Bad gas or jumped timing?....take a guess - The 1947 - Present Chevrolet & GMC Truck Message Board Network

swb85 · 05-15-2006, 02:47 PM

Alright everyone, put in your vote. I'm arguing w/myself as I post this, so bear with me.

Yesterday I found a quick shop selling gas 15 cents cheaper than everyone else in town and I was empty so I filled up and drove home. Now today the truck is pinging like crazy under any kind of load. Bad gas right??....Well it's suddenly bucking quite a bit under light throttle at lower rpm in every gear (4 spd). Under normal crusing on the highway it runs normal and I can give ~1/2 throttle without it pinging, but any more and it pings bad. So when I got home for lunch today I shut it off and tried to start it right back up. It didn't turn over smoothly, jumped around a bit but eventually started....made me think waaaaay too much timing....bad gas wouldn't do that. Checked the dizzy and it hasn't jumped, hold down is still secure. Didn't have time to pull the cap. After lunch it started right up smoothly, but idle was jumping around quite a bit. Same symptoms on the way back to work.

The motor is rebuilt 350 (PO did it) and only has 12k miles on it. After hearing the pinging, I was REALLY hoping it was just bad gas....but now I have a sinking feeling the timing jumped internally with the rough turning over when hot and the bucking. The PO was good about replacing everything on the rebuild, so I'd have a hard time believing he didn't replace the timing set (I've never pulled the cover, never had to set the timing). The thing ran flawlessly yesterday....

Thoughts?...Opinions?....Ideas?.....Suggestions?

Thanks guys.

Oldtruckfanatic · 05-15-2006, 02:58 PM

Sounds like water in the gas. It's almost too much of a coincidence to have it start acting funny right after a fill up. If you pump some from your fuel line into a clear glass you can see the water in it. I have had it happen before.

rockman20 · 05-15-2006, 03:21 PM

Quote:

Originally Posted by Oldtruckfanatic

Sounds like water in the gas. It's almost too much of a coincidence to have it start acting funny right after a fill up. If you pump some from your fuel line into a clear glass you can see the water in it. I have had it happen before.

This, I would say, sounds a lot more reasonable. There was a station in the area here that you couldn't even get gas out of the pump this past winter. They had to dump HEAT in the hose just to unthaw the pump handle!

swb85 · 05-15-2006, 03:42 PM

Good thoughts.....I actually just changed my fuel filter a few mins ago and poured the gas into a lil paper cup--didn't see any water but it was only a couple tablespoons. I'll dump some HEET in the tank after work and see if that helps. I thought water in the gas would just make it spit/sputter, not ping like I put 87 octane in a 14:1 motor.

Oldtruckfanatic · 05-15-2006, 03:46 PM

Bad gas or gas that has water in it will cause pinging and spark knock fairly efficiently. Also water doesn't compress like gas does so if there is enough in the system it can make the engine turn over irregularly. The water isn't always easy to see in anything other than glass because it's just a layer of fuel thats kinda cloudy and pale looking.

swb85 · 05-15-2006, 05:53 PM

Alright, stuck some heet in the tank for the ride home....we'll see what happens!

Oldtruckfanatic · 05-15-2006, 05:57 PM

Hope it works out for ya.

rockman20 · 05-17-2006, 10:47 AM

Let us know. I am curious to see what happens with the HEET and then when you get some fresh gas in it.

86 GMG · 05-17-2006, 11:28 AM

it seem to be unanimous (sp?) bad \ water fuel heet is a good idea but ithink an bottle of octane boost would help as well atleast for detination purposes. best of luck to you andkeep us informed of the situation

79BIG10 · 05-17-2006, 12:46 PM

Could it have been the new ethanol gas they came out with? I don't know if the same would happen with our engine systems but I'm thinking it could be that causing the lower octane and casuing the pinging.

swb85 · 05-17-2006, 03:59 PM

Update: I'm almost done with this tank of gas, gonna fill up tonight with 91 octane and put another bottle of heet in the tank in case there's any moisture left. It's running a little better....not bucking or hunting for idle, but it's still pinging really bad if you get into the throttle under any kind of load. Keep your foot out of it and it runs great.

