random puffs of thin white smoke at idle/slow speeds

[migoreng]

asked this Q on PA but replies are slow...
basically car runs great. no performance loss at all. it doens't blow any smoke at startup. car doesn't leak any oil on the ground.
using 10w40 magnatec.

i would drive for 15mins no problems and then slow down for lights or a corner.
a few secs later some white smoke would stay around in my rear view mirror. creeping the car/riding my clutch or reving slightly keeps producing slow thin white/greyish smoke until i take off...
then it won't happen again for another 15-20mins. car drives fine. i can hit vtec a couple of times...slow down and stop a couple of times..no problems at all til another 15-20mins

i slow down/stop for a corner...idle for a few secs and then the white smoke slowly comes out again...it actaully stays around longer than condensation...sorta looks like the trail of white smoke i leave behind with WOT acceleration til redline.

from reading around it's probably the pcv valve right? what do you people think? i've been wanting to give my car a full service for a while now but i just don't have time. i do bits and pieces every couple thousand kms..

basically what i have planned is timing belt and all that in a couple more months, change sparks cause i don't know the condition of em, fuel filter, tappet adjustments, brake fluid...and yeah i think that's it...

it's hell annoying seeing the light smoke behind every 15-20mins. the car is normal..no vibrations or anything. oil level is fine. coolant has been fine for the last 5000km.

other days it would probably happen only once every hour.
tonight it happened 4 times in the 40mins.

please explain
:wave:

cheers

[aaronng]

It's probably condensation since it is winter now. If it happens in summer, then look at the PCV. Also, if it is the PCV, you usually get more blue-white smoke when you use give it lots of throttle. But in your case, you use heavy throttle but no smoke.

[migoreng]

definately doesn't look like steam like i see in the mornings.
the smoke stays arond for a while.
><
if the smoke is starting and i creep the car/ride the clutch around then it will continue sorta...i don't know if it will go on and on but usually i'm already moving off after 5 seconds.
while cruising between 3000-4000rpm no smoke at all...

It's probably condensation since it is winter now. If it happens in summer, then look at the PCV. Also, if it is the PCV, you usually get more blue-white smoke when you use give it lots of throttle. But in your case, you use heavy throttle but no smoke.

drove for 1.5 hours (100+km) yesterday here and there...car should be fully warm. it happened as i slowed down for a roundabout, put it into second...turned the roundabout and left a trail of very thin white smoke ><

cheers for your replies...it's hard to find a mech that knows about hondas.
i ask some local ones and they don't seem to know about the common problems of hondas. they treat it like my car is an old camry or something lol

also like i said i do leave a trail of white/grey smoke when redlining 1st/2nd gear.

[aaronng]

Ahhh okok, well, try changing the PCV then.

[migoreng]

so i should be able to pick a valve up for $5-10 at a honda parts centre right?

also you know dyno runs..if a car is makes the right amount of power does that mean the rings,compression and all that kind of stuff is in good condition?

my car did 106.5kw... there weren't any other stock preludes around so i couldn't compare but corolla sportivos are pretty close and they were doing a few kw more than mine.

so do you think a compression test is really needed or not for my car?
cheers

[aaronng]

No, dyno results don't tell you your engine condition. I recommend you change the PCV first. Then after that if you are still gettign smoke, get the compression test done.

[Sp00ny]

so i should be able to pick a valve up for $5-10 at a honda parts centre right?


LOL! Wow you mustn't been involved with honda's for long! You'll soon learn that OEM parts cost a fortune, unfortunantly!

OEM PCV VALVE: $38 (from Memory)
Repco Branded: $12

User servicable parts like PCV Valves (simple parts that a differance in quality wouldnt make any major (if any at all) changes in your engines life/performance. Just buy aftermarket. Even if you change it every 30,000kms... which you could do but isnt by any means neccesary.

//------------------------------------------------------------

As for your smoke, I would at first change your PCV valve then go from there, however a PCV valve which has passed its service life shouldnt cause white smoke...it should cause a blue-ish smoke (as aaronng said) as when a PCV valve fails crankcase pressures rise and it causes blowback past the piston rings resulting in the burning of oil.

White smoke (provided it isnt condensation) is usually water/coolant. So monitor your coolant level closely. If no noticable changes are seen then try an ECU Diagnostic and see if it provides any error codes, then if no luck try a compression/leakdown test as aaronng suggested.

