ViribusUnits

Right after start up, sometimes my 928 makes clouds of white smoke.

On closer inspection, is it deffently gasoline, not water.

After running for a minute or so, something changes, the idle picks up, and the exaust cleans up. No white smoke, no gasoline smell.

It's like an on and off deal.

My cold start injector is not hooked up. If it was leaking, I wouldn't expect it to correct it's self in under a minute.

I'm stumped as to what could cause such a problem. My next guess is that I have a leaking cold start injector, and after a few seconds, the O2 sensor heats up, and leans out the mixture. Heck if I know if thats even possible!

Thanks.

Weissach

White smoke is oil. Black smoke is gas.

ViribusUnits

Well, that leaves me even more confused.

Why did it clear up in a short peroid of time?

Why the strong smell of gasoline?

Thanks.

rjtw

White smoke can also be coolant.

VB, are you sure it's gasoline smell, and not burning oil smell?

Has the car recently overheated?

Whether it's oil or coolant, it sounds like this *could* be a leaky head gasket or cracked cylinder head. I've had both happen (on other cars, not yet on the 928).

Here are some things to look for:
- Check your oil. If you have water in the oil (often a byproduct of a cracked head) you'll need to fix the problem asap, at risk of engine damage from improper lubrication. Water, if present, should be apparent on the dipstick.

- Are you losing small amounts of coolant for no apparent reason? It could be ending up in one or more cylinders. It might take a week or more to become obvious. That's pretty typical of a small leak (could be either the gasket or a head) that, under pressure of the cooling system, slowly leaks in to a cylinder. It might actually leak in almost all the time and get burned off unnoticeably. It's also possible that heat expansion temporarily fixes the leak, for now. But, when the car sits overnight after being run, residual pressure in the system forces a larger amount of water to collect that takes a while to fully burn out.

- One test to identify the problem cylinder(s) would be to start the car in the morning and only let it run for a few moments. Then stop it and pull out spark plugs, looking for signs of either water or oil on the plug. (If it's oil leaking into a cylinder, pulling the plug anytime should reveal oil fouling).

I'm sure other folks will have lots of sage advice too.

One thing I can say for sure is that it's not a cold start valve issue -- like Weissach says, excessive gas makes black smoke.

In fact, the gasoline smell is consistent with a cold engine. If it's just gasoline you're smelling, then it must be coolant causing the white smoke.

I hope I'm wrong on this, VB -- but at least check for water in the oil, I'd hate to see your engine get damaged!!

Good luck!!
Rick

Cobey

This is probably a silly question to some of you, but what exactly is he looking for to see if there is water in the oil? Something akin to mixed up italian salad dressing?

Chucker

I have a question now that VB opened the door. My car at start up gives off well... not white or black smoke, but you can see the exhaust (condensation?). This lasts for one minute and then goes away. Everytime the same thing. Do other 928 owners have this same thing happen on start up?

rjtw

Cobey -- Italian salad dressing is it. Or just a few slimy gobs of clear stuff (water) hanging out near the top of the dipstick.

Chucker -- Good point, maybe it's just condensation! Yes, a few whisps of condensation right after starting when it's cold outside is perfectly normal. (But not "clouds" of it like VB has, and not during warm weather either).

Cobey

Thanks rjtw!

BrianG

Another possibility that you are not going to like is that white smoke could be coolant. It has the characteristic sweet, antifreeze smell, if that's your coolant. The "rad guys" have some stuff they can put in the rad to "tell-tale" the coolant smoke. Also, they can pressurize the coolant system and watch for leakdown to confirm the existence of head gasket or cracked head.

As for the explanation of rapid clearing of oil-smoke, that is characteristic of early exhaust valve guide seal leakage. What happens is that the hot oil runs past the valve seal soon after shutdown. It accumulates on the valve and maybe even drips onto the piston. On light-up, the oil is rapidly burnt off and there is positive pressure while the engine is running, so the oil doesn't get by the seals. An accurate test for this condition is to find a nice long hill and get going pretty good as you approach the hill, from the top. Upon descent, let off the gas for a good few seconds (like 10). This high vacuum condition will suck oil past the leaky seals. Watch behind as you step back into the throttle near the bottom of the hill. A puff of smoke confirms the condition.

