What do you think would cause.... - The 1947 - Present Chevrolet & GMC Truck Message Board Network

OldSkool71 · 10-13-2004, 10:41 PM

a popping like or back fire even though the carb? I have just replaced the carb thinking it may have been the problem but no luck. Any input would be appreciated so I can start making a list of what to go though and check.

thanks, Ron...

Longhorn Man · 10-13-2004, 10:43 PM

Timing, chipped intake valve, Timing chain jumping.

c-1072 · 10-13-2004, 10:53 PM

Put a fuel pressure guage on it make sure your getting enough fuel . Compression test would help to . Its always best when you have a drivability problem to check the main things that make you engine run . fuel and spark .

jimfulco · 10-13-2004, 10:54 PM

Fuel-fouled spark plugs will do it.

OldSkool71 · 10-13-2004, 11:23 PM

I should also mention this only happen once you press the throttle some not at an idle. It was all of a sudden one day. It was running normal like usual and then pop! And it continues to do so.

beautimus · 10-14-2004, 04:20 AM

i have seen situations where a sudden back firing problem would start,
and would be just off idle like that, (i can't explain why).
it would have an odd sound to it, kinda like hitting the carb with a wrench.
and it would turn out to be a broken rocker arm or a broken push rod.
i can't explain why, this problem doesn't make the engine backfire at idle,
but it doesn't. i don't know if thats your problem or not, but after you run into this a couple of times you can diagnose this problem from the sound the back fire makes. like i said it would sound like someone pecking on the carb with a wrench.
hope that helps you.
tony

Lippyp · 10-14-2004, 05:12 AM

I had this happen to me a bunch of times and I'm pretty sure it was just a sticking valve. I used some carb cleaner down the barrels of the carb and followed up with some fuel system cleaner in a couple of tankfulls of fuel and it stopped. The truck wasn't used all that much at the time. Gotta be worth a try

mrein3 · 10-14-2004, 07:19 AM

I have had that happen a couple of times in my truck. Every time I ended up pulling a cam out with a flat lobe. After the third time I pulled the engine.

Brainchild · 10-14-2004, 08:53 AM

Flat lobe or sticky valve or bad rocker arm/pushrod would be my guess also.At least that's where I would be looking first.Pull the valve covers,and crank it over,and watch the rocker arms to make sure they are all moving correctly.

Perchjerker · 10-14-2004, 09:30 AM

Points maybe???

OldSkool71 · 10-15-2004, 01:20 AM

I was leaning towards a valve or something myself, but im not sure. Thanks for all the input it gives me some good places to start looking.

**pjmoreland** · 04-10-2005, 01:10 PM

Did you ever get this problem fixed? I'm having a similar problem.

10-13-2004, 10:41 PM	#1
OldSkool71 C/10 CLUB MEMBER Join Date: Jul 2003 Location: Lakewood, CA Posts: 993	What do you think would cause.... a popping like or back fire even though the carb? I have just replaced the carb thinking it may have been the problem but no luck. Any input would be appreciated so I can start making a list of what to go though and check. thanks, Ron... __________________ -Ron-

10-13-2004, 11:23 PM	#5
OldSkool71 C/10 CLUB MEMBER Join Date: Jul 2003 Location: Lakewood, CA Posts: 993	I should also mention this only happen once you press the throttle some not at an idle. It was all of a sudden one day. It was running normal like usual and then pop! And it continues to do so. __________________ -Ron-

10-14-2004, 04:20 AM	#6
beautimus Registered User Join Date: Mar 2002 Location: woodstock, alabama, usa Posts: 938	i have seen situations where a sudden back firing problem would start, and would be just off idle like that, (i can't explain why). it would have an odd sound to it, kinda like hitting the carