puff of smoke when changing gears

RG.net · Postby **RG.net** » Sat Feb 23, 2008 3:39 pm

i noticed when i change gears at high revs (6-7000rpm) in hold mode on my auto nb8a, a white puff of smoke comes out the exhaust, it also does it in auto mode, any ideas, i was thinking something like dead fuel but i'm not 100% on it.

thanks.

JBT · Postby **JBT** » Sat Feb 23, 2008 3:40 pm

What colour smoke? Is the engine using any oil?

Alex · Postby **Alex** » Sat Feb 23, 2008 7:39 pm

not sure but it seems to be an issue that affects most cars, or at least the one's I follow sometimes, only on near redline changes, I guess it has something to do with it getting rich as the load is reduced between gears

but then I don't know that much about cars so I'll leave a proper analysis to the pro's

RG.net · Postby **RG.net** » Sun Feb 24, 2008 2:50 pm

jbt, the smoke is white, at one stage it was drinking oil, but it has stopped, i did put stop smoke in the engine about a month ago, so maybe that has sealed up thickened up the oil enough for it not to leak out.

JBT · Postby **JBT** » Sun Feb 24, 2008 6:11 pm

Hmmm...white smoke generally means water in the combustion/exhaust cycles (head gasket, cracked head etc.).

Blue smoke = oil and black = fuel.

Might be worth getting a coolant pressure test carried out to see if that shows up anything.

RG.net · Postby **RG.net** » Mon Feb 25, 2008 10:59 pm

thanks jbt.

i have noticed my 5 consuming almost double the amount of petrol then it normally does.

its starting to drink oil again, but there was no blue smoke, it was white.

the ammount of coolent has not changed since i installed my cooling pro radiator.

i might get a compression test done. other then that i dont really know what else to do, my mechanic said it was normal when this started and suggested that it could be the valve stem seals, anyone encountered this problem before?

bigdog · Postby **bigdog** » Mon Feb 25, 2008 11:08 pm

You may be seeing unburnt fuel Croc.

I had never experienced this till last week - my son has a newly bought Hilux ute on LPG. The previous owner hadn't run it on petrol for some time, so muggins here pops $20 worth of unleaded in and hits the fuel switch. Nothing. No go. OK says I, fuel system has been disabled. A few days later we are driving along and it starts to miss, and the as it dies it catches again and runs fine, but we have left behind the mother of all smoke clouds - pure white. This happened several times on the trip straight to the mechanic who quickly diagnosed that the fuel switch was allowing gas and petrol into the carby at the same. The float has a hole in it so the fuel is flooding the carby and the combination was causing the clouds of smoke. Problem solved by permanently disconnecting the petrol lines in our case... but in yours I'd be checking the fuel system.

JBT · Postby **JBT** » Tue Feb 26, 2008 8:27 am

Crocaine wrote:i have noticed my 5 consuming almost double the amount of petrol then it normally does.

Aaah, a vital piece of information. As I said white smoike generally means water. Armed with the extra info, I'm also inclined towards a fuel problem (dodgy injector or something).

RG.net · Postby **RG.net** » Wed Feb 27, 2008 5:51 pm

mmm i'm guna check that out, any ideas on the sudden loss of oil? i did have a leak before which was a broken underdrive pully seal and that has been fixed some time ago.

thanks for your help jbt and bigdog, btw i'm still loving these seats

stevesports · Postby **stevesports** » Wed Feb 27, 2008 6:17 pm

Crocaine wrote:thanks jbt.

i have noticed my 5 consuming almost double the amount of petrol then it normally does.

its starting to drink oil again, but there was no blue smoke, it was white.

the ammount of coolent has not changed since i installed my cooling pro radiator.

i might get a compression test done. other then that i dont really know what else to do, my mechanic said it was normal when this started and suggested that it could be the valve stem seals, anyone encountered this problem before?

sounds like valve stem seals. I know my mechanically minded mate said this to one particular car we looked at.

at startup it puffed a slight bit of white smoke. Also the oil smelt like the valve stem seals were gone (don't ask me what they smell like, mate smelt it).

JBT · Postby **JBT** » Wed Feb 27, 2008 6:17 pm

Are there any oil leaks? How much oil is it using?

RG.net · Postby **RG.net** » Fri Feb 29, 2008 12:26 am

no oil leaks that i can find, chews almost if not all the oil i put in, in a week or 2. i was also told it was the valve seals not being lubed enough and going hard, no puff on start up though.

JBT · Postby **JBT** » Fri Feb 29, 2008 8:10 am

Worn valve seals normally cause a puff of smoke after start up or during acceleration after prolonged idling.

If your car is chewing that much oil (\"chews almost if not all the oil i put in, in a week or 2\"), I think you have very worn rings/internals. Time for a compression check.

A friend up here had similar symptoms with an NB8A i.e. high fuel and oil consumption and the occasional puff of smoke. Engine was stuffed. Her car goes great now with a used engine from MX-5 Plus.

RG.net · Postby **RG.net** » Sat Mar 01, 2008 7:26 pm

the fuel has gone back to normal now, don't know why, but last 2 fill ups resulted in 100kms less out of a tank, now its about right with 181kms on half.

will have to check it out, thanks for your help