When I started my first Honda Civic EM2 K-Swap in 2016, I knew almost nothing about the whole topic. I had gotten inspired by a few very impressive forum posts of people who already took the challenge to upgrade their Honda and they finally motivated me to bid on a used and dirty K20 engine on eBay. This was the first step of building my dream car.
You can follow the whole swap process in five episodes here:
But now I want to proceed to the main reason why I wrote this article. During my project, which lasted nearly over a year, I made many silly mistakes due to my lack of knowledge about the whole K-Swap topic. I managed to get a lot of free information from the internet but in some cases I was forced to find things out by trial and error. Today I know:
It was the best way to learn.
After removing and installing an entire engine, you'll gain an in-depth understanding on how a motor is built up and how it operates in a car. Now I want to share my biggest insights I had throughout the EM2 K-Swap journey and the things I would definitely do differently if I was about to swap another EM2.
#1 - K20 Installation
The removal of the tiny 1.7 liter engine is easy as pie. It can simply get attached to an engine crane and lifted out of the engine bay. I followed the same procedure for the Installation of the K20: Dropping it in from the top. It's not hard to tell that the bigger 2.0 or 2.4 liter engine needs more space. It was quite a challenge to fit it into the small engine bay of the EM2 without scraping the paint.
Things are getting much easier if some of the attached components such as intake manifold, exhaust header, and the A/C compressor are dismounted while the motor is being lifted down. In the photo, you can see that I eliminated at least the exhaust header but I would have been smart to get rid of the other parts too.
The engine bay would surely look better if I had invested this little extra effort.
#2 - Wiring In The K20 Engine Harness
The part of EM2 K-Swap I was worriying most about was the wiring because it seemed to be so complicated to me. But soon I realized that with a bit of research on how the engine harness is built up and how it communicates with the rest of the car, this task becomes managable.
The main wiring job is all about the connection between the K20 harness and the chassis harness of the EM2. These two are connected right behind the glovebox. Fortunately, the plug of the K-Series harness holds the same design as the D-Series and you can connect both plug and play. The bad news: The pinout of the two harnesses is different which requires a re-pin of the K-Series harness plug.
I managed to get my hands on a wiring guide which showed how to re-pin the wires in detail. Pumped up with confidence, I printed it out and headed to the workshop. But soon enough, I realized that my initial approach of just re-pinning the specific wires wouldn't work out.
The wire lugs which were inserted in the plug had different shapes! There were bigger and smaller ones. And, guess what, I had to move the bigger ones to slots which only accommodated the small-shaped wire lugs.
It could have been so simple!
I cut the particular wires and soldered the OEM wire lugs with the appropriate shape to them.
This was a neat solution.
#3 - Oxygen Sensor Wiring
The primary oxygen sensor takes a special role in the wiring topic. It's only partially included in the K-Series engine harness which means that you have to wire it in separately. I followed the wiring guide I had found before for my EM2 K-Swap build and
... it didn't work.
After I'd searched through official Honda workshop manuals I found out that the wiring of the oxygen sensor(s) on EM2 facelift models (04-05) is different. The guide I followed was solely written for a pre-facelift model (01-03).
Another interesting thing I came across after hours of fighting with O2-sensor error codes was the fact, that there were differences in the harnesses of USDM and EDM cars. My EM2 was a German model and it seemed that Honda had also developed different harness versions for different areas of the world.
After I'd finished the wiring with the help of an EDM '04 Civic Type-R service manual, it finally ran smoothly and the error codes disappeared.
Two years later we decided to bring all the information and experiences about the K20-EM2 wiring topic together and wrote an extensive wiring guide that covers all Civic EM2 models. You can find it here:
But let's move on ...
#4 - Wiring Of The Radiator Fan
After I had started the engine for the first time I was very excited to finish the build and bring the car on the street. But after a few minutes I had to shut off the engine because the radiator fan wasn't running. The stock EM2 fan switch, which closes the circuit of the fan after the coolant had raised above a specific temperature, was connected to the D17 engine harness. The K-Series harness has no plug for the fan switch.
I was forced to search through the workshop manuals of K20 powered cars again to find out how they connected the fan switch to the rest of the harness. After I had laid two wires to the fuse box and connected them to the fan switch relay, my fan was working and I was able to drive the car.
#5 - Idle Issues
I was almost done. The car was assembled back together and the license plates were mounted to hit the road. But the EM2 had other things in mind. The idle of the engine was extremely rough. It constantly revved up and down. Quite annoying with a loud exhaust.
The first act of troubleshooting I did was a vacuum leak test with the help of some brake cleaner. If you spray it close to a potential leak, it gets soaked in and the engine is revving up for a second. Pretty easy way to find vacuum leaks. But be cautious! Brake cleaner is extremely flammable. (Un)fortunately, the engine had no vacuum leaks.
I carried on and came about the idle air control valve (IACV). This tiny part is mounted to the throttle body and controls the amount of air which the engine soaks in while running in idle. It can clog up over time which possibly results in a rough idle. I dismounted and cleaned it, but that was a waste of time.
After a minute of shouting, I decided to replace the valve completely and the problem was solved. Before you ever install your K20 in your car:
Check and clean the IACV.
It'll make your life easier. 🙂
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