The following article gives detailed instructions on replacing the spark plugs and coils in a BMW vehicle with the N62 8 cylinder engine. Even though we have used a 2005 BMW 645ci to perform this repair, this article can be applied to any BMW 5,6,7 and X5 series vehicle with the N62 V8 engine with minor modifications.
A BMW N62 engine tune up may help cure your rough idling 8 cylinder engine.
There is one thing we definitely need to give BMW credit for with the 8 cylinder N62 engine…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 their vehicles. But don’t get us wrong, we are pleased it is up there. The fuel injected V8 in the front of their luxury coupes, sedans and SUVs literally catapults them 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 leaves a microcosm of space in the engine bay, making a relatively simple repair like a BMW N62 engine tune up quite challenging.
A BMW N62 tune up involves replacing the engines spark plugs and ignition coils. BMW left very little space between the N62 engine and the inside of the fenders, making it necessary to remove parts and squeeze your fingers into tight positions to complete the repair. The good news is a BMW N62 engine 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 BMW Service and Warranty Information manual for vehicles with the N62 V8 engine recommends replacing the spark plugs every 100,000 miles. Even though the recommended schedule for replacing the ignition coils it is not specifically stated in the service and warranty manual, the BMW Repair Guide strongly recommends replacing them with the spark plugs. 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.
1. Ignition coils (required) – Always use a high quality ignition coil when performing a BMW N62 engine tune up. Cheap aftermarket coils have a high failure rate and do not perform on the same level as OE quality parts. Interested in buying all of your coils and spark plugs together? Please see option 3 below for everything in kit form!
2. Spark plugs (required) – Always use a high power OE quality spark plug in your BMW N62 engine. Interested in buying all of your coils and spark plugs together? Please see option 3 below for everything in kit form!
3. Ignition coil and spark plug kit (optional) – Save money by ordering all of your spark plugs and ignition coils together in one kit.
- Unbolt the top engine cover by removing the four T30 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 housings 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 ignition coil clamps using an E7 external torx socket. Due to the limited space, we find a 1/4″ drive ratchet with a 6″ extension works great for removing the ignition coil clamp mounting bolts.
The following steps were performed on a 2005 E64 645ci. Please be aware that if you are using this article to tune up your 5,7 or X5 series vehicle, the steps may slightly vary. As stated at the beginning of this article, space is limited in the engine compartment making it a challenge to remove the ignition coils and spark plugs…especially the ones on the rear cylinders. Never use dielectric grease on the ignition coils during reassembly…it will cause the ignition coils to slip off of the spark plugs and cause cylinder misfires.
- Start the ignition coil and spark plug replacement at cylinder one (see cylinder chart above). In order to remove the ignition coil 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 it out of the way of the number one ignition coil.
- Unsnap the ignition coil’s plastic locking mechanism and remove the coil plug. Use a ratchet extension to help pull the coil loose of the spark plug. Remove the ignition coil from the engine.
- Using a 16mm magnetic spark plug socket, remove the spark plug from cylinder 1.
- 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).
- Insert the coil plug back into the ignition coil and close the plastic locking mechanism until it snaps shut. It is very important that the coil plug is pushed in as far as possible to avoid engine misfires. Never use dielectric grease on your ignition coils. It will cause the coil to slip off of the spark plug and cause a misfire.
- Please note that it is very common for the ignition coils to “slide up” on the spark plugs until their clamps are reinstalled. One you reinstall the ignition coil clamps, the coil packs will be forced down on to the spark plugs and will lock them into place.
- Continue replacing spark plugs and ignition coil on cylinders 2 and 3.
- Cylinder 4 on E63/E64 6 series vehicles 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 ignition coils 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 ignition coil clamps. Double check 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.
After completing your BMW N62 engine tune up, but 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 a diagnostic scanner to determine which ignition coil(s) is the culprit (the diagnostic scanner will show you which cylinder is misfiring). If you don’t have a diagnostic scanner, 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. This is very common on the during a BMW N62 engine tune up. You most likely have a coil plug that is not seated correctly. Go through every coil and use your fingers to make sure the plug is firmly seated.
- Once your engine is running smoothly, follow steps 1-8 in reverse to reassemble the engine bay.
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.
|BMW||E65||B7 Alpina||N62 4.4L|
|BMW||E70||X5 xDrive48i||N62 4.8L|