Smoking and blowback...

200ci66

200ci66

Well-known member
Well, two problems. I'm having problems with my car smoking after it gets warm. It's a white smoke (maybe blue, but not really) and is only exiting from the passenger side exhaust pipe. I DO have an exhaust leak here, but what's odd about it is that it's only smoking after my car has warmed up. A quick trip in and out of town, nothing. A trip across town after sitting at several stoplights, it's smokescreen all the way back to the house.

Another problem that I'm having is that my engine is blowing back right after I shut it off. It's a sucking sound in the carb that I assume is caused by excess gas. Is my car just running too rich? Both the smoking and the blowback started happening at the same time.

This started happening soon after I installed the 1968 distributor, and oddly enough my car has been running BETTER since I did this. It just starts smoking after a 20 minute drive, and there's a sucking sound 1 out of every 3 times you shut the engine off (again, this happens more after longer drives)
 
Where is the vacuum source for the distributor? What did you set the initial timing to be? If you used a timing light, are you certain the harmonic balancer hasn't slipped?

-ron
 
Vaccum source is on the distributor - check

I DID use a timing light, set the initial at 13-14 degrees - check

Pretty certain the harmonic balancer didn't slip

I'm not sure if the distributor has anything to do with it, and I wouldn't think an exhaust leak would cause a car to smoke only when warm as opposed to cold. Also, I added a quart of oil recently, and it's just a tad above the full mark on the dipstick (I've had it up this high before with no smoke, so I don't think it's too much oil).

Edit - After searching online some more, I've seen several people say that white smoke can be a sign of excess fuel burning, and if this is the case you will be able to smell it after you shut the engine off (and I can smell it) and on top of it all I HAVE had somewhat of a drop in fuel economy recently. Too much fuel? What are some ways to solve this?
 
White smoke is not a sign of excessive fuel burning, black smoke is. Blue smoke is oil burning, white smoke usually means water is getting into the combustion chamber, or condensation in the exhaust pipe when they are cold.
 
So, a blown head gasket maybe? Any easy way to check this? I know a loss of coolant is one way but I haven't really had any problems with this.
 
Exhaust will smell sweet if anti-freeze is leaking into cylinders. Black sooty residue in exhaust pipe is a sign of too rich, burning oil, blowby. Pull plugs, if one or more is sparkling clean, coolant is leaking into that cylinder. Make sure PCV is hooked up and working properly.
 
Definately isn't sweet smelling at all. I'll pull the plugs today and see what's up. Maybe it is the PCV.
 
The condition you refer to as 'running after shutting off the key' is called dieseling
http://en.wikipedia.org/wiki/Dieseling
Dieseling or engine run-on is a condition that can occur in spark plug, gasoline powered internal combustion engines, whereby the engine keeps running for a short period after being turned off, due to fuel igniting without a spark.
Click to expand...

Potential causes
Dieseling can occur for several reasons:

Built-up carbon in the ignition chamber can glow red after the engine is off, providing a mechanism for igniting unburnt fuel. Such a thing can happen when the engine runs very rich, depositing unspent fuel and particles on the pistons and valves. Similarly, rough metal regions within the piston chamber can cause this same problem, since they can glow red. It has also been suggested that an improperly rated spark plug can retain heat and cause the same problem.
A carburetor that does not completely close can contribute to running once the engine is off, since the extra fuel and oxygen mixture can combust easily in the warm piston chamber. Similarly, hot vaporized oil gases from the engine crankcase can provide ample fuel for dieseling.
Incorrect timing.
An engine that runs too hot or too lean may produce an environment conducive to allowing unspent fuel to burn.
An idle speed that is too fast can leave the engine with too much angular momentum upon shutdown, raising the chances that the engine can turn over and burn more fuel and lock itself into a cycle of continuous running.
Click to expand...

So this leaves you with trying to determine which of the causes you are fighting.. too rich, too lean, incorrect spark plug range, or just something in the cylinder that is getting too hot.

Pulling the plugs will tell you a lot. If they are dark and sooty, then you are probably too rich, if they are white, then they are either new, or too lean, if they are green tinted you are burning antifreeze, if you have a red tint (and running an automatic) your vacuum modulator may have gone bad and you are burning ATF (which also smokes white in color)

pull dem plugs!

And another way to test a head gasket is with a head gasket tester, sometimes if you have a fill funnel for your radiator you can fill it with fluid and when the motor is running it will constantly blow bubbles.

-ron
 
Pulled several of the plugs, and they were black. Cleaned them off, then turned in the screw to lean the mixture on the carb --- and lowered the idle thinking that would stop the dieseling. Filled the radiator up to a level that I can measure with a ruler, so I'll know if I have extreme loss for some reason.

I took it for a 20 minute drive today to get gas and cruise around. No smoke now. Last night it wasn't like I had a cloud behind me, but it was noticeable enough for me to think there was something wrong. Videos I've watched today of blown head gaskets send out a LOT more smoke than I thought they did. Didn't diesel back at all either, so maybe I have it right. Now I'll be running too lean...

If this starts up again I'll post in this thread again. Until then I think I'm going to let the thread die. Sort of a useless thread and I'm sorry, but thanks for educating me on dieseling, this isn't the first time I've had a problem with it and I'm glad I know what it is now.
 
To elaborate on CoupeBoy's post. That carbon buildup can cause deiseling by igniting the fuel. Pouring(drizzling not pour) a half can of Seafoam thru carb while running will clean most of it out. Pour the other half in fuel tank.
 
okay, drove it today and no dieseling. I think I got that problem taken care of.

However, after driving it again for about 45 minutes, it started smoking again! It's hard to say what color it is, but it definitely isn't black. Grayish blue? I think it's really odd that it only does this after the car has warmed up. It's running GREAT on top of it all. I haven't been loosing coolant, and my oil looks alright. I'm stumped.
 
Since you have dual out headers you can pinpoint which cylinders are the oil burning ones.
You can take it from there, but you have it narrowed down to 3 cylinders. Best of luck.
 
"...smoking after it gets warm..
the other occurrences that seem simultaneous might B coincidences (dizzy, etc) not causes. the length of time U mention 4 grey/blue ("but not really") smoke is the length of time it takes a motor to warm up. the "smoke color" indicates oil burn, the diagnosis of dieseling can support that.
 
I'll do a compression test today to see which cylinder it is. I assume it's a seal of some sort, because I'm actually running very well.
 
Glad to hear that part of the problem has been corrected. That smoking issue is a puzzle though. If it is a valve stem seal they can be changed easily with a spring compressor and a length of nylon rope.

Let us know what the compression test results are.
-ron
 
for compression testing that's a good thing, don't beat it your hed too much...
Just out of curiosity did you runa wet/dry test by warming up the engine test dry then add 1tbls oil and test to each cyl?

anyways it doesn't matter, your test shows consisant results for rings as is. (y) I think you just got lucky, pull the valve cover off and look at inbetween the valve springs for your valve stem seals, they look like umbrella's, if any are missing/broke you found your smoker!!! if not, then replace the 3 that smoke at the tail pipe.

the rope trick works great!

when oil gets warm is changes viscosoty and becomes more slippery per say, so it's more liquid like when it's warm or at temp which is why you see it after it warms up.

just think with the PSI the same in every cyl you don't have ring problems.
 
What's the way to test if it's the modulator valve? I've had quite a few people suggest that.

and no, no power brakes. no power steering either. And yeah, very true that at least I know my engine's still good from the compression test. Made me feel a little bit better.
 
To check the modulator get underneath and pull the hose off , if there is ATF there the modulator is leaking . There is frequently no noticeable function problem with a leaking modulator .
 
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