V-Fib

Check your oil strainer and breather hoses not just the dipstick. If it's coolant, you'll know immediately. If it is coolant, it can come from failed headgaskets or oil cooler in the radiator. I had no oil cooler so I pulled the heads and #7 cylinder had coolant in it. I had the same symptoms as you are describing. Lots of WYAIT's if you have to pull the heads. I hope you don't have headgasket problems. Let us know what you find.

Anthony Tate
79/928 Silver Metallic

ViribusUnits

I just went out and double checked.

I haven't lost any coolent. There isn't an oil slick on the coolent.
good news there.

I'm not sure if it's eaten any oil. Up untill here recently, I've had a pretty good oil leak. One from a defunct cork seal on the strainer, and one from lose bolts on the passaner's side of the oil pan. It put quite a bit of oil on the ground. I've fixed the two leaks, so I've been drop free for the last two weeks. I've added a little under a quart in the last 8,000 miles. It's time to change the oil, gonna happen this weekend. There is no water in the oil. Good news there.

As long as I've owned the car, she has never overheated.

I was sure it was gasoline, and white, but now I'm not sure. It's not a cloud per say. It's enough that you can see there is something there, but it's hard to make out a color. I'm pretty sure it's not black, but eighter grey or white. It smells like gasoline, or maybe burnt oil. When I'm there, it smells like gasoline, but after I left, my hair smelt like it had been around an oil fire. Don't ask me how I know how that smells. ;-) I smell pretty bad right now.

I did notice something disterbing. While checking out the exaust, I placed my hand infrount of the tail pipe, and noticed a slight drop in the flow ever so often. Uh oh, looks like there is a intermitent miss in the thing. It'll not happen for several seconds on end, and then there will be make 1 to 3 of them, and then it clears up for a while. Hopefuly it'll clear up when I get the ignition problems figured out. If not, maybe when I get the smoke thing figured out.

From what Brian says, looks like I'm in for a top end rebuild in the not too distant future.

WallyP

Pull the vacuum lines that go to the fuel pressure regulator and dampeners, and check for any trace of fuel in the lines. Replace any leaking unit.

A leaking injector will leak fuel into the manifold that will be burned upon startup. Hard to tell which one.

tresamore

Fuel smoke can be grayish white if there isn't alot of fuel burning and it is mixed with the condensation of a cold start. The injectors could be dripping into the cylinders and puddling on top of closed valves after the car is off. This will then be burned in the cylinders and cat after the next start, hence the stumble until it clears. The O2 sensor is trying to lean the motor but the fuel is already out of the cylinders. Then when its all gone you are back in business. Try adding a fuel pressure gauge and watch it after the car is off. If you have no other fuel system problems it should hold pressure. Of course this is just a thought, a loong thought. Good luck!

ViribusUnits

Tesamore.

I like fuel issues. Much cheaper than valve issues! (at least I don't have to pull the heads!!!)

Question, will only the main injectores do it, or will the cold start injector do that same thing? I've yet to test it properly, but I've gotten several indications that my cold start injector is leaking.

The last time I checked it, I belive the fuel rail held pressure. I didn't specificly check that though, so I'll take another look at it.

tresamore

Sure it could. I pretty sure its pressurized all the time with the rest of the injectors. Anything pressurized w/ fuel could do it. Heck, I think even the pressure reg diaphrams can leak into the vac system and dump fuel into the intake that way, if they're bad. Man I gotta get to bed! Check ya tomorrow AM.
<img border="0" alt="[byebye]" title="" src="graemlins/wave.gif" /> <img border="0" alt="[sleep]" title="" src="graemlins/sleep.gif" />