Phil R Posted February 12, 2016 Share Posted February 12, 2016 Hi there, it's newbie Phil again, thanks to those who helped with replacement wheel thoughts, this time I need a bit of help regarding a rather strange 'knock' that is very audible on cold start up but then disappears after a few minutes. It comes from the engine and is as regular as a Swiss clock. You would almost think the car was an old Ford diesel if you couldn't see it. I've heard about ovalised pistons, big end bearing fails and cam belt tensioners and also 'it's normal, they all do this' but I'm obviously keen to diagnose what it is before something goes horribly wrong. Once the car has reached operating temperature there is nothing to hear so it's kind of hard for me to book into a garage as they won't hear a thing by the time I get there !! 😐 any pointers please? Thanks in advance. P Quote Link to comment Share on other sites More sharing options...
GeoffLeggy Posted February 12, 2016 Share Posted February 12, 2016 Hi, Does sound like piston slap to be honest. How many miles are on the clock? What oil do you use? have you checked it recently? When was it last serviced? 1 Quote Link to comment Share on other sites More sharing options...
Phil R Posted February 14, 2016 Author Share Posted February 14, 2016 Hi, it has 84,000 on the clock, last service at 68,000. Oil is fully synthetic and was changed last week. All advice welcome. Thanks. Quote Link to comment Share on other sites More sharing options...
stants Posted February 14, 2016 Share Posted February 14, 2016 Sounds like piston slap to me, wouldn't worry about it too much just don't be heavy with the right foot until she's up to temp 1 Quote Link to comment Share on other sites More sharing options...
Phil R Posted February 14, 2016 Author Share Posted February 14, 2016 Thanks for confirming this. it has all the symptoms. I go easy on the loud pedal at all times but shall make extra effort in this case. cheers P Quote Link to comment Share on other sites More sharing options...
Phil R Posted February 17, 2016 Author Share Posted February 17, 2016 so today my latest issue is a loss of power then surge then loss around the 2500-4000 rpm range. Some forums claim mass air flow sensor needing cleaning, others claim re-programming the ECU with a patch from Subaru that takes 30 min. The car is in the garage now and any help given to minimise the mechanics searching down the wrong path would be appreciated. It's most noticeable under load in 3rd or 4th. now we know the car suffers from a mainly harmless 'piston slap' - garage heard the nasty noise and said big end but that would remain beyond cold start up, mine disappears, but what is this strange loss of power? It's fully serviced and only has 86,000 on the clock so surely it can't be goodnight engine already? should I be making a new thread / post? Sorry if I should. Thanks in advance. phil Quote Link to comment Share on other sites More sharing options...
GeoffLeggy Posted February 17, 2016 Share Posted February 17, 2016 Hey Phil The end going would be noticeable at all temps but more so in the low-mid rev range. If you rev the engine up slowly when warm with no knocking its not the bearings likely to be gone. Not sure about a patch from Subaru, maybe another member can comment on that. Maf cleaning is easy so you can always do that yourself with little expense. If youve only changed the oil in the last 16K you could look at other simple service items like fuel filter, (not sure when due), air filter, plugs etc all can make a surprising difference. Try some injector cleaning additives, Wynns from Halfords is good. Just some simple inexpensive good things to get you started. Hopefully someone else can help with more specifics to your model. 1 Quote Link to comment Share on other sites More sharing options...
Phil R Posted February 17, 2016 Author Share Posted February 17, 2016 Hi Geoff, thanks as ever for your advice. Engine oil, Wynns flush and filter was done 2 weeks ago so that's cleared that. The car is immaculate and drives tight in every way apart from these new problems I'm incurring. I've done 2000 motorway miles in 3 weeks - I travel a lot and the 'spluttering' shall we call it, only occurred last Sunday on a very low speed drive home through country lanes so I don't think I've been sold a lemon - a hidden major fault would have emerged after 200 miles - at least in my mind ..... USA forums blame fuel type but I don't buy that, it's a modern petrol engine with minimal performance expectations - my friend drives an Audi RS5 which has a Lambo engine and he can throw any octane fuel in that and it works. i just replaced the front lambda sensor as the engine light came on for that, the garage changed it blaming faulty part but no change to the problem - it's some kind of simple (yet complex) fuel delivery issue. Totally stupid idea - un burnt fuel leaking through ovalised piston (slap cause) and turning engine into a 3 cylinder?? No that's engineering nonsense and reading too deep surely? The engine pulls like a race horse (well it did) so I suspect it's one of these inherent Subaru faults - but which one? Oh my Buddha let's hope it's nothing serious otherwise I'm going down the deathly road of 'Mondeo diesel to get me to work and back until retirement' !!!! thanks again Geoff for your help. Phil Quote Link to comment Share on other sites More sharing options...
GeoffLeggy Posted February 17, 2016 Share Posted February 17, 2016 So the most likely causes seem to be...... Dirty/old air filter Map revision from Subaru - hopefully your local dealer will shed some light Fuel - run out as close you can then fill with some V-Power and give it a thrash see what happens Maf issue - needs a good clean. Non of above will break the bank either Quote Link to comment Share on other sites More sharing options...
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