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Stoo.c
Monza


Joined: 07 Apr 2014
Posts: 159
Location: Hertfordshire


PostPosted: Sat Jan 06, 2018 6:42 pm    Post subject: C4S sounds 'funny' - dropped coil? Reply with quote

So not the best subject line in the world but I dont really know how to describe it.

I fitted a Top Gear exhaust and 200 cell cats about 2 months ago so still getting used to the slightly different exhaust tone which isnt helping me here.

About 2 weeks ago - the car sounded much different and I mean noticeably different - louder also whereby it was almost embarrassing - it wasnt a good loud. It sounded a bit poppy and when revving in neutral it was like I was driving my skyline. It had changed considerably since when I first fitted the exhaust - its meant to be the quieter of the Top Gear range - clearly this wasnt normal. At first I thought something had come loose so took it to my workshop and the exhaust is all bolted up tightly, new Oxygen sensors are still tightly in and there is no sign of exhaust leakage. I felt that the car was also holding back a bit but it could just be in my head.

However from cold when started the other day (I left it sitting for a week) it sounds absolutely fine and when revving it sounds normal and no popping at all. Its just when its warmed up.

My initial thought here is that one of the coils has packed up which would explain the noise and possible loss of performance and I'm also thinking this may also only exhibit itself when the car warms up if there is a crack in the coil for example. I would however expect to get an error code showing up telling me that there is a missfire on one cylinder but I've got nothing and when I plug my diagnostic in (granted just a generic one - not a super cheap one but not a super expensive one either), there is no sign of anything wrong.

Problem at the moment is I dont have time to mess about trying to work out if indeed a coil has packed up and if so which one. I actually have 6 spare coils from my old engine.

Keen to hear the thoughts of everyone before I take it in somewhere which I hate the thought of given in the last 5 years I'm the only person who has worked on this car. I struggle to trust many garages - so if anyone has a great recommendation in Hertfordshire of someone reliable, trust worthy and well prices, im all ears.
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kas750
Estoril


Joined: 31 Mar 2013
Posts: 3922
Location: Chorley lancashire

2006 Porsche 911

PostPosted: Sat Jan 06, 2018 6:52 pm    Post subject: Reply with quote

Plug it in to get a fault code and work from there.
 
  
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deMort
Shanghai


Joined: 21 Mar 2015
Posts: 4902
Location: Brighton


PostPosted: Sat Jan 06, 2018 7:05 pm    Post subject: Reply with quote

First suggestion .. move further south .. shall we say the Brighton area Very Happy

A misfire is most noticable on idle .. the car will feel very lumpy and shake a bit more .. as you rev it it becomes less obvious and as you say you should get an EML light on .

Its possible .. does the car behave as above ?

If its only when hot then obviously something is breaking down or messing about with temp and popping to me would kinda indicate a rich mixture .. fuel in the exhaust being burnt etc.

The " loud noise " is what concerns me atm , did you have the car hot and running when you checked the exhaust ? any leaks especially around the lambda sensors will cause problems .

I would like to look at lambda values , trim values and maf sensor readings first .. not sure if you can see any of that on your tester but if you can then get it hot and please post them .

Can you see a misfire counter or rough running with your tester as this would prove it and what cylinder .
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Stoo.c
Monza


Joined: 07 Apr 2014
Posts: 159
Location: Hertfordshire


PostPosted: Sat Jan 06, 2018 10:14 pm    Post subject: Reply with quote

kas750 wrote:
Plug it in to get a fault code and work from there.


As mentioned above there are no fault codes - I’ve already plugged in.
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Stoo.c
Monza


Joined: 07 Apr 2014
Posts: 159
Location: Hertfordshire


PostPosted: Sat Jan 06, 2018 10:21 pm    Post subject: Reply with quote

Demort where exactly are you based? I have several jobs that need doing and I’m struggling to find the time so it may well be worth me making a trip down to you as it would be good having someone like you working on it. Perhaps send me a message and we can go from there.

It’s definitely not shaking at idle - in fact feels fine at idle but I didn’t check the exhaust when warm - it was just after start up.

I think I’ve probably over played the popping a bit - most people probably wouldn’t even notice anything. I think I’m just paranoid after having a total engine destruction a year ago. Il take it for another proper one and get it warm to see if it’s even still doing it.

My code reader can do certain live data although I’ve never actually used it for that - probably need to have a read up in the book.

Thanks very much for the response so far
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Harv
Suzuka


Joined: 18 Sep 2014
Posts: 1202



PostPosted: Sat Jan 06, 2018 10:22 pm    Post subject: Reply with quote

Just a hunch but maybe you have a blowing gasket in the exhaust or on one of the manifolds that only shows properly when hot?

Worth a trip round the block and then close listen.


Coil packs tend to give a Check engine light long before you can detect something is amiss.
 
  
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Stoo.c
Monza


Joined: 07 Apr 2014
Posts: 159
Location: Hertfordshire


PostPosted: Sat Jan 06, 2018 10:28 pm    Post subject: Reply with quote

I agree and this is what I’m hoping. Unlikely to be the manifold gaskets as these haven’t been touched but obviously the manifold to Cat gaskets have been disturbed when fitting the new exhaust system. I reused the existing ones as they were only a year old but it’s possible the top gear flanges aren’t perfectly flat. I’m actually relatively unimpressed with the quality in general as nothing seemed to line up quite right. Maybe I should use the thicker fibre style gaskets provided with them as opposed to the original thin metal Porsche ones.
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Harv
Suzuka


Joined: 18 Sep 2014
Posts: 1202



PostPosted: Sat Jan 06, 2018 10:33 pm    Post subject: Reply with quote

You'll have tell tale soot at the joints if there's a leak.

I don't like the oem wafer thin gaskets and used the fibre ones when fitting my equal length stainless headers and they are a great improvement imo, seal is very good.

If they are leaking it may explain the popping as air could be being sucked in

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NLW73
Suzuka


Joined: 27 May 2014
Posts: 1192
Location: Yateley


PostPosted: Sun Jan 07, 2018 7:15 am    Post subject: Reply with quote

Easy way to check of you have a coil pack down or on way out is to start car from cold when up in the air then quickly feel the headers. If you have one much cooler one than the others then you know it's that one. Don't do when hot though.

Change that one and see what happens then. Saves a lot of fiddling around. If it was coil pack it would be lumpy as idle and car would struggle to rev.

It could be the new exhaust and cats bedding into the engine and they are going to be louder and different than before. Also the cats and exhaust need to bed in and get crap on them so their note will change as time goes on. You have a much more free flowing set up so sound will be different and louder.
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Stoo.c
Monza


Joined: 07 Apr 2014
Posts: 159
Location: Hertfordshire


PostPosted: Sun Jan 07, 2018 9:02 am    Post subject: Reply with quote

There certainly is a large amount of paranoia here without a doubt ever since my engine failure. I appreciate all the replies and when I get some time I will take it for a decent drive and see what’s what.
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