Very odd ... one off smoke on start up ... for a few seconds ???

[Submariner1]

car has not been run for 3 or 4 days ... started her ( engine revs seemed a little fast ) looked back and saw smoke coming up over the boot?

Normally she is totally smokeless on start up during running.

Reved it to 1500 rpm twice ( 2 blips and the smoke was gone!
Tried revving and starting .. totally smokeless.

Checked the oil ... possibly lost 0.5mm to max 1mm in a year, but maybe not even that.

Engine sounds fine .. went for a drive ... ran perfectly , no smoke on startup or once hot, under harsh acceleration.

Tried starting her 10 times no smoke, let her go stone cold ... started her. .. no smoke.

So what's that about ??

Only things I could think of are
1. The car was left jacked up at the rear and water may have dripped into the exhaust, but the smoke was too quick ... she would have been too cold.
2. Did I accidentally press the accelerator ( before starting her ) when I climbed in? Highly likely as I was dirty after being on the floor p, so I had a towel on the seat and was concentrating not to move that as I slid in.
3. Some odd computer mixture glitch??

Now tried starting her at least 15 times no smoke, reved and reved her still no smoke and sounds perfect
Doing the normal 26 mpg in traffic.

Not worried but interested what could cause that?

 

[bob 6600]

What colour smoke? Water vapour?

 

[Ken_R]

Mine does it, some weeks, once or times a week. Other weeks, nothing. It's been doing it for the two years that I have owned it. No noticeable oil usage. I'm assuming just a little seepage somewhere.

 

[Submariner1]

What colour smoke? Water vapour?

I know it sounds crazy but not sure if it was white or grey, it was over so quickly it didnt register.
Just got back from a reasonably fast drive no smoke on start up when she was cold, or on the return or during accelerating. Sounds just like normsl driving and at idle.

Water Temp runs at the normal 85 to 90 ... well where she normally resides a few mm over 80C
Gave it some serious accelleration .. all normsl went like a rocket, pulled really hard.

Makes one feel like it didnt happen.

 

[Submariner1]

Mine does it, some weeks, once or times a week. Other weeks, nothing. It's been doing it for the two years that I have owned it. No noticeable oil usage. I'm assuming just a little seepage somewhere.

Wierd, maybe it got the mixture wrong for a second or two?
I suppose as it was just once in 2 weeks short of a year I will forget it.
During the 3 days doing the level sensors I did just start her after each one, to check no error messages, maybe she was a little flooded on the fist start up?

 

[Submariner1]

What a nerd, just realised when I was constantly spraying the silicone spray ( to work it into the ball joints) a fair bit got on the exhaust. I didnt bother wipe it off!
Maybe that was smoking, but would it happen so quickly ??

 

[stwat]

Have you never heard of condensation, evaporation?

 

[Submariner1]

Have you never heard of condensation, evaporation?

Could that happen in 15 seconds hmmmmm

 

[LostKiwi]

Wierd, maybe it got the mixture wrong for a second or two?
I suppose as it was just once in 2 weeks short of a year I will forget it.
During the 3 days doing the level sensors I did just start her after each one, to check no error messages, maybe she was a little flooded on the fist start up?

Mixture would be black or blue (if it washed a little oil off the bores).
Its also unlikely to get it wrong as the fuel at startup is open loop (determined by the map using data provided by the inlet air temp sensor, MAF, and coolant temperature sensors. As the engine warms up the ECU goes to closed loop and calculates mixture from feedback from the Lambda sensor. There are pretty much only four times the ECU runs in open loop - startup (hot or cold), wide open throttle, EML on (if a Lambda fails for example) and limp mode.
I'm going to guess it was condensation from water in the exhaust.

 

[flowrider]

Its the time of year, condensation blowing out on start up, no need to worry about every little thing.

 

[Submariner1]

Mixture would be black or blue (if it washed a little oil off the bores).
Its also unlikely to get it wrong as the fuel at startup is open loop (determined by the map using data provided by the inlet air temp sensor, MAF, and coolant temperature sensors. As the engine warms up the ECU goes to closed loop and calculates mixture from feedback from the Lambda sensor. There are pretty much only four times the ECU runs in open loop - startup (hot or cold), wide open throttle, EML on (if a Lambda fails for example) and limp mode.
I'm going to guess it was condensation from water in the exhaust.

Thanks,

I think you are right, it must have been condensation in the exhaust, its been pouring with rain periodically for the 4 days the car was not used, and very humid. First time this summer I have seen condensation on the windows (the last two cold nights). Plus pretty sure when jacked up at the back, some water runs off the bumper into the exhaust tips.

Racked my brains and I think it was probably white smoke. Not sure what that indicates? But think its water in the engine.

Anyway got the wife to start her up this morning. Not a trace of smoke ... absolutely clear

Checked these:-
Oil Dipstick ... no loss of oil, only clear oil on it .. no trace of water or milkiness.
Opened Oil filler cap ...... totally clean oil ... no milky crap whatsoever
Checked Coolant ... totally full ... clean water , no trace of oil (i.e. blueish swirls, colours etc.like you see in a puddle if oil on dropped on it).
Went for a little drive from cold around the village ... all perfect and saw 25.2mpg ... which is its normal. and IMO pretty dam good for a 5.5L, huge, heavy car in urban from cold.

As its the first 2nd hand car for me in 28 years, I guess I watch it like a hawk because I didnt baby it from new.
Thankfully the original owner wasn't a boy racer type, and one benefit of a 5.5L engine is I guess you really have to be going totally nuts to abuse it.
Even if you try to get her really going, one comes across traffic holdups so quickly; and well before you are getting close to even slightly stressing that engine.

 

[LostKiwi]

Racked my brains and I think it was probably white smoke. Not sure what that indicates? But think its water in the engine.

Only rarely.
Usually its either water vapour in the exhaust (water is a by product of combustion) condensing when hitting colder air, or its water in the exhaust being converted to steam by heat in the exhaust as the gases flow over it.

 

[Submariner1]

Only rarely.
Usually its either water vapour in the exhaust (water is a by product of combustion) condensing when hitting colder air, or its water in the exhaust being converted to steam by heat in the exhaust as the gases flow over it.

Thanks useful to know.
Its definitely water vapour.
I Just got caught in the rain applying a second coat of anti rust to the suspension nuts ( with the car jacked up at the rear) .
ooops water runs off the bumper and drips "into" the exhaust tips!

Covered them with clingfilm to stop any more going in.
In the normal position it drops off in front of the tips. Tilted up, and its directly under the fall of water dropping off.

Once finished, its off for a decent fast run to quickly evaporate it all off.

 

[Submariner1]

Its the time of year, condensation blowing out on start up, no need to worry about every little thing.

Never seen it before ... including all last winter.
Seemed sensible to ask, especially after reading Alexs post which required a new engine ( which wouldnt be a little thing would it? ) .

Anyway definitely discovered why it happened .... when it started to rain just now ... jacked up at the rear, puts the exhaust tips directly under the run off from the bumper

Covered them to stop any more going in.

 

[LostKiwi]

A little water down the exhaust will do no harm. A couple of gallons maybe but not bumper run off.
The exhaust is subjected to water and acid products from combustion anyway.

 

[Submariner1]

A little water down the exhaust will do no harm. A couple of gallons maybe but not bumper run off.
The exhaust is subjected to water and acid products from combustion anyway.

Thanks and True, especially as CLs have fully stainless exhausts.

One thing I learnt ... I wouldnt leave her jacked up at the back overnight .. without covering the tips.
Just in case we had a sustained down pour.