged during an engine transplant. The wire was crushed when engine was pulled from the bay and developed a significant kink which appeared to slightly affect throttle response. I'm not exactly sure how much affect this had, but it was bent enough to create some slack before the pin actually moved despite how stiff the cable is, so I decided to change it out.

Original cable with significant bend.

There were some side benefits to doing this procedure. One, I got to see how the wire was routed through the firewall and how it attached to the gas pedal. I had never seen this before and thought it was significantly more complicated than it actually is. It's hard to visualize that the hole in the firewall is so near to you while you're sitting in the driver seat. Also, the part is "new" despite probably sitting on a shelf for years and was less dry and stiff then the one I removed. The new unit's cable slid in and out of the housing much easier, which may change the throttle feel in some minute way. I suppose it's possible to oil/lubricate the existing one, but I'm sure this is not a part that needs replacing or maintenance under most circumstances. However it appears this is a common maintenance task on motorcycles with tools designed for this specific task, so it can't hurt.

I found a replacement part on Rockauto on sale during a wholesaler closeout for a very low price of about $25 with tax and shipping. I was suspicious initially because the part was branded as a Beck/Arnley part and I thought that maybe there might be some key differences in build quality or length. What I discovered was quite the opposite. The part was 100% exactly the same including markings, cable position, and coatings on the adjustment bolts. I suspect that either Beck/Arnley purchased these from Toyota during initial production for later resale, or they made all of them to begin with (likely under a parent company of some sort). No matter the history, the part is exactly the same. (Edit: it appears they buy from Toyota and later resell.)

Here are the part numbers for the manual transmission cable and approximate prices from Beck/Arnley and Toyota. If you're looking for the automatic transmission part number please scroll to the very bottom of this article.  I did mention the GTE swap earlier - you would likely need a Supra or Aristo, etc. throttle cable and I do not have those part numbers.

Genuine Toyota SC300 Manual Transmission Cable P/N: 78180-24070 - $65.00 + depending on dealer

Beck/Arnley P/N: 0950577: $25+ on sale

Replacement box.

Gas pedal end showing firewall mounts and ball weighted clip for pedal attachment.

Replacing the cable is quite simple and hardly daunting, but requires some dexterity and flexibility to maneuver under the footwell. 

Tools required: 

• 10mm socket and ratchet with short extension.
• Flashlight 
• 2x 12mm open ended wrenches (for throttle body side mounting clip)
• Needle nose pliers, or small tip screwdriver, punch, etc. to push throttle cable head/yoke?/pin out of linkage. 
• Paint pen / camera to note current cable adjustment nut position.

First, open the hood and remove the cable from the throttle body linkage. Rotate the linkage/spring all the way back as if you were opening the throttle body fully and make sure to hold it tight or have someone else hold it while you pull the cable towards you and rotate the throttle cable back and upwards. Then use the small pliers/screwdriver/punch/etc to push out the cable head from the guide slot towards the cabin/rear of the car.  If you get stuck here, just breathe, take a closer look at how the pin inserts into the linkage and try again.  Do not let the throttle linkage/spring snap shut with your fingers near it - this will cause injury. Slowly release it. 

Mark the position of the cable locking nuts on the guide slot (behind the throttle body.) 

Use the two 12mm wrenches to loosen the outside nut in the cable guide (the inside nut is typically glued/locked to a fixed position) and pull up to remove.

Note: earlier year SCs had a different style throttle body with an outside spring return. Later years have a wound coil spring, but the procedure is still the same.

Inside the car: 

To make things easier, move the driver seat back to the farthest position, raise tilt steering wheel to high (or leave key out of ignition if auto-retract is on) and find a comfortable position to reach under the gas pedal.

There's not really an easy way to explain how to remove the weighted ball end (shown above with the blue plastic clip) from the pedal. You need to see it and press the clip tabs, rotate, and once you take a look it's becomes apparent what you need to do. 

Remove the two 10mm bolts for the firewall mount.

Pull entire throttle cable unit from inside the car out through the firewall. Reverse to install; tighten mounting bolts near gas pedal, hook cable to gas pedal, lock cable in guide and push cable back into throttle body linkage. 

Before attempting to drive, leave the engine off and press the gas pedal a few times to make sure that it is not binding or getting stuck.
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Automatic transmission accelerator cable part number (genuine Toyota OEM confirmed for all years 1992-2000) : 
78180-24131