What happens when a coil dies..... copied from an E31 forum:Had an owner have his 1991 Canadian spec 850 towed here as it was running on 6 cylinders. Car has around 230k kms (142k miles) on it. Ultimately discovered the passenger side coil had spilled its guts and self destructed as shown:
http://i171.photobucket.com/albums/u...4/IMG_0374.jpg
Which in turn, took out the corresponding DME:
http://i171.photobucket.com/albums/u...4/IMG_0375.jpg
Once both replaced, car started on all 12 but on road test, idle wouldn't drop below 1000 rpms and car was surging violently. Replaced EML and all is now better. This is not the first puking coil we have seen up here that has taken out a DME as well but the first to affect the EML. Perhaps a cautionary maintenance replacement of the 25 year old coils may prevent this expensive failure.
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Just as a follow-up. This was not an isolated case - it was the 5th E31 that I have had to do this diagnosis and repair on over the last couple of years. Other 4 were lower mileage J-specs and a US spec 6-speed car. I don't mind as I have plenty of coils and DME's on hand at the moment but I strongly urge you to replace your coils as a maintenance item. Using either OEM Bosch or aftermarket MSD 8207's will provide a stronger spark than your tired, worn out 20-25 year old OEM coils, improving reliability and even fuel economy and... maybe eliminate the additional cost of DME/EML replacement as well.... just my $.05 worth.
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What would you gents say is a good safe interval? From my recent fuel pump conversations it was suggested fuel pumps get replaced approx every 10 yrs as maintenance items. Would you say half that for coils? 5 yrs despite mileage?
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I have replaced at 35,000 - 40,000 miles. That works out to every 18-24 months.
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