Odd issue this morning, loud banging / tapping with rough engine

[foxdie]

Hi all,

I'm not sure if this is detonation or not but I'd like to check with you guys. Firstly, for future reading of this thread to describe the conditions, my car hadn't been driven for 24 hours with very cold weather (between 0'C and -10'C depending on time of day).

I went to start my car this morning and *slaps head* forgot I had a manual, I turned the key with the car in reverse and naturally you can imagine the car didn't start

I took it out of gear and she started normally, I whack the heater on full and the rear de-mist and start de-icing the car, as I'm prancing around the car like a homo in the cold the car slowly goes from the cold/fast idle norm to something quite lumpy and rough.

I finish de-icing the car and jump into the car and blip the throttle and it was running so rough that the car was shaking and I think to myself "it's just been stood in the cold too long, it'll clear up as I drive to work", as I back her off the drive in this state there was a noticeable bang / clang, almost as if someone had loudly tapped a spanner on something metal under the engine.

At this point I've stopped in the middle of the road and a cars coming down the hill pretty quick, so I set off rather sharpish and the car really didn't wanna move, running like a bag of bolts accompanied by another clang.. so I back off the throttle completely and coast down the road which she seemed happy to do.

As I continued my journey to work the problem seemed to disappear, I had one more clang trying to climb a road (was a bit on boost at this point) but then as I near the end of my 30 minute journey the problem had completely disappeared and I could boost without any issues.

Anyone know what this was and what could have been the cause? The car is having a major service this weekend so hopefully that might resolve it, but if it's something more sinister I'd rather be prepared to fix it now whilst I've got a few quid in my pocket than in a month when I'm back to normal.

Thanks in advance

[Subaru ETA]

The running rough could be it over fueling with the cold weather and I wouldn't worry about it. But seeing as it was accompanied by a clanging sound, well that don't sound too **** hot!

[elnevio]

Not the sort of sounds that accompany something which goes away?

But if it's not even igniting in a cylinder or two (dodgy spark plug, etc) then maybe that's not too bad and it's actually fine, and could well be resolved by the service. It seems the really cold weather is bringing out a few nasties! Hope it's an easy one.

[foxdie]

The running rough could be it over fueling with the cold weather and I wouldn't worry about it. But seeing as it was accompanied by a clanging sound, well that don't sound too **** hot!

Not the sort of sounds that accompany something which goes away?

But if it's not even igniting in a cylinder or two (dodgy spark plug, etc) then maybe that's not too bad and it's actually fine, and could well be resolved by the service. It seems the really cold weather is bringing out a few nasties! Hope it's an easy one.

It was weird, my car does have a misfire (and it was doing it a lot today), is it possible the mixture was igniting in the exhaust manifold to cause that noise?

(If so I bet the cats ****ed now, good job it's being taken out soon)

[swinks]

Why then you have pretty stable idle when started from cold? Knacked coils or plug wouldn't give you stable idle.
Shaky and rough... maybe cambelt snapped 1 tooth and timing gone wrong. Whilst cold symptoms were worse than later hot engine.

[foxdie]

I don't think that's it, if the cambelt had slipped a tooth, why would the car be back to normal and pull hard on boost near the end of my journey to work?

[swinks]

yeah.. true.
Engine temp sensor?
That tapping was worrying. Maybe just loud tappets? Happens when oil fails due to cold weather. Then valves are not opening as should be.

[foxdie]

It wasn't the usual tappet noise, it was definitely more of a pronounced clang, it wasn't very loud but it was quite noticeable.

[Nutter_John]

water on the brake caliper froze the pad in place and it only released after moving ?

[foxdie]

Nope definitely engine related, it happened as I was backing upwards off the drive, and again when accelerating down the hill, no brakes in use at this point.

[c0xxy]

mine does that! feels like the handbrakes on, drive, clang n away i go! doesn't do it again tho until i next leave it

[funkstardelux]

same here. manual its the handbrake i found to be the course, but maybe something else as u say its in the engine bay.

[c0xxy]

mines from the front, but same clang as a handbrake free up. it is also sluggish until its drove for a few mins but i assumed that was cold oil in the autobox

[mike74]

Was the A/C on at the time?

[foxdie]

Was the A/C on at the time?

Yes it was

[miller]

I don't think that's it, if the cambelt had slipped a tooth, why would the car be back to normal and pull hard on boost near the end of my journey to work?

The car would drive fine even if the cambelt had slipped three teeth! Its just he idle that is noticeable, ie as if you had aftermarket cams in it.

[foxdie]

The car would drive fine even if the cambelt had slipped three teeth! Its just he idle that is noticeable, ie as if you had aftermarket cams in it.

The car was idling fine when warm, it was only whilst it was cold, is this likely to still be a slipped tooth?

[swinks]

Jason, how decent is coolant? Just got to work to cover one of shifts because my mate' s car broke down due to frozen coolant. It was water pump gone after rough start and loud tapping. So he' s unhappy chap and I'm checking for Astra water pump.

[foxdie]

Jason, how decent is coolant? Just got to work to cover one of shifts because my mate' s car broke down due to frozen coolant. It was water pump gone after rough start and loud tapping. So he' s unhappy chap and I'm checking for Astra water pump.

The coolant should be good, the car recently had a radiator crack and I replaced the radiator and coolant with this about 10 days ago; Halfords Ready Mixed Anti Freeze & Coolant 5 Litres

That's only a temporary situation until Nick Mann gives her a bloody good service this weekend.

[enigma]

Piston Broke - pull your front plugs and look for debris.