They’re beautiful, fast and capable of going above and beyond the 100,000 mile mark if well maintained, but even a BMW 7 Series is probably going to need a few specific repairs and replacements along the way. Such is the case with the 740i, a BMW model known to have early engine issues with prematurely-worn spark plugs. Obviously these engine parts are vital because without functioning spark plugs, there is no spark, which means no ignition; and without ignition, a BMW is little more than a very expensive and pretty lawn ornament. However, before getting down to changing out the spark plugs in a 740i’s engine, it’s important to determine whether they are in fact the source of the problem. The following symptoms are indicative of degenerative spark plugs needing replacement parts in your BMW:
Diminished fuel economy – the miles per gallon is significantly lower than usual.
Engine misfires – signature “sputtering” sound from any exhaust and engine parts, accompanied by the check engine light.
Hard to start – engine turns over longer than normal before starting.
Reduced acceleration – probably the most noticeable symptom of bad spark plugs
While each of these symptoms can also be attributed to other causes, combined they suggest bad spark plugs are to blame.
To properly remove and replace the existing spark plugs in your BMW 740i’s engine, you will need the following parts and tools:
OEM BMW PARTS: Eight high-power platinum spark plugs, highly-suggested OEM-quality from BOSCH or Laser (SKU: BKR6EQUP or FGR7DQP); preferable to purchase from an online BMW parts supplier, as dealers will likely overcharge.
AUTOMOTIVE TOOLS: Torque wrench, 10mm socket, socket extension, spark plug socket, ratchet, flat head screwdriver, and anti-seize compound.
Before getting started on a spark plug replacement project, it’s critical to give the engine time to cool off. BMW engine bays are notoriously packed and padded to reduce noise, which has the side effect of holding heat a lot longer than other vehicles.
NOTE:It might also be a good time to change the oil, as operating a car with bad spark plugs will likely burn up oil.
- Remove the sound-reducing plastic covering from the top of the engine. This can be accomplished by pressing down on the four plastic plugs locking the cover in place, popping them out, and then popping the cover off.
- To the left and right of the exposed engine will be smaller rectangle coverings with “BMW” on them. On either side of the “BMW” will be two small square coverings within the larger covering. Using the flat head screwdriver, pry these off. Underneath will be 10mm bolts. Remove these to reveal the bremi coils.
- Remove the caps on the bremi coils by applying pressure with the flat head screwdriver on the metal tabs holding them on.
- READ BEFORE PROCEEDING: Label each bremi coil before removing! You don’t want to mix them up. A-B-C-D or 1-2-3-4 works fine. Using the 10mm socket, remove the nuts holding the bremi coils in place. Finally, remove the bremi coils. Don’t be afraid to apply extra force, as the bremi coils are known to be difficult to remove engine parts.
- The soon-to-be-replaced spark plugs are now visible. Unscrew them to remove. Signs of scuffing, oil, or debris are indicative of fouling. However, visibly healthy looking spark plugs may still be faulty and need replacing.
- If there is any visible oil or debris in the spark plug sockets or any other engine parts, gently clean with a soft cloth. Twirl slowly using the flat head screwdriver to get into all the nooks.
- Apply a dab of high quality anti-seize compound to each new spark plug (along the screw-grooved end).
- Install the new spark plugs using the torque wrench, and abide by the parts-manufacturer’s suggested foot-pounds ratio. BOSCH suggests 21 ft. lbs torque.
- Reinstall the bremi coils and their caps.
- Put the plastic coverings back over the coil packs and other engine parts. Project Complete!
If faulty spark plugs were to blame, your bimmer ought to start up right away, firing smooth and staying that way. You’ll get back optimum fuel economy, and acceleration will be noticeably more responsive!