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What needs to be replaced along with spark plugs?

1221 Views 6 Replies 6 Participants Last post by  mutyo051026
I bought my 03 e39 last April at about 150,000 miles and now it has 161700 miles. Since I don't know when the previous owner replaced the spark plug, I'm going to replace all of them with NGK BKR6EQUP this winter. I heard some people say I should replace the ignition coils and spark plug boots when I replace the plugs, but some people say replacing the coils when it's still woking is a waste of money (yes, replacing all coils are very costly to me :(). I'm not sure if there are any dead plugs, coils or wires on my car, and I don't really feel my engine is running bad.

If you were me, what would you do replace? (By the way, I'm also going to replace the valve cover gasket taking this opportunity.)
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No no need to change coils with boots unless the boots are cracked
And if you get rough idle and you scanned by obd2 and it tell you which cool went bad you do a trick swap it to different location and rescan and see if it's transferred it's your cool if it's not you have a short some where :(
I agree about the coils and boots.

I had a coil go bad that caused an intermittent low-RPM miss. The DME did not detect it. Only disconnecting each coil, one at a time, detected the bad coil.

Consider replacing the pre-cat O2 sensors.

Since you have no provenance on the car, consider replacing the trans fluid, as well as the ATF in the power steering, and the diff lube. The brake system is no doubt overdue for a flush.

The VANOS seals are probably toast.
LOL, and don't overlook the fan clutch and fan! I had my cooling fan explode at 151K, now I have nice dents in the hood! Worst part, this is not unusual. :(

Jim
- Take one spark plug out and examine it, if new, why waste your money?
- The coil: keep it until it is bad. In fact, get a few used coils on ebay (check Bremi vs Bosch) and throw them in the trunk as spare.
- The coil boot: mine was not too bad at 160K but I replaced them b/c some showed cracks (minor cracks) and each boot is only $5 or so.
+1, on everything CN90 said! :)
Although I only keep one spare coil, and I buy new ones off Ebay, rather than used. Oem Bremi with a coil boot for around $47 with free shipping. (I have had two coils fail between 230k and 250k miles...they are simple to swap out) Fortunately I already had a spare on the shelf, and just keep buying replacements to place back on the shelf as needed.
- Take one spark plug out and examine it, if new, why waste your money?
- The coil: keep it until it is bad. In fact, get a few used coils on ebay (check Bremi vs Bosch) and throw them in the trunk as spare.
- The coil boot: mine was not too bad at 160K but I replaced them b/c some showed cracks (minor cracks) and each boot is only $5 or so.
Thanks guys for all of your advice!!
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