ToxicGumbo's 2003 Toyota Tacoma 2.4L 2RZ-FE (23rd)
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Author:  ToxicGumbo [ Tue Sep 24, 2013 4:26 am ]
Post subject:  ToxicGumbo's 2003 Toyota Tacoma 2.4L 2RZ-FE (23rd)

FreeEMS engine #23, born at 9:45AM Central US in Manhattan, KS on September 22, 2013.


I bought this once-immobile truck off my brother, repaired it, fell in love with it's utilitarian nature, bought a bunch of offroad equipment, and caught FreeEMS fever.

Owner: Jeff Sheldon
Make: Toyota
Model: Tacoma
Engine: 2RZ-FE
Capacity: 2.4L
Power Adders: Tony Chachere’s
Firmware at first start: FreeEMS g0b1f3bc
Hardware: Jaguar A3
Description: RWD base model truck, automatic transmission, ridiculously riced up
Build Thread:

Image Image Image

Image Image

  • First start:
    [Zero tune, flat 50% VE, flat 10 BTDC timing, and no accel enrichment enabled. It ran so quietly, smooth, and easy at first start that I didn't realize it had turned over and tried to start it again (which led to the starter grind noise).]

Special thanks to:
  • Fred Cooke, creator of FreeEMS ( and good friend
  • Andy Goss, designer of the Jaguar ECU (
  • Mike Carpenter, author of EMStudio (
  • My girlfriend, Anna, and neighbor, Kyle, for their help and support
  • Everyone on and the #freeems IRC channels

If I can do this, anyone can.


Edit: Corrected firmware hash. Added date of birth.

Author:  Fred [ Tue Sep 24, 2013 12:25 pm ]
Post subject:  Re: ToxicGumbo's 2003 Toyota Tacoma 2.4L 2RZ-FE (23rd)

Nicely done, Jeff! :-) Index updated!

Author:  ToxicGumbo [ Mon Apr 28, 2014 4:39 am ]
Post subject:  Re: ToxicGumbo's 2003 Toyota Tacoma 2.4L 2RZ-FE (23rd)

Fred suggested I try a new firmware build and encouraged me to plug my Jaguar A3 board back into the Tacoma. Several life-changing events have happened over the past few months which sidetracked me, so I'm thankful for the prodding and extreme patience.

He also once asked if I had ever tried shifting gears (without any changes to the automatic transmission's wiring) to see if the vehicle would move. I hadn't. It didn't seem likely to work since the unit's wired up to be told which gears to change into. Nevertheless, movement seemed reasonable--perhaps it would honor 1st gear in reverse and forward. My main fear would be that the torque converter would remain unlocked and the entire transmission would take some abuse if I drove too far or fast, so I decided to keep the trip short if things worked. And of course, things did work! Here's a silent video of that first drive:

Here's a slick visualization Fred posted from my EMStudio-produced log file:


For reference, hIs comments on the log data:

Fred: EGO seems to be floating.
Fred: IAT seems to be a lie? 30C then falls to 27C while driving?
Fred: seems too hot?
Fred: your CHT warm up is gloriously obviously close to right, though :D
Fred: it had NEARLY warmed up when the log stops :)
Fred: 30% TPS
Fred: maybe we could get Jeff to floor it soon? :D

Exciting stuff!


Author:  Fred [ Mon Apr 28, 2014 11:36 am ]
Post subject:  Re: ToxicGumbo's 2003 Toyota Tacoma 2.4L 2RZ-FE (23rd)

you're like cheese - you take a while but the wait is worth it :-)

thanks for that, it made my day!

Author:  Hentai [ Tue Apr 29, 2014 12:10 pm ]
Post subject:  Re: ToxicGumbo's 2003 Toyota Tacoma 2.4L 2RZ-FE (23rd)

IAT seems right, it maybe hotter and then once going it will start cooling off.

Author:  Fred [ Tue Apr 29, 2014 7:31 pm ]
Post subject:  Re: ToxicGumbo's 2003 Toyota Tacoma 2.4L 2RZ-FE (23rd)

Check out the weather where he is ;-)

Author:  ToxicGumbo [ Fri Oct 24, 2014 6:01 pm ]
Post subject:  Re: ToxicGumbo's 2003 Toyota Tacoma 2.4L 2RZ-FE (23rd)

Long overdue update:

Even though I was able to start my engine off the Jaguar back in late September, 2013, the full conversion didn't take place until early July, 2014. A few weeks of driving around solely on FreeEMS awarded my truck an esteemed position on the Daily Drivers list.

The full conversion included shelving the OEM Toyota ECU, removing both O2 sensors, plugging one O2 hole, and running some extra cabling to support a 14point7 SLC AFR gauge and Bosch WBO2 sensor. The original O2 sensor wiring dropped out of the floor paneling and has left a hole which is still covered up by blue painter's tape (OEM plastic plugs are finally in the mail). During my next trip to Baton Rouge, I'll clip off an O2 cable end at a junkyard and use that to seal one of the unused O2 cables that's fairly well fixed in place.

There has been one service alert for the Jaguar board regarding a capacitor which I've recently changed out.

And there ya have it. For over three months I've been driving around on FreeEMS with a rough tune and no complications, despite the board baking in 100F+ weather and undergoing plenty of rough driving.

The next steps are to really nail out a decent tune and work on PWM idle control.


Author:  ToxicGumbo [ Thu Jun 04, 2015 8:53 pm ]
Post subject:  Re: ToxicGumbo's 2003 Toyota Tacoma 2.4L 2RZ-FE (23rd)

Updated my firmware this morning.

From: FreeEMS-0.2.0-SNAPSHOT-294-g3d1d9ea-TOXICTACOMA-MissingTeeth-Crank-36minus2.s19
To: FreeEMS-0.2.0-SNAPSHOT-301-gab84db5-TOXICTACOMA-MissingTeeth-Crank-36minus2.s19

Fired up so fast and cleanly I nearly soiled myself.

I'm on my own for two months, so I narrowed down the following as summer objectives:

  • Create a useful log for proper tuning
  • Configure a solid tune
  • Get PWM idle going
  • Rewire the load/run switch to the OEM airbag, key-based, switch and run a USB socket to it (side project: airbag flipswitches for easy off-road disable)
  • Step-up the feedback LED and connect it to the CEL/MIL
  • Work on cold-crank scenarios
  • Get started on turbo plumbing


Author:  Hentai [ Sat Jun 06, 2015 3:06 am ]
Post subject:  Re: ToxicGumbo's 2003 Toyota Tacoma 2.4L 2RZ-FE (23rd)

the auto should have its own tcm unless it was intergrated into the pcm. It maybe in some fail safe mode without ecu com, I would suggesting checking for a tcm and the pinout

Author:  Fred [ Sat Jun 06, 2015 4:15 am ]
Post subject:  Re: ToxicGumbo's 2003 Toyota Tacoma 2.4L 2RZ-FE (23rd)

Hentai, the auto in these old trucks is the same one I have in my Volvo, all mechanical, just a lockout on 4th/OD. No TCU required. :-)

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