Troubleshooting - The 1947 - Present Chevrolet & GMC Truck Message Board Network

ajgriffin · 10-06-2011, 02:17 AM

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 · 10-06-2011, 09:21 AM

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 · 10-06-2011, 10:19 AM

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 · 10-06-2011, 10:24 AM

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 · 10-06-2011, 11:10 AM

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 · 10-06-2011, 12:33 PM

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

ajgriffin · 10-06-2011, 01:28 PM

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 · 10-06-2011, 03:17 PM

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.

10-06-2011, 02:17 AM	#1
ajgriffin Registered User Join Date: Feb 2008 Location: Carson, CA Posts: 581	Troubleshooting 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 Attached Images __________________ 69 C10 SWB -- Left to me by a loving father. Finishing the build we never got the chance to do together

10-06-2011, 09:21 AM	#2
Shyguy Junior Member Join Date: Dec 2006 Location: Southeast Missouri Posts: 2,436	Re: Troubleshooting 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. __________________ '67 Chevy C-20 short stepper - build complete, 454/SM-465. '75 C-30 Single Cab DRW-350 small block/NP-435. '77 GMC-6500 Dump Truck, 427 Tall Deck. '92 GMC K-3500 Duallie, 454/4L80E.

10-06-2011, 10:19 AM	#3
Lee H Registered User Join Date: Jun 2010 Location: Upland Ca Posts: 4,143	Re: Troubleshooting 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. Posted via Mobile Device __________________ 1972 C10 SWB, Air, PS, PB, 350/350THM. Second owner. 1965 Corvette roadster, 44K miles, 327/365 SHP, 4 speed, side exhaust, knockoffs, teak, second owner (bought in 1970), Have ALL numbers matching components. My frame off restoration thread: http://67-72chevytrucks.com/vboard/s...d.php?t=556703

10-06-2011, 10:24 AM	#4
MacGyver72 Registered User Join Date: Sep 2011 Location: Greencastle, IN Posts: 132	Re: Troubleshooting 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.

10-06-2011, 11:10 AM	#5
ajgriffin Registered User Join Date: Feb 2008 Location: Carson, CA Posts: 581	Re: Troubleshooting 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. Posted via Mobile Device Posted via Mobile Device Attached Images __________________ 69 C10 SWB -- Left to me by a loving father. Finishing the build we never got the chance to do together

10-06-2011, 12:33 PM	#6
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: Troubleshooting do you have cheap chrome valve covers withPVC valve installed without baffels? __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

10-06-2011, 01:28 PM	#7
ajgriffin Registered User Join Date: Feb 2008 Location: Carson, CA Posts: 581	Re: Troubleshooting 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. Posted via Mobile Device __________________ 69 C10 SWB -- Left to me by a loving father. Finishing the build we never got the chance to do together

10-06-2011, 03:17 PM	#8
MacGyver72 Registered User Join Date: Sep 2011 Location: Greencastle, IN Posts: 132	Re: Troubleshooting 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.



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