RE: IML: Black smoke out exhaust

[RandalPark@xxxxxxx]

If you open the air cleaner lid while the engine is warm, and see that the choke is OPEN, then your carburator probably has failed. 

The black smoke is nearly always (frankly I can't think of any other reason) from buring too much gas and not enough air, making a "rich" mixture. The purpose of the carb is to provide the correct mixture of air and gas for proper combustion. 

The choke must be closed to start the cold engine, but must also open as the engine warms up, to have the correct mix of gasoline and air under all conditions. Your car may have a choke pull off that is vacuum powered. Sometimes these fail and will cause the choke to close partially, resulting in some black smoke. The pull of can be easily tested and if necessary, easliy replaced. The choke should also have a thermal acting mechanism, either utilizing engine heat, or an electric heating coil to open the choke during warm up. If these don't work properly, a rich fuel mixture after warm up results and causes a lot of black smoke. 

If the choke is working properly and you are experiencing black smoke (a lot or a little), than your carb is dumping too much gas into the engine. There are many other things that can make the car run the way that you describe, but not very many (if any) that are accompanied by the black smoke. It may be possible to fix the carb, but it should probably be either rebuilt of replaced.

Once you have gotten to the bottom of this, you should also replace your spark plugs. If they haven't fouled out already, they probably soon will. On modern cars, when this happens, the catalytic converter MUST also be replaced. It will plug up in 10 miles and be beyond repair.

Paul W.

In an email dated 17/6/2005 6:26:37 pm GMT Daylight time, "Ken Lang" <ken@xxxxxxxxxxxxx> writes:

>Yep, sounds like a stuck choke to me.
>
> 
>
>Ken
>
>'67 Crown
>
> 
>
> ?_____ ?
>
>From: mailing-list-owner@xxxxxxxxxxxxxxxx
>[mailto:mailing-list-owner@xxxxxxxxxxxxxxxx] On Behalf Of Greg Graham
>Sent: Friday, June 17, 2005 9:26 AM
>To: mailing-list@xxxxxxxxxxxxxxxx
>Subject: IML: Black smoke out exhaust
>
> 
>
>My '67 Convertible just developed a strange problem. ?It has run fine,
>absolutely wonderful, for days. ?I drove it to work this morning and it
>performed perfectly. ?I had to run an errand at lunch and went out to start
>the car. ?It started fine, but the exhaust sounded ever so slightly
>"muffled". ?Idle was fine, so I put it in gear and went on my way.
>Acceleraton didn't feel right, it was as if I was pulling a trailer. ?I
>stopped at a stop sign and then pressed the gas to go and a big plume of
>black smoke came out of the tail pile. ?I let off the gas and noticed that a
>slight trail of back smoke continued. ?The further on the pedal that I
>pressed down, the more smoke I got.. and now the performance went downhill
>fast. ?I had to press the pedal down twice as far as usual, resulting in
>black smoke just to drive 35 mph. ?I had only driven 2 miles from work and
>now could barely top 25 mph with the pedal nearly to the floor... black
>smoke just gushing out the back end. ?I pulled over and put the car in park.
>Black smoke dropped to almost nothing and I peaked under the hood. ?The
>engine was idling perfectly. ?Smooth and no misses whatsoever. ?I blipped
>the throttle cable and the engine revved smoothly, but more black smoke out
>the tailpipe. ?
>
>So, the engine seems to be running fine, but black smoke gets worse as I
>accellerate. Car seems to have no power while in drive. ?Engine revs and
>transmission does not slip. ?I backed the car up into a parking spot and
>scratched my head a bit. ?Walked around to the back end of the car and the
>exhaust does sound a bit muffled still. ?It also left a black patch on the
>grass just while idling. ?I rubbed the grass between my fingers and it was
>sooty, no real fuel smell. No grey smoke, no steam, so probably not rings or
>a head gasket. ?What on earth is going on here? ?My guess was a clogged
>exhaust, but then it probably would have blown that sucker right off the car
>when I revved it a couple of times, now wouldn't it? ?Could it be a pvc
>valve? ?Does the '67 440 ?have a pvc valve? ?HELP! Thanks.
>
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