Month: January 2026

3S: Coil on Plug Installation / Fixes

Originally, the plan was to take the Stealth down for both the drive-by-wire (DBW) and coil-on-plug (CoP) installations at the same time, but as I was doing it, I realized there wasn’t much duplicate work and that it would be better to tackle one system at a time if any problems arose.

Well I wasn’t exactly planning on doing the CoP so quickly after the DBW, but while driving the other day I noticed coolant leaking from the thermostat housing… and of course it was probably the hardest hose to get off…

Leaky coolant line that goes to the rear turbo. The part that leaked was in between the crimp connector and the AN6 fitting

So to get that off I had to remove generally everything I needed if I was going to install the CoP, so I figured “while I’m down there” (the curse of all project cars)…

Rear Turbo Coolant Line Replacement:

Up to this point all the “an lines” I’ve made have been nylon braided ones and never a “PTFE” one. Had to do a little research on this, but really it’s pretty easy to do thanks to YouTube. Although the super thick wire cutters I used for the Nylon one was no match for this. So I had to resort to regular cut off wheels. I also didn’t see any reason to stick with a Banjo bolt. I talked to a few colleagues and none of us could come up with a reason we want to restrict flow. Per AI, a regular right angle connector would flow about 60% more coolant than the banjo bolt and since this is just cooling a turbo that gets notoriously hot, I figured that was a good thing.

A replacement PTFE hose has entered the room…

Installation of this went fairly easy. There were cheaper options available if I wanted, but now I have extra PTFE tube, extra connectors and everything. I thought about replacing the rear one as well but ultimately decided I wasn’t going to. I seriously have my concerns about the M12x1.25 right angle connector not leaking, but so far so good.

When I installed this, I had the AN line already tightened onto the elbow. I didn’t think I would have space to tighten the AN fitting onto the elbow and I appeared to be right. Thankfully there’s just enough clearance to fit the elbow on!

CoP Installation

Half the problem with the CoP installation was the fact I bought the kit used. In retrospect the amount of items missing and questions I had about it I would have been better off just buying a new one. There were bolts missing, spacers missing, no “cover” plate, etc. I also received “Hitatchi” CoP vs the Denso that R’Venge lists, but they appear to be the “Prius” ones also… so maybe just a swap? Who knows?

I determined the “spacers” were roughly 1/2″ OD x 1/4″ ID and 1″ in length. I bought these off Amazon and they appear to be a pretty good match. Was also missing the free bolts from it, they appear to be M8x1.25 and 45mm in length or so. I was able to re-use two of them, but they are barely getting any grip.

I followed the R’venge Installation Guide / FAQ and in general it was pretty accurate with few “gotchas”.

I also “hotwired” via relay the CoP so it got as much voltage as possible. I’m not the most happy with the engine bay wiring, but it wasn’t bad. Throughout this process there were a few times I was combining six wires into one (voltage, ground, and tach signal). What I think is the best method for this is the “Open Barrel Splice” and since I didn’t take any pictures of this, here is a great video from Motion Raceworks that shows how to do this.

The other thing I did in this installation was run all the Ignition wires directly to the ECU instead of through the factor PTU wires for three of them. I just felt like giving it a new direct wire could save me headaches later and since I was already going down that path it was best to just go ahead and do this. I tied them directly to the LinkECU Pin Function that was for that item, so Cylinder 1’s CoP went to Ignition 1, 2 to 2, etc. I am not sure in the LinkECU if you can change this outside of changing the firing order, but I figured this was the best case to just keep them tied to the right cylinder. If you go this route you’ll need new pins. I think I only needed the “smaller pins” but if you are ordering from Digikey you might as well grab some of the larger ones as the injectors are all the larger ones…

Small ECU Pins: TE 175265-1 (Most of the ECU Pins)
Larger ECU Pins: TE 175269-1 (ECU Pins 1, 2, 3, 12, 13, 14, 15, 16, 25, 26 )

My “heavily” modified ECU Pinout with the connector right next to it. This image was vital for me working under the dash plugging everything in.
Please remember to “cap” off any ECU pins you pull out. My preferred method is to use a label maker with 6mm heat shrink labels and to label them also. Then just heat shrink it over the actual pin. In the above image I eventually heat shrinked the “Turbo wastegate” over the pin. In the future if I were to do it again I would probably add what PIN it was originally.
Within LinkECU the settings to change are pretty easy. I changed it from Wasted Spark to Direct Spark and you need to change the firing order, prior to this it was Wasted Spark and firing order of 1-2-3-1-2-3.

R’Venge provides some starting Dwell times, went off “Prius” ignition dwell times I found online, but I’m not publishing it as I don’t know if it’s accurate or not.

Car all buttoned back up and adding coolant. I found this little “coolant” filling system on amazon a long time ago, none of the adapters fit directly, but I was able to find a way to make it work. This is before I turned the car on so I was only adding distilled water.

Bonus Round – “While I’m down there”

This is the shifter counter-weight for the six speed transmissions. One common problem is it hits the FMIC pipes in 4th & Reverse. I only had a problem with reverse. I cut it where you can clearly see with a oscillating multitool (as I felt it was the cleanest option), if I were to do it again I would cut on the redline instead.
I also finally cleaned my K&N filters. These filters have been on the car since roughly 2018, and have never been cleaned. While they didn’t drive that many miles (about 3,000) they have sat in dusty areas and everything. I bought the K&N Filter cleaning kit ( 995000 ) and used the cleaner part twice. Even after that the filter didn’t really look clean on it’s own, but once you add the oil it really turns red and looks good.