motor smokes...need help

gmcguru32 · 03-12-2006, 10:19 AM

i have a 1993 gmc with a 4.3l v6 with 97,000. and it smokes at like stop lights or a long stop sign. it doesnt smoke when its cold or when im running down the road...but when i stop for anything for more than like 30 secinds it begins to smoke...ive had it checked out and some say its valve seals, some say its rings..and i was awndering if anyone else had this problem and what it was. or if anyone has and tips or ideas they would be greatly appreciated!!!thanks

mrjohnwayne · 03-12-2006, 08:53 PM

Does it smoke at startup? If so it's more likely to be valve seals. If no smoke at startup I would suggest blow-by.

chevyguy · 03-13-2006, 12:33 AM

Oh let me jump in here, if it only does it when it is warm and only at idle check the PCV valve. Very possible that it could be stuck. and that crankcase pressure has to go somewhere.

gmcguru32 · 03-13-2006, 09:00 AM

it will smoke at start-up if its warm...not when its cold...
what could i do to fix the blow by???thanks

chevyguy · 03-13-2006, 06:43 PM

If it is blow by , then rebuild, If it is a clogged PCV valve then replace it. Doesnt sound like valve seals since it doesnt do it when it is cold. Valve seals will usually cause smoke on initial start up after setting for awhile and allowing oil to seep into the cylinders. PCV valve would be the easy check. If it doesnt help then it sounds like time for forthur diagnosis that I think will lead to a rebuild.

gmcguru32 · 03-14-2006, 08:29 AM

ok well i changed my pcv valve and i checked with my fingure to make sure it had suction and it did...took it for a run and after it got warm and i would stop it would still do it...not a big deal bout the pcv valve it was only like $2...so ill probly have o rebuild huh???top end good enough???

chevyguy · 03-14-2006, 11:28 PM

No blow by is blowing past the rings. Complete rebuild.

gmcguru32 · 03-17-2006, 08:32 AM

well to tell you chevy guy...it was blow by...and it was BAD...i tore it down last night to check for blow by and my valve seals and i got the intake off for more room then i took my heads off and they didnt look bad until i put my fingers on it and i could wiggle it aroung like nothing...you could probly put a toothpick in between my cylinder wall and my piston...im not even gonna try and bore it or antything...im jst gonna give in and a go get a 350...around where i live i can buy a rebuilt 350 for the same price it would take to rebuild the pieces of mine that need done...so thanx for the tip man...that why im getting bad gas mileage also...

chevyguy · 03-18-2006, 11:14 PM

Well it aint helping if you have alot of blow by. i wish you had done a compressiion check before you tore it apart. i would be interested to know what the cylinders were reading.Putting a toothpick between the piston wall and the cylinder isnt necassarily a sign of blow by. Damaged or excessively worn rings are.

03-12-2006, 10:19 AM	#1
gmcguru32 Full Member Join Date: Mar 2006 Location: Dubois. PA Posts: 36	motor smokes...need help i have a 1993 gmc with a 4.3l v6 with 97,000. and it smokes at like stop lights or a long stop sign. it doesnt smoke when its cold or when im running down the road...but when i stop for anything for more than like 30 secinds it begins to smoke...ive had it checked out and some say its valve seals, some say its rings..and i was awndering if anyone else had this problem and what it was. or if anyone has and tips or ideas they would be greatly appreciated!!!thanks Last edited by gmcguru32; 03-12-2006 at 11:13 AM.

03-12-2006, 08:53 PM	#2
mrjohnwayne Senior Moderator Join Date: Apr 2005 Location: Texas Posts: 3,722	Does it smoke at startup? If so it's more likely to be valve seals. If no smoke at startup I would suggest blow-by. __________________ John Wayne 2000 F-350 7.3L Powerstroke 4x4

03-13-2006, 12:33 AM	#3
chevyguy Senior Member Join Date: Sep 2005 Location: ALABAMA Posts: 3,370	Oh let me jump in here, if it only does it when it is warm and only at idle check the PCV valve. Very possible that it could be stuck. and that crankcase pressure has to go somewhere. __________________ Friends dont let friends use body lifts USMC 92-96 USCG 98 to present

03-13-2006, 06:43 PM	#5
chevyguy Senior Member Join Date: Sep 2005 Location: ALABAMA Posts: 3,370	If it is blow by , then rebuild, If it is a clogged PCV valve then replace it. Doesnt sound like valve seals since it doesnt do it when it is cold. Valve seals will usually cause smoke on initial start up after setting for awhile and allowing oil to seep into the cylinders. PCV valve would be the easy check. If it doesnt help then it sounds like time for forthur diagnosis that I think will lead to a rebuild. __________________ Friends dont let friends use body lifts USMC 92-96 USCG 98 to present

03-14-2006, 11:28 PM	#7
chevyguy Senior Member Join Date: Sep 2005 Location: ALABAMA Posts: 3,370	No blow by is blowing past the rings. Complete rebuild. __________________ Friends dont let friends use body lifts USMC 92-96 USCG 98 to present

03-13-2006, 09:00 AM	#4
gmcguru32 Full Member Join Date: Mar 2006 Location: Dubois. PA Posts: 36	it will smoke at start-up if its warm...not when its cold... what could i do to fix the blow by???thanks

03-14-2006, 08:29 AM	#6
gmcguru32 Full Member Join Date: Mar 2006 Location: Dubois. PA Posts: 36	ok well i changed my pcv valve and i checked with my fingure to make sure it had suction and it did...took it for a run and after it got warm and i would stop it would still do it...not a big deal bout the pcv valve it was only like $2...so ill probly have o rebuild huh???top end good enough???

03-17-2006, 08:32 AM	#8
gmcguru32 Full Member Join Date: Mar 2006 Location: Dubois. PA Posts: 36	well to tell you chevy guy...it was blow by...and it was BAD...i tore it down last night to check for blow by and my valve seals and i got the intake off for more room then i took my heads off and they didnt look bad until i put my fingers on it and i could wiggle it aroung like nothing...you could probly put a toothpick in between my cylinder wall and my piston...im not even gonna try and bore it or antything...im jst gonna give in and a go get a 350...around where i live i can buy a rebuilt 350 for the same price it would take to rebuild the pieces of mine that need done...so thanx for the tip man...that why im getting bad gas mileage also...

03-18-2006, 11:14 PM	#9
chevyguy Senior Member Join Date: Sep 2005 Location: ALABAMA Posts: 3,370	Well it aint helping if you have alot of blow by. i wish you had done a compressiion check before you tore it apart. i would be interested to know what the cylinders were reading.Putting a toothpick between the piston wall and the cylinder isnt necassarily a sign of blow by. Damaged or excessively worn rings are. __________________ Friends dont let friends use body lifts USMC 92-96 USCG 98 to present

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