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HPsauce

Poor starting - looking for suggestions as to why

Hi folks, my D2 S8 has become really bad in the last few days at starting from cold or warm; when hot it's usually OK.
It's also, for some time, suffered from occasional lack of power at low revs when cold, with no definite pattern, but usually when pulling out of a junction - inconvenient!

It's the 40V 4.2 V8 engine and I've recently changed the PCV valve and MAF (with no effect) and checked the inlet manifold flap operation is OK.

The symptoms are that it "sometimes" catches on the first turn of the key (it ALWAYS used to in all conditions) and if it does it chugs away with a cloud of unburnt fuel, firing on much less than 8 cylinders until they all get going, usually after about 15-20 seconds.
If it doesn't turn over first time it will need maybe 10 to 15 seconds of the starter motor and a bit of throttle pedal before again it starts chugging. In that situation I usually rev it a bit (2000-3000) for a few seconds after which it's fine.

Any thoughts what on earth might be going on?
Challice

When was it last serviced? Could just need some new plugs?
HPsauce

It's certainly due for a service, almost at 80,000 miles when I'm planning to give it the "Full Monty" including cam belt, water pump etc. etc.
Up to now it's had (via previous owner) Audi main dealer "long life" servicing, so god knows how old the plugs are.  
Manick

HPsauce wrote:
It's certainly due for a service, almost at 80,000 miles when I'm planning to give it the "Full Monty" including cam belt, water pump etc. etc.
Up to now it's had (via previous owner) Audi main dealer "long life" servicing, so god knows how old the plugs are.  


Then you'll have some work ahead of you... replacing the waterpump and cam belt kind of sucks... big time!


On topic: I'v had some problems with starts, mostly when the engine has been semi warm (around 20 degrees celsius), this was solved when i found a vacum hose connected to the throttlebody that was broken, never had thoose problems again!
HPsauce

Update: I found the cause, a failed coolant temperature sensor which I changed the other day. Easy enough to get out, but getting the retaining clip back in a right royal PITA.  
Manick wrote:
Then you'll have some work ahead of you... replacing the waterpump and cam belt kind of sucks... big time!

Indeed and no way I can do any of that myself; it's gone in today (to Fontain in Iver) to have all that done plus main service, new fuel filter, brake fluid etc. etc.  
Manick

HPsauce wrote:
Update: I found the cause, a failed coolant temperature sensor which I changed the other day. Easy enough to get out, but getting the retaining clip back in a right royal PITA.  
Manick wrote:
Then you'll have some work ahead of you... replacing the waterpump and cam belt kind of sucks... big time!

Indeed and no way I can do any of that myself; it's gone in today (to Fontain in Iver) to have all that done plus main service, new fuel filter, brake fluid etc. etc.  


Actually, its not really hard to do it, just takes a whole lot of time... Alot of stuff in the way to get to the belt and pump, im sure you could have done it with a pair of extra hands  
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