BMW 645ci Tune Up – 4 Hours
A BMW 645ci tune up can be performed in your garage and save you a huge amount of money; that is if you are willing to exercise patience and endure a couple of scraped knuckles and forearms.
There is one thing we definitely need to give BMW credit for on the 645ci…they figured out how to put ten pounds of parts into a five pound engine compartment. The BWW engineers were very clever in squeezing a 4.4L V8 into the front of this vehicle. But don’t get us wrong, we are pleased it is up there. The fuel injected V8 in the front of this luxury coupe literally catapults it down the highway, much like a small block chevy does in the Camaros and Chevelles of yesteryear. But unlike the GM carbureted small blocks of the 60’s and 70’s, the BMW V8 in the E63/64 6 series leaves a microcosm of space in the engine bay, making a relatively simple repair like a BMW 645ci tune up a…well…pain in the ass.
“…a BMW 645ci tune up is very “doable” for the home mechanic, and can literally save you well over a thousand dollars by not taking the vehicle to the dealership.”
Or even better….a pain in the fingers and forearms. BMW left very little space between the sides of the engine and the inside of the fenders, making it necessary to remove parts and squeeze your fingers into tight positions just to remove and reinstall the coils and plugs. Not fun. But the upside to all of this is a BMW 645ci tune up is very “doable” for the home mechanic, and can literally save you well over a thousand dollars by not taking the vehicle to the dealership.
The spark plugs and coils should be replaced every 60,000 miles on your 645ci. Symptoms of worn plugs and coils can be rough idling, poor acceleration and overall performance and shoddy fuel economy. Keep your plugs and coils on a regular maintenance schedule to fully enjoy the true performance of your BMW vehicle.
Tools and Supplies
1/4″ drive socket wrench
1/4″ drive 6 in. extension
3/8″ drive socket wrench
3/8″ drive 6 in. extension
3/8″ drive 5/8″ spark plug socket
Flat blade screwdriver
- Unbolt the top engine cover by removing the four torx bolts.
- Remove the two side engine covers. They simply snap into the sides of the engine and can be pulled loose with your hand.
- Next, you will need to remove the cabin filter containers from the back side of the engine. Start by removing the cabin filter cover by pressing the side tab and sliding the cover off.
- Use a flat blade screwdriver and an 8mm hex socket to remove the cabin filter containers.
- Next, remove the right air inlet with an 8mm hex socket and a T20 torx bit.
- Repeat above steps with right cabin filter container and air inlet. Note the hood electrical connector will need to be removed from the right cabin filter container.
- Remove the four coil pack clamps using an E7 universal torx socket and a 1/4″ drive ratchet with 1/4″ drive 6 in. extension (see Tools and Supplies list above for photos of these items).
- Start the coil pack and spark plug replacement at cylinder one (see cylinder chart above). In order to remove the coil pack from cylinder 1, you will need to loosen the power steering fluid reservoir. Use a 10mm wrench to remove the two nuts securing the reservoir to the engine compartment, and slide out of the way of the number one coil pack.
- Unsnap the coil pack plug hold down and remove the coil plug. Use a ratchet extension to help pull the coil loose of the spark plug. Remove the coil pack from the engine.
- Using a 5/8″ spark plug socket and a 6″ ratchet extension, remove the spark plug from the spark plug tube.
- Apply anti-seize lubricant to the threads of a new spark plug and reinsert back in the spark plug tube. The anti-seize lubricant keeps the spark plug threads lubricated so future installations are easy. Hand tighten spark plug using just the socket extension.
- Use a torque wrench to tighten spark plug to 25 Nm (18 ft-lb).
- Add a small amount of dielectric grease to the end of the spark plug boot. The grease helps to keep the spark plug boot from seizing to the spark plug making future replacement easy. Reinstall the coil pack on the spark plug.
- Insert the coil plug back into the coil pack and close the coil plug hold down until it snaps shut. ***It is very important that the coil plug is pushed into the coil pack as far as possible…if not engine misfiring can occur.
- Please note that the coil packs will continue to “slide up” on the spark plugs until the coil pack clamps are reinstalled. One you reinstall the coil pack clamps, the coil packs will be forced down on to the spark plugs and will lock onto them.
- Continue replacing spark plugs and coil packs on cylinders 2 and 3.
- Cylinder 4 is a bit tricky…it will require the loosening of an air conditioning freon line bracket so enough room can be created for removal of the plug and coil. Use a 10mm open end wrench to remove the two nuts anchoring the bracket to the engine bay. Carefully pull the bracket towards the engine and slide the coil pack out behind it. This step takes a lot of patience.
- Cylinders 5 through 8 are a little bit easier than 1 through 4. There is not need to remove any parts to get the coil packs and plugs out of the engine. Once again, use patience and persistence…never be afraid to walk away from the job for a while to avoid getting upset.
- When all of the coils and plugs have been replaced, reinstall the coil pack clamps. Once again, use force with your fingers to make sure the coil plugs are pushed in as far as they can go to avoid a misfire when you start engine.
Testing and curing misfiring engine
Before you finish reassembly, start the engine to make sure it is running properly. If the engine runs rough and the check engine light comes on, you will need to hook up your diagnostic tester to determine which coil plugs are not seated correctly in the coil packs (the diagnostic tester will show you which cylinder is misfiring). If you don’t have a diagnostic tester, visually inspect each coil plug to make sure it is pushed in all the way. If your engine is running rough after completing this repair, don’t panic! You most likely have a coil plug that is not pushed in all the way.
Once your engine is running smoothly, follow steps 1-8 in reverse to reassemble the engine bay.
If you have any questions or comments, please feel free to contact us. And congratulations for Doing It Yourself!
The Repair Difficulty Level displays graphically how challenging the repair is, from easy to advanced. Easy repairs usually require very few tools, have short repair times and do not require jacking and supporting the vehicle. As the difficulty level rises, expect the repair to demand more time, specialized tools, and better understanding of mechanics to complete the job.