79Big10: The station I bought the crappy gas from doesn't have ethanol in it's fuels...yet. I am curious about the effects ethanol will have on our vehicles though.

05-15-2006, 02:47 PM	#1
swb85 On a budget like Fred Sanford Join Date: Oct 2005 Location: Topeka, KS Posts: 2,031	Bad gas or jumped timing?....take a guess Alright everyone, put in your vote. I'm arguing w/myself as I post this, so bear with me. Yesterday I found a quick shop selling gas 15 cents cheaper than everyone else in town and I was empty so I filled up and drove home. Now today the truck is pinging like crazy under any kind of load. Bad gas right??....Well it's suddenly bucking quite a bit under light throttle at lower rpm in every gear (4 spd). Under normal crusing on the highway it runs normal and I can give ~1/2 throttle without it pinging, but any more and it pings bad. So when I got home for lunch today I shut it off and tried to start it right back up. It didn't turn over smoothly, jumped around a bit but eventually started....made me think waaaaay too much timing....bad gas wouldn't do that. Checked the dizzy and it hasn't jumped, hold down is still secure. Didn't have time to pull the cap. After lunch it started right up smoothly, but idle was jumping around quite a bit. Same symptoms on the way back to work. The motor is rebuilt 350 (PO did it) and only has 12k miles on it. After hearing the pinging, I was REALLY hoping it was just bad gas....but now I have a sinking feeling the timing jumped internally with the rough turning over when hot and the bucking. The PO was good about replacing everything on the rebuild, so I'd have a hard time believing he didn't replace the timing set (I've never pulled the cover, never had to set the timing). The thing ran flawlessly yesterday.... Thoughts?...Opinions?....Ideas?.....Suggestions? Thanks guys. __________________ '85 Silverado swb: 383 stroker, 10.5:1, vortec heads, 232/238 roller cam, RPM air gap, performer 750 carb, stainless longtubes, 3" duals/super 44's, T56/4.11 383ci build / exterior refresh thread '98 Camaro z28: 370ci twin turbo 370ci build '01 Tahoe LT 4x4: 5.3, longtubes/ory, magnaflow duals, custom tune....wife's DD Last edited by swb85; 05-15-2006 at 02:48 PM.

05-15-2006, 02:58 PM	#2
Oldtruckfanatic Truck junkie Join Date: May 2006 Location: Reno NV Posts: 697	Re: Bad gas or jumped timing?....take a guess Sounds like water in the gas. It's almost too much of a coincidence to have it start acting funny right after a fill up. If you pump some from your fuel line into a clear glass you can see the water in it. I have had it happen before.

05-15-2006, 03:42 PM	#4
swb85 On a budget like Fred Sanford Join Date: Oct 2005 Location: Topeka, KS Posts: 2,031	Re: Bad gas or jumped timing?....take a guess Good thoughts.....I actually just changed my fuel filter a few mins ago and poured the gas into a lil paper cup--didn't see any water but it was only a couple tablespoons. I'll dump some HEET in the tank after work and see if that helps. I thought water in the gas would just make it spit/sputter, not ping like I put 87 octane in a 14:1 motor. __________________ '85 Silverado swb: 383 stroker, 10.5:1, vortec heads, 232/238 roller cam, RPM air gap, performer 750 carb, stainless longtubes, 3" duals/super 44's, T56/4.11 383ci build / exterior refresh thread '98 Camaro z28: 370ci twin turbo 370ci build '01 Tahoe LT 4x4: 5.3, longtubes/ory, magnaflow duals, custom tune....wife's DD

05-15-2006, 03:46 PM	#5
Oldtruckfanatic Truck junkie Join Date: May 2006 Location: Reno NV Posts: 697	Re: Bad gas or jumped timing?....take a guess Bad gas or gas that has water in it will cause pinging and spark knock fairly efficiently. Also water doesn't compress like gas does so if there is enough in the system it can make the engine turn over irregularly. The water isn't always easy to see in anything other than glass because it's just a layer of fuel thats kinda cloudy and pale looking. Last edited by Oldtruckfanatic; 05-15-2006 at 03:47 PM.