[migoreng]

if it was a compression problem would it smoke every single time i take off or idle?
what about valve steam seals?

cause i'm only getting puffs every 15-20mins...somtimes it may only happen 2 times an hour but depends if i'm starting and stopping a lot i think. i can't work out the pattern yet.
also how much is it for a compression/leak down and how long does it take? should any mechanic be able to do it?
some mechs are like nah you don't need one done because my car runs and idles fine to them...
it's like they don't want to help me out lol.
also my coolant and oil is fine.
checked it this morning in the freezing weather....oil is just over the top dot on the dipstick...coolant is still green. nothing weird looking at all

[Limbo]

maybe destructn can get us some discounted PCVs i know i want some spares

[Sp00ny]

if it was a compression problem would it smoke every single time i take off or idle?
what about valve steam seals?

cause i'm only getting puffs every 15-20mins...somtimes it may only happen 2 times an hour but depends if i'm starting and stopping a lot i think. i can't work out the pattern yet.
also how much is it for a compression/leak down and how long does it take? should any mechanic be able to do it?
some mechs are like nah you don't need one done because my car runs and idles fine to them...
it's like they don't want to help me out lol.
also my coolant and oil is fine.
checked it this morning in the freezing weather....oil is just over the top dot on the dipstick...coolant is still green. nothing weird looking at all

To be brutally honest, the best mechanic is the result of educating yourself. Truth be told i think my mechanic is great but only you are going to care about your car as much as you do.

The reason mechanics will drive you away from it is if they don't see any money in it, particulaly if it's a generic mechanic place like Mr. Muffler/Midas/Kmart T&A...etc These companies would rather do something that yields higher profit or will most likely result in follow up work...

//------------------------------------------------------------

If it was Valve Stem Seals it would be blue smoke similar with the PCV Valve which is why I am reluctant to suggest it has anything to do with oil burning, My closest guess...without seeing/driving/assessing the car would be water/coolant burning. Leaking/Cracked HG or a VERY unlikely event that a coolant channel in a Throttle Body/Manifold is leaking under low pressure mixing with the air/fuel mixture...which is honestly a shot in the dark.

We can't really help too much without seeing it and being there to assess it...even then with the aid of appropriate diagnostics we may not be able to conclude whats causing it...thus why some mechanics charge high to fix small issues as it may take them alot of trial and error to discover the issue.

If compression tests are below usual then one of the causes COULD be a cracked HG but....once again....the random time intervals are odd.

As mentioned earlier...i would change the pcv valve and perhaps ask a knowledgable mechanic of the possibilities.



also my coolant and oil is fine.
checked it this morning in the freezing weather....oil is just over the top dot on the dipstick...coolant is still green. nothing weird looking at all

Just because the coolant is Green doesnt mean its not in need of a change or top up...don't get fooled by coolant sitting in the top of the radiator due to pressure levels it can do this...yet the radiator could be half empty...if its Green chances are it wont change colour as it is a generic coolant...OEM Honda Coolant is Blue xD...Get some coolant if you dont already have some and top it up and see how much it takes ;)....

If all this fails, ask a knowledgable mechanic about the smoke...other than that there is not much else we can do...

Good Luck

[T-onedc2]

No, dyno results don't tell you your engine condition. I recommend you change the PCV first. Then after that if you are still gettign smoke, get the compression test done.
Az, is there a DIY for this? I'm noob at PCV

edit: is it the approx 2in long rubber tube at back of rocker cover on B18C?

[aaronng]

Az, is there a DIY for this? I'm noob at PCV

edit: is it the approx 2in long rubber tube at back of rocker cover on B18C?
The tube you are looking at is the breather hose. It just connects between the rocker cover and the intake arm. On the B18C, there should be a tube going from the intake manifold to the PCV and then onwards to the block. Something like this pic (supplied by ben). On some engines like mine, the PCV valve is actually screwed onto the block unlike in the pic where it is inline with the hose:
http://z.about.com/d/autorepair/1/0/-/P/accord_pcv_657b.gif

On other engines like the old SOHC F series, it is on the top of the rocker cover.

[T-onedc2]

^^^Thanks, great pic :thumbsup:

[migoreng]

after some more observations i noticed the puffs of smoke will happen after coming down a particular hill that i take everyday to work.
i will brake..downshift to third,then second, i expect the smoke to come out and what do you know?.. some thin white/greyish smoke comes out..lol ~10 metres after turning the corner a tiny bit of smoke will stick around behind but then it will stop...

i think i have read about this before? oil slushes around more after going up/down a hill.
i got to work, went up the first big speed hump and some smoke came out for a second or two but didn't happen at all on the next couple of speed humps.
lol

anyways gonna get the pcv and whatever done this weekend..gonna get a second opinion from another mechanic. i think i can trust him
when i was looking at a car last year he gave me a full car report...he noted heaps of thing stuff like cracked diff rubber mounts, engine mounts, he even said the chassis lined up properly so it hasn't been 'jumping' in high speed chases or anything..
he seems to be pretty good with his nose..he can smell oil in air filters and stuff like that :P

also this pressure thing with the pcv valve..how often does the engine activate the valve? like how would you make pressure build up faster in the engine? reason i ask is my smoke problem is intermittent...so i was thinking the pressure might be building up every 15mins, when it gets too high then that's when the smoke will come out?

cheers..

