When I started my first K-Swap on a 2004 Honda Civic EM2, I knew nearly nothing about the whole topic. I got inspired by a few very impressive forum posts of people who already took the challenge to upgrade their Honda and they finally brought me to buy a used and dirty K20 engine from 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 come to the main reason I wrote this article. During my project which lasted nearly over a year I made many dumb mistakes because of my missing knowledge about the whole topic. I was able to find much useful information on the internet but sometimes I just had to find things out by trial and error. And what I can confirm here:
It was the best way to learn.
After you had removed and installed an entire engine, you have received and in-depth understanding how a motor is built up and how it operates in a car. Now I want to share my biggest insights I had and the things I would do different if I would do this swap again.
#1 - K20 Installation
The removal of the tiny 1.7 litre engine is easy. It can be easily attached to an engine crane and lifted out of the engine bay. I did the same for the K-Series engine: Installing it from the top. It is no science to realise that the bigger 2.0 or 2.4 litre engine needs more space. It was a challenge to bring this "monster" into the little engine compartment of the EM2 without scratching the paint.
Things are getting much easier if engine components like intake manifold, exhaust header and A/C compressor are not mounted while the motor is being lifted down. In the photo, you can see that I removed at least the exhaust header but I had to unmount the other parts too.
Maybe my engine bay's paint would look better now if I had followed this tip?
#2 - Wiring Of The Engine Harness
In the beginning I was afraid of the wiring job because it seemed so complicated to me. But if you do a bit of research and understand how the engine harness is built up and how it communicates with the rest of the car, this task will be no problem for you.
The main wiring job is all about the connection between the K20 harness and the chassis harness of the Civic. These two are plugged together behind the glovebox. Fortunately, the plug of the K-Series harness has the same design as the D-Series and it fits right into the other end of the chassis harness. The bad news: The pinout of the two harnesses are different which forces you to re-pin the K-Series harness plug.
There are some nice wiring guides on the internet which explain how to re-pin these plugs in detail. I printed out one of these sheets and went to the workshop with full motivation. Very soon, I realised that my plan to just re-pin the specific wires wouldn't work out.
The cable lugs which are fixed in the plug have different sizes. There are bigger and smaller ones. And, guess what, you have to pin in wires with the big cable lugs in slots where only tiny ones fit in.
It could be so easy!
I cut all the wires which had to be relocated and soldered the original cable lugs with the right size to them.
This was a nice and clean solution.
#3 - Wiring Of The Oxygen Sensor
The primary oxygen sensor takes a special role in the wiring topic. It is only partly 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 own build and
... it didn't work.
After I had searched through official Honda workshop manuals I found out that the wiring of the oxygen sensor(s) on facelift models is different. The guide I followed was referenced to a pre-facelift EM2.
Another interesting thing I came about after hours of fighting with thrown oxygen sensor error codes was the fact, that there are differences in the harnesses of USDM and EDM cars. My EM2 is a German model and it seems that Honda even changed the wiring between facelift models.
After I had done the wiring referenced to the service manual of the EDM 2004 Civic Type-R, it finally worked out and the error codes disappeared.
#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 nearly finished. The car was built back together and I already had mounted my license plates to drive. But the EM2 refused to leave the workshop. Maybe because he hadn't had seen any snow and rain for over nine months? The idle of the engine was extremely rough. It revved up and down after it had warmed up.
First thing I did was a vacuum leak test with the help of some brake cleaner. If you spray it in areas where the intake system has a leak, it gets soaked in and the engine is revving up for a short moment. Very easy way to find leaks. But be careful! Brake cleaner is extremely flammable. (Un)fortunately my engine had no vacuum leaks.
I continued my troubleshooting 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 can soak up in idle speed. It can clog up over time which can result in a rough idle. I removed and cleaned it but even that didn't help.
After a minute of cursing 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 will spare your nerves. 🙂