Troubleshooting

[ajgriffin]

So my truck recently went from running fine to running like crap and sometimes throwing black smoke out of the drivers tailpipe. It also sounds like there's a miss or something going on when the truck is running. Any ideas what may be going on? Here is a picture that may have some breadcrumbs in it. Notice what appears to be oil coming from the tailpipe on the ground

[Shyguy]

Pull the spark plugs and see what they look like. If any of them are oil fouled you will have a better idea what is going on. Also do a compression check.

[Lee H]

How old is the tune up, not just the look over and assume all's well but a real tune up? Plugs, wires, points if still there, carb rebuild, timing. I would do a compression test, then a leak down. Those tests would tell you what to do next, could be just a real tune up, maybe some valve seals, or if engine work is needed.
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[MacGyver72]

Black smoke usually indicates carbon build up either in the cylinders or in the carb. This is usually caused by running rich. Blue smoke is burning oil usually from leaking valve guides. The leak down will indicate if you have either an issue with rings or with a valve not completely sealing.

Best bet are your plugs, cap and rotor. A complete tune up like Lee suggested will more than likely solve your problem.

[ajgriffin]

Thanks for the suggestions so far. Can you guys explain how to do a compression or leak down test? I just changed the plugs two nights ago. I attached a pic of one of the old ones, all of them looked like this.
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[cdowns]

do you have cheap chrome valve covers withPVC valve installed without baffels?

[ajgriffin]

I can't say for sure. They don't look to be anything special, but there is a baffle at the oil filler cap. I'll pull them tonight to see.
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[MacGyver72]

Plugs look good. Cap, rotor, and wires would be the next items to check. Check the routing of your wires. Often they are too close to the exhaust to last very long. You might also replace your fuel filter. Your issue could be one of fuel delivery.

[CC69Rat]

Originally Posted by MacGyver72

Plugs look good. Cap, rotor, and wires would be the next items to check. Check the routing of your wires. Often they are too close to the exhaust to last very long. You might also replace your fuel filter. Your issue could be one of fuel delivery.

I agree - sounds like it's hitting on 7 cyls. Is the plug in the picture your old plug? Did the problem begin after you changed the plugs or did you change the plugs to try to correct / troubleshoot (?) Did you put the same type plug back in it? you may have a colder heat range plug causing the miss.

Does it have headers on it? Check your plug wire boots. You might have one too close and when the plug fires, it arcs over to the header pipe instead of going to the spark plug, causing that cyl to drop out. = firing on 7. I had a 406 in an old Firebird a long time ago and it was bad to burn through plug boots. .. just some things to try. An easy way to check is to raise the hood at night. At times you can see the arcing as it happens.

Looks like a rich condition, that cyl is not firing and burning the gas causing the black smokey stuff to blow out.

.. just my .02.
Chad