[Limbo]

valve is always on. It works on engine pressure buildup.
Just change the valve for the $ its cheaper than going to see a mechanic and wasting more time. If its not the PCV then go see the mechanic

[JohnL]

Assuming it actually is smoke:

Smoke from the exhaust when accelerating after the engines been on the overun in gear (i.e. accelerating just after slowing using engine 'braking' to slow the car), I'd normally tend to associate with worn guide seals and / or worn guides / valve stems.

If I'm on the right track with your problem, what I think might be happening is that on the overun there's a partial vaccuum in the exhaust, which 'sucks' crankcase gasses and oil into the exhaust pipe past the worn seals / guides / stems, which then burns in the pipe when you get back on the throttle pedal...(?)

[migoreng]

it's like someone sitting behind your car smoking a ciggie...it's that kind of visible smoke if you know what i mean.
it's not full white...

yeah i guess you're sorta on the right track...i'll slow down for a corner, downshift into second let go of the clutch, the syncro will rev up the engine and i will see the smoke behind come out for 2 seconds or so

but it doesn't happen all the time...that's the thing that puzzles me...
i'm probably just more paraniod now..i probably didn't see the smoke a few months ago..i would have concentrated on looking at the dashboard/road ahead when taking off...lol

now i tend to glance in the rear view more often after taking off just to see if the smoke comes out. i'm trying to work out a pattern...
i think if i engine brake while slowing down there's a higher chance of the smoke coming out..
also it will never happen in the first 10-15mins of driving.
my exhaust never puffs out anything visible when starting up in the mornings...(standing outside the car while turning the key then then walking to the back and looking at the exhaust pipe)
people say worn stems seals will cause oil to leak through overnight and burn when the car is started...
that's the thing that puzzles me as well..if my valve steam seals were worn heaps wouldn't i get a puff of smoke every morning because oil would have leaked into the cylinder?

anyways..will get a new pcv tomorrow and i will try and get a compression test done...
i pulled out my pcv and it makes a soft clicking but you gotta shake it pretty hard.
what should my engine be getting on the guage?

[JohnL]

It seems odd that the problem appears to be erratic, but it's probably hard to observe consistantly, as you say you do need to keep your eyes on the road! Sometimes the smoke might be there to some degree, but not rise high enough to easily see in the rearview, depending on how the air is flowing at the rear of the car??

Cold (thicker) oil may not pass so easily through the guides as it will when hot and less viscous, so the problem is less with a cold engine? When you shut down the hot motor, you lose the pressure differential between crankase pressure (positive pressure) and exhaust presure (fluctuating positive and negative), so even with hot oil, only what oil is already on the upper part of the valve stem will trickle down into the exhaust port, i.e. it isn't being 'sucked' through because of the pressure differential, so only a relatively minimal amount of oil may find it's way past the guides after shut down?

So, you might not get much smoke with cold oil because it doesn't flow as easily. You may not get much smoke on start up even if significant oil has leaked overnight into the port (which may or may not be the case) because the cold oil sticks to the cold port / exhaust pipe walls, and only burns away relatively slowly as the metal heats up, i.e. slow oil burn = less visible smoke with cold engine...

That's my best shot.

The engine may run perfect compression numbers but still be losing oil down the valve guides, so it's not really an indication.

To see if the smoke problem is associated with the PCV and the crankcase breathing system, you might try pulling the PCV out of the engine and fitting a temporary breather tube into the orifice (fed into a temp catch tank), so no blowby / oil can get into the combustion chambers). I'd also feed the induction pipe end of the breather intake pipe into the catch tank so you're venting out from two pipes. You'd still need the PCV to be working, so you could wrap it in some cloth (to act as a temp filter) and sit it in a catch tank (just to prevent it making any mess on the engine).

Hope this helps.

[migoreng]

compression test fine..
leak test fine..
new spark plugs now...

guess i've got nothing to worry about...i'll just have to get over this smoke then lol...
:)