Puff of smoke from exhaust on hard acceleration
01-21-2003, 10:01 AM
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Puff of smoke from exhaust on hard acceleration
Guys,
I've now noticed on two occasions a brief puff of smoke out of the exhaust on hard acceleration. In both cases it was semi-dark out so I'm not sure of color. In fact, it appears that it's headlights behind me that illuminate the smoke effectively. I'm pretty sure it's out of the tail pipe because I can clear see a vortex/swirl in the smoke cloud.
Anyway, my oil consumption is about 1 qt./1000 miles - I'm confident it's not an overfill or leaky valve cover gasket problem - and in an archive search I only found one reference to the puff of smoke from Graham Mitchell's post but no conclusive answers.
The car has 53k miles on it and is driven daily. But it's been a few months since my last DE so it's not been driven hard recently.
Could this be an early warning sign for exhaust valve guide failure? It doesn't seem to be a serious problem at this point and I carefully watch the oil consumption but it does have my curiosity going.
Thanks,
Ben
I've now noticed on two occasions a brief puff of smoke out of the exhaust on hard acceleration. In both cases it was semi-dark out so I'm not sure of color. In fact, it appears that it's headlights behind me that illuminate the smoke effectively. I'm pretty sure it's out of the tail pipe because I can clear see a vortex/swirl in the smoke cloud.
Anyway, my oil consumption is about 1 qt./1000 miles - I'm confident it's not an overfill or leaky valve cover gasket problem - and in an archive search I only found one reference to the puff of smoke from Graham Mitchell's post but no conclusive answers.
The car has 53k miles on it and is driven daily. But it's been a few months since my last DE so it's not been driven hard recently.
Could this be an early warning sign for exhaust valve guide failure? It doesn't seem to be a serious problem at this point and I carefully watch the oil consumption but it does have my curiosity going.
Thanks,
Ben
01-21-2003, 10:27 AM
#2
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That is very hard to diagnose from afar.
It could be unburnt fuel, or it could be whiffs of oil.
Further attention will need to be paid to the color of said smoke.
Gray or charcoal = Fuel
Blue tint = Oil
White (as in my avatar) = Condensation!
It could be unburnt fuel, or it could be whiffs of oil.
Further attention will need to be paid to the color of said smoke.
Gray or charcoal = Fuel
Blue tint = Oil
White (as in my avatar) = Condensation!
01-21-2003, 10:56 AM
#3
Rennlist Member
Ben,
It's not unusual for an engine's combustion chamber to "load up" with deposits if it's been subjected to a lot of city low speed driving and the typical lugging the engine.
My brother at one time had a (brand new) 1969 Camaro Z28 and after a few days of driving around town, the engine would "load up" with carbon, so that when you took it on the highway and punched it, great clouds of black soot and smoke would come out the two exhaust pipes. Quite a sight to see. Then it would be fine. The muscle car guys would call this "blowing the carbon off the valves" or an "Italian tune-up". Actually I tried to talk my way out of a speeding ticket once in my '69 Corvette by telling the trooper that I needed to blow the carbon off the valves and that's why I was doing 60 mph in a 30....
I imagine with the modern unleaded fuels and ignition systems, this "loading up" is less of a problem. Try an experiment - after a week or so of city driving, wind your car up and see what the smoke looks like in daylight. If it's even and the same color on both sides, and doesn't repeat the next run, then the engine was just loaded up a little bit. Gotta love those Italian tune-ups....
Mike Cap (Capocefalo)
1997 C2
ARena Red
It's not unusual for an engine's combustion chamber to "load up" with deposits if it's been subjected to a lot of city low speed driving and the typical lugging the engine.
My brother at one time had a (brand new) 1969 Camaro Z28 and after a few days of driving around town, the engine would "load up" with carbon, so that when you took it on the highway and punched it, great clouds of black soot and smoke would come out the two exhaust pipes. Quite a sight to see. Then it would be fine. The muscle car guys would call this "blowing the carbon off the valves" or an "Italian tune-up". Actually I tried to talk my way out of a speeding ticket once in my '69 Corvette by telling the trooper that I needed to blow the carbon off the valves and that's why I was doing 60 mph in a 30....
I imagine with the modern unleaded fuels and ignition systems, this "loading up" is less of a problem. Try an experiment - after a week or so of city driving, wind your car up and see what the smoke looks like in daylight. If it's even and the same color on both sides, and doesn't repeat the next run, then the engine was just loaded up a little bit. Gotta love those Italian tune-ups....
Mike Cap (Capocefalo)
1997 C2
ARena Red
01-21-2003, 11:38 AM
#5
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Not to worry you Ben, but....
What you describe is the classic 911 early sign of exhaust valve guide wear. 1qt/1000 miles is pretty good - but watch it very carefully.
It'll be interesting what you hear if you take it to a shop. I'll bet $ that most will tell you to rebuild the top end. I'm not sure about the 993, but almost all the pre 964 cars that I've delt with could have an exhaust valve job (including guides) without a top end rebuild (which would be unecessary at 53K miles) and without dropping the engine. Keep us posted!
sean
What you describe is the classic 911 early sign of exhaust valve guide wear. 1qt/1000 miles is pretty good - but watch it very carefully.
