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Porsche Cayman 2.7, Seal Grey, 2007.
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Discussion Starter · #1 ·
Hi I'm baffled by a misfire and wondered if anyone might have advice for me. I've replaced the original Moll battery on my '07 Cayman 2.7 with a Silverline Bosch 74Ah ~ 750A which was listed at Europarts as correct fitment for my car. The car fired up and ran better than ever for about 30 miles and then suddenly developed a very noticeable misfire with the engine warning light and "take to workshop" dash display illuminated. The car has not long been serviced with all coil packs and sparkplugs replaced and apart from slow cranking was running well. Is it just coincidence this has happened after the new and more powerful battery has been fitted, or have I caused damage? Any advice would gratefully received.

Thankyou.
 

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Did you fill up with gas in those 30 miles? I just can't fathom how a new battery causes misfires.
 

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Porsche Cayman 2.7, Seal Grey, 2007.
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Discussion Starter · #4 ·
I didn't fill up on the drive but I've since topped up with premium unleaded and put the old Moll back on, but still the same result ~ misfire.
 

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Porsche Cayman 2.7, Seal Grey, 2007.
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Discussion Starter · #5 ·
Yes, the engine cranks stronger than ever and the charge voltage with the engine running is about 14.7 volts, which i believe is about right. Would a new battery show up or cause problems with the alternator? thanks for the interest!
 

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Porsche Cayman 2.7, Seal Grey, 2007.
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Discussion Starter · #7 ·
I was careful not to get the polarity wrong, but I could have flashed the positive lead. What damage could this have caused? Engine Management? Thanks.
 

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I don't know enough about the EMS on the Porsche to advise, but some other systems I've worked with don't take kindly to having the positive grounded while still connected to the battery. I would take a visit to your dealer or a good indy as soon as possible.
 

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Porsche Cayman 2.7, Seal Grey, 2007.
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Discussion Starter · #9 ·
I was just thinking, if i have damaged the EMS or some other electronic part, wouldn't it have shown up instantly rather than after a 30 drive? Thanks for the advice. I'm going out to have a look at it while the weather is good, make sure it isn't something obvious I've missed.
 

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Porsche Cayman 2.7, Seal Grey, 2007.
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Discussion Starter · #10 ·
Thanks to everyone who offered advice on my misfire. Turns out the newly fitted battery was just a coincidence and the real cause was just a loose coil plug that had worked its way loose (mustn't have been pushed on properly at the last service). Happy New Year to you all.
 

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Thanks to everyone who offered advice on my misfire. Turns out the newly fitted battery was just a coincidence and the real cause was just a loose coil plug that had worked its way loose (mustn't have been pushed on properly at the last service). Happy New Year to you all.
Seems like this is not incommon. A friend of mine recently had his Turbo serviced, tuned, new coil packs, track inspected, etc. After a long ride he had the same problem.
 

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Porsche Cayman 2.7, Seal Grey, 2007.
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Discussion Starter · #13 ·
They are fiddly to get to and of course I looked at the wrong cylinder bank first and found the problem last thing as the sun went down. Oh well you live n' learn. Cheers!
 

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It's good when these little problems are easy to fix. Happy motorin'
 
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