Rough idle and EML flashing, coil packs?

Rough idle and EML flashing, coil packs?

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Gibbo205

Original Poster:

3,527 posts

206 months

Tuesday 21st October 2014
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Hi there

Got my 911 nearly four years ago now when it was around 4yr old with 25,000 miles, at purchase I had Mike at S&C fit new plugs and coil packs as old ones had signs of cracking. smile

Now fast forward to today, nearly 4 years later with 30,000 more miles and when I started my car tonight I notice what felt like a rough idle, firing on 5/6 maybe and seconds later the EML was blinking slowly. I though due to heavy rain and cold maybe water had got in somewhere so left it to idle for a minute and low and behold the EML went out and car drove smoothly home without issue.

Assuming it's time for new coils again? Car has had new plugs only a few thousand miles ago, but not new coils.

Rockster

1,508 posts

159 months

Tuesday 21st October 2014
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Gibbo205 said:
Hi there

Got my 911 nearly four years ago now when it was around 4yr old with 25,000 miles, at purchase I had Mike at S&C fit new plugs and coil packs as old ones had signs of cracking. smile

Now fast forward to today, nearly 4 years later with 30,000 more miles and when I started my car tonight I notice what felt like a rough idle, firing on 5/6 maybe and seconds later the EML was blinking slowly. I though due to heavy rain and cold maybe water had got in somewhere so left it to idle for a minute and low and behold the EML went out and car drove smoothly home without issue.

Assuming it's time for new coils again? Car has had new plugs only a few thousand miles ago, but not new coils.
Could be time for new coils. They can go off at any time. While 30K miles is not that many miles my take is UK climate is hard on coils. I was reading about coil problems posted by owners of UK cars long before USA car owners were posting similar problems.

However, I note the car received new plugs just a few K miles ago? What can happen is one (or more) coils doesn't get installed correctly, a frequent problem is the coil's connection to the wiring harness is not secure, and misfires can result.

So, if you are up to it you can check each coil's connection. Better yet would be just those cylinders that were misfiring.

The blinking EML (I take it UK speak for check engine light (CEL)?) was signaling a rich misfire. However, if the EML has gone dark there are no active error codes though there may be permanent ones, permanent in that they can only be erased by the DME after so many engine warm up cycles with the trigging error no longer present. You'll have to get an OBD2 code reader/data viewer for your car and check.

Now I have experienced something similar with my cars, both my Boxster and my Turbo. In the case of the Turbo it misfired at least 2 times, once after being out in a driving rainstorm all night and another time parked in a hotel parking lot when a real heavy fog moved in. The misfiring was very short lived but the CEL remained on.

The Boxster misfired once after being left parked up for a few days during which time the weather changed from dry to quite humid and damp.

You could just chose to ignore the problem for now. As long as the engine doesn't misfire at any other times nor exhibit any other untoward behavior put it down to the rain and vow to try to avoid subjecting the car to rain in the future.

IF this can't be avoided, then be prepared for misfires to appear the first start after a rain storm. As long as the engine's behavior is not scary and it recovers promptly and the light goes out (or remains on but solid) chances are the problem is not serious. It would be a good idea though to buy and carry with you a good OBD2 code reader data logger so you can right then and there read the codes -- write them down! -- and decide if you want to just clear them and continue or call in the calvary -- flat bed tow truck -- and turn the car over to a Porsche tech.

thegoose

8,075 posts

209 months

Wednesday 22nd October 2014
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Rockster said:
....put it down to the rain and vow to try to avoid subjecting the car to rain in the future.
rofl
You've not been to the UK have you?

No car that's done 30k in 4 years has done it only in dry weather I'm afraid.

medieval

1,499 posts

210 months

Thursday 23rd October 2014
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Just had all mine replace evenly for this very reason as well - my car does sit outside and I think after a particular heavy rain fall it ran very poorly the next day with the MIL light illuminate which does begin to flash if things get too hot and I think this can damage the cats if prolonged

Good luck

Gibbo205

Original Poster:

3,527 posts

206 months

Friday 24th October 2014
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Like I say never an issue before and it only flashes for about a minute whilst idling and was then fine. Not had any more issues since and it's being raining and cold, just not as heavy.

Still design911 had a deal on new beru coil packs and plugs for £240 delivered, so ordered. Shall get them fitted next week. Take no chances! smile

gsewell

693 posts

282 months

Saturday 25th October 2014
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I had the same in both my Subaru and a borrowed VW. Turned out to be some poor petrol. Give it a fillup with fuel from a very popular petrol station (especially with higher octane fuels they need a quick turnover) and see if it comes back again. If so, then either get your own OBD2 or visit your local OPC/Specialist for a Piwis diagnostic check.

Edited by gsewell on Saturday 25th October 10:45

nsm3

2,831 posts

195 months

Saturday 25th October 2014
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I seem remember you buying that car from Hagley (?) and your initial concerns, it being outside the OPC network etc?

If I'm correct, it looks to have served you well?

Rockster

1,508 posts

159 months

Saturday 25th October 2014
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thegoose said:
rofl
You've not been to the UK have you?

No car that's done 30k in 4 years has done it only in dry weather I'm afraid.
Actually, I have been to the UK, in an April, down in the Portsmouth area, though the hotel I stayed at was in Fareham. Business trip. I think it rained the whole 4 or 5 days I was there.

While it is less likely the coils are shot due to direct exposure to the elements they have to be suspect as the humidity and in some areas the salt in the air can exact a toll on the coils.

But just a loose coil connection can also be involved.