It'll be interesting what you hear if you take it to a shop. I'll bet $ that most will tell you to rebuild the top end. I'm not sure about the 993, but almost all the pre 964 cars that I've delt with could have an exhaust valve job (including guides) without a top end rebuild (which would be unecessary at 53K miles) and without dropping the engine. Keep us posted!
sean
01-21-2003, 11:59 AM
#6
Banned
Ben,
You referred to an earlier thread of mine. I doubt there is any connection. Mine turned out to be a faulty oil filter seal leaking oil, some of which burned and created puffs of smoke.
You referred to an earlier thread of mine. I doubt there is any connection. Mine turned out to be a faulty oil filter seal leaking oil, some of which burned and created puffs of smoke.
01-21-2003, 12:19 PM
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Ben,
It could be what Sean suggests but I'm more with Mike here.
Since it has been months without propes use (= hard driving) & you've been cruising around, especially if you have to sit in the traffic, when you finally 'let her rip', you can get dark smoke.
I'd suggest you check first what color the smoke is (have someone driving behind you) and if it's dark, take a good & loong spirited driving & check again.
It could be what Sean suggests but I'm more with Mike here.
Since it has been months without propes use (= hard driving) & you've been cruising around, especially if you have to sit in the traffic, when you finally 'let her rip', you can get dark smoke.
I'd suggest you check first what color the smoke is (have someone driving behind you) and if it's dark, take a good & loong spirited driving & check again.
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01-21-2003, 02:12 PM
#8
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My prior '87 had worn valve guides at 116K. Consumption was 1qt/1,000 when small puffs started, then finally 1qt/400 with big clouds. Initial puffs and later clouds occurred on acceleration every time, not occasionally. I did the top end rebuild. On 993, most of us "senior mileage club" members are getting about 1qt/2,000 miles. I am getting 1qt/2500. I would do the Techron bottle and vigorous drive blowout, and hope for the best.
01-21-2003, 06:39 PM
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Was your operating temp up when you got into the throttle? I stomped it to pass a careless driver on a cold engine one night and left a dark cloud about 100 feet long. No other signs of problem--normal oil consumption and all.
01-21-2003, 08:48 PM
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Guys,
Thanks for your replies:
Mike B - I realize I need further analysis - but I was wondering if those you had valve guide wear saw early symptoms like mine. When I have more definitive info I'll post again.
Mike Cap, Kevin, FF - I agree - in fact I'm hoping that's the case. I have a Time Trial School coming soon (if they let me in) and a DE in Feb. so we'll see if that clears it up.
Chris C - Engine was at temp both times. I try to stay below 4k rpm until oil temps are up - except in grave emergency like when one of the super-sized SUV's doesn't see me in a lane change because my roofline is below their mirrors!
Graham - I thought as much but I had to PROVE that I did an archive search before asking about an oil puff <img border="0" title="" alt="[Wink]" src="wink.gif" />
Sean and Terry - If it turns out to be the valve guides the worst part will be p-car withdrawal for a couple of weeks. I purchased an extended warranty when I bought the car for just such eventualities.
I'll update if/when I find out more!
Ben
Thanks for your replies:
Mike B - I realize I need further analysis - but I was wondering if those you had valve guide wear saw early symptoms like mine. When I have more definitive info I'll post again.
Mike Cap, Kevin, FF - I agree - in fact I'm hoping that's the case. I have a Time Trial School coming soon (if they let me in) and a DE in Feb. so we'll see if that clears it up.
Chris C - Engine was at temp both times. I try to stay below 4k rpm until oil temps are up - except in grave emergency like when one of the super-sized SUV's doesn't see me in a lane change because my roofline is below their mirrors!
Graham - I thought as much but I had to PROVE that I did an archive search before asking about an oil puff <img border="0" title="" alt="[Wink]" src="wink.gif" />
Sean and Terry - If it turns out to be the valve guides the worst part will be p-car withdrawal for a couple of weeks. I purchased an extended warranty when I bought the car for just such eventualities.
I'll update if/when I find out more!
Ben
01-21-2003, 11:17 PM
#11
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</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Originally posted by Ben in Plano, TX:
<strong>Mike Cap, Kevin, FF - I agree - in fact I'm hoping that's the case. I have a Time Trial School coming soon (if they let me in) and a DE in Feb. so we'll see if that clears it up...
I'll update if/when I find out more!
Ben</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Yep, let us know. Hopefully DE's etc. will clear it out!
If it doesn't, at least you have fun trying! <img border="0" title="" alt="[Wink]" src="wink.gif" />
<strong>Mike Cap, Kevin, FF - I agree - in fact I'm hoping that's the case. I have a Time Trial School coming soon (if they let me in) and a DE in Feb. so we'll see if that clears it up...
I'll update if/when I find out more!
Ben</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">Yep, let us know. Hopefully DE's etc. will clear it out!
If it doesn't, at least you have fun trying! <img border="0" title="" alt="[Wink]" src="wink.gif" />