05-15-2006, 05:53 PM	#6
swb85 On a budget like Fred Sanford Join Date: Oct 2005 Location: Topeka, KS Posts: 2,031	Re: Bad gas or jumped timing?....take a guess Alright, stuck some heet in the tank for the ride home....we'll see what happens! __________________ '85 Silverado swb: 383 stroker, 10.5:1, vortec heads, 232/238 roller cam, RPM air gap, performer 750 carb, stainless longtubes, 3" duals/super 44's, T56/4.11 383ci build / exterior refresh thread '98 Camaro z28: 370ci twin turbo 370ci build '01 Tahoe LT 4x4: 5.3, longtubes/ory, magnaflow duals, custom tune....wife's DD

05-15-2006, 05:57 PM	#7
Oldtruckfanatic Truck junkie Join Date: May 2006 Location: Reno NV Posts: 697	Re: Bad gas or jumped timing?....take a guess Hope it works out for ya.

05-17-2006, 10:47 AM	#8
rockman20 "The dude abides" Join Date: Apr 2003 Location: North Dakota Posts: 472	Re: Bad gas or jumped timing?....take a guess Let us know. I am curious to see what happens with the HEET and then when you get some fresh gas in it. __________________ RockMan 1993 Chevy Silverado C3500 1 ton dually 1994 Honda Civic 1969 Oldsmobile Cutlass S 1953 IH Farmall Super M New to the fleet: 1992 Subaru Loyal

05-17-2006, 11:28 AM	#9
86 GMG Registered User Join Date: Apr 2005 Location: Tulsa Oklahoma Posts: 943	Re: Bad gas or jumped timing?....take a guess it seem to be unanimous (sp?) bad \ water fuel heet is a good idea but ithink an bottle of octane boost would help as well atleast for detination purposes. best of luck to you andkeep us informed of the situation __________________ square body trucks an addiction or an investment either way they consume all my extra time and money

05-17-2006, 12:46 PM	#10
79BIG10 I'm back with 2nd truck! Join Date: Feb 2002 Location: Texas Posts: 3,775	Re: Bad gas or jumped timing?....take a guess Could it have been the new ethanol gas they came out with? I don't know if the same would happen with our engine systems but I'm thinking it could be that causing the lower octane and casuing the pinging. __________________ 1979 Chevrolet Bonanza Big10 "Tootsie Roll" 1985 Chevrolet Silverado (wife's) Member of the Southern Bowties Club "Don't underestimate how sexy a fat man who drinks to excess can be." Homer Simpson

05-17-2006, 03:59 PM	#11
swb85 On a budget like Fred Sanford Join Date: Oct 2005 Location: Topeka, KS Posts: 2,031	Re: Bad gas or jumped timing?....take a guess Update: I'm almost done with this tank of gas, gonna fill up tonight with 91 octane and put another bottle of heet in the tank in case there's any moisture left. It's running a little better....not bucking or hunting for idle, but it's still pinging really bad if you get into the throttle under any kind of load. Keep your foot out of it and it runs great. 79Big10: The station I bought the crappy gas from doesn't have ethanol in it's fuels...yet. I am curious about the effects ethanol will have on our vehicles though. __________________ '85 Silverado swb: 383 stroker, 10.5:1, vortec heads, 232/238 roller cam, RPM air gap, performer 750 carb, stainless longtubes, 3" duals/super 44's, T56/4.11 383ci build / exterior refresh thread '98 Camaro z28: 370ci twin turbo 370ci build '01 Tahoe LT 4x4: 5.3, longtubes/ory, magnaflow duals, custom tune....wife's DD



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