Transplanting a 325 eta with a 325i motor FAQ
Submitted by: Monty Sidhu (email@example.com)
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Last weekend, I installed an engine from an 87 325is in my 86 325es. This was done in my garage by my brother and me. Due to the many requests from others interested in doing a similar swap, here is how I did it.
Parts you will definitely need: The engine of course, with the harness (this should include the main harness connector ,motronic connector, all sensors and injectors), motronic unit, exhaust and intake manifolds, idle control valve, air flow meter and oxygen sensor (I had a complete "I" exhaust including the cat.) and the oil cooler with lines.
Recommended stuff: Bentley manual, ETM, clutch kit and a good hand cleaner.
The first step was to have the right tools which included a floor jack, jack stands, an engine hoist, plenty of metric sockets and wrenches and a set of torx sockets.
I had decided to remove the engine and transmission as a unit as they would be going into another car. Having done the clutch before, I really did not want to separate the two while in the car. To make things easy and safe, the battery and hood were removed from the car .
I first disconnected the power steering pump and the A/C compressor from the engine leaving the hoses attached. Next, all the wiring to the engine was disconnected which included the main harness connector on the firewall and the wires to the starter etc. at the junction box on the passenger side on the firewall. The motronic unit was removed and the wires pulled through the firewall complete with all the connectors. We then removed the radiator and all the cooling system hoses including the two at the back of the engine attached to the firewall for the heater. We then jacked up the car and removed the exhaust as a complete unit from the exhaust manifold to the muffler. We then removed the heat shield and the drive shaft. The wiring for the reverse light and the gear shifter were also removed at this time. We then attached the engine hoist to the engine using the two lifting points (one in front of the valve cover and the other to the right of the starter). Once the engine was supported, we removed the transmission and engine mounts and lifted the engine and transmission with the hoist. The only way to get this assembly out was by lifting the engine halfway and then lowering the car off the jack stands. This procedure does require some maneuvering to get the engine out without doing any damage. This engine was put aside and the new, to me, engine was bolted to a transmission using all new clutch components. We then lowered the assembly into the car. The installation process was the proverbial "reverse of removal". My biggest concern was that the wiring harnesses would not match up so I had bought the ETM's for both cars. Amazingly, the wiring is exactly the same between the 86 325es and the 87 325is and everything just snapped into place. The components that were not required with the "I" engine were the altitude compensator and some kind of sensor mounted on the passenger side firewall. I also installed an "I" tach. The only thing missing was the "check engine" light on the dash which I can do without. The only additional component used was the oil cooler. My 86 already had the holes to mount it in the lower front panel. All I needed was a couple of bolts and clips (they are the same as used on the radiator and available at any hardware store). I also had an "is" spoiler that has the cutouts for the oil cooler.
The moment of truth came when I turned the key. The first time, starter cranked and the motor turned over but would not start. I tried a few more times and on the fourth try, it sputtered for a moment and started running smoothly. After a few jubilant high fives and whoops between my brother and me, we noticed clouds of white/blue smoke spewing out of the exhaust. Big OH!OH! Shut it of immediately and looked around to see what the problem could be but could not find anything wrong. I started it up again and it idled perfectly but still spewed out clouds of smoke. With my heart in my mouth, I decided to do a test drive anyway. I started off down the street leaving a plume of smoke behind. Amazingly, after about .5 a mile, the smoking lessened and then completely went away. The car ran perfectly and I immediately noticed the significant power gain over the eta. I have come to the conclusion that the smoke was oil in the engine that went everywhere when we were removing/installing it.
PS: my beloved eta engine was not discarded. I found an 89 325I the same week with a blown engine, the eta engine has a new residence. This swap was a little more involved, mainly the electrical but, I'll save that story for another day.
Hope this helps other attempting a similar swap. Please let me know if you have any questions (I might have left something out in my hurry to go out and drive my car)