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stevew30

cold start problems 2004 cayenne s

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I have a 2004 Cayenne S which has a number of problems when startingon cold. All the garages I take it to just plug in the computer and say it is reporting no faults, so therefore there is no problem !!

The problems are:

1) sometimes it just will not start. I turn the key and the engine turns but it will not fire. It takes about 5 - 10 attempts to start it, and when it does, massive amounts of smoke come out and it smells of petrol

2) there is a problem with the cold idle speed. It starts at 1000rpm and then settles at 600rpm. however sometimes it wil drop and bounce between 200rpm and 400rpm. This causes it to stall in slow moving traffic...but it is an auto !!

3) the engine runs very lumpy when it is cold - almost like a misfire. I have had the coil packs replaced which seems to fix it for a short while, but then it starts again.

When the engine is warm, it runs very smoothly and is just fine. It is just the first 10 mins or so that are a problem.

Any help appreciated !

Steve

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Sounds to me like it could be a temperature sensor giving a bit of jip! They are funny things sometimes not giving any fault codes either, depending on what type is fitted 2 or 4 pin. Im not too sure but being as its falls into the VAG group kinda thing they could be pretty similar.......not meaning to insult.

The way they could check it and how i do using VAS equipment is from first cold start using the oscilloscope on on draw mode(Not too sure what the Porsche boys are using in the form of diagnostics sorry) the signal side of the temp sender if its a 4 pin or just scope the 2 pin. Generally you should get a smooth signal gradually coming down from approx 5 volts and then even out once up to operating temp. its the sort of thing me personally would checking.Why did you replace the coil packs and which engine have you got, size and code if applicable and cylinders please.+++

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TD - A Cayenne S will be the normally-aspirated Porsche V8.

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Thanks TD.

It is a 4.5 v8 engine.

thanks for the advice, will get the garage to check it out.

Cheers,

Steve

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Pretty old thread but loads of these suffer from crappy plastic pipes breaking down in the'V' of the engine, causing running problems.

Porsche sell a replacement part and associated pipe work made of metal, which it should have been from the start, but it ain't cheap.

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Or the block is shagged. Very common on the S, they suffer similar issues to the 996 engines with bore scoring, etc.

Get it to a decent Indy and get it borescoped. My local Indys rebuilt one last year from a new block from Porsche, it was as expensive as it sounds I'm afraid.

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Bore scoring is something I can across when I was looking at getting one of these. Lots of owners reporting it. One of the reasons I ended up with a 4.4 X5 instead. Hopefully yours is a simpler fix.

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On that note actually, I do believe you can hear it quite clearly. A distinct piston slap. Are you hearing anything like that?

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There is meant to be a characteristic sound, yes.

On the flat sixes, it also shows up as one exhaust being sootier than the other. If you have two separate exhaust channels then you could look for that as well?

Edited by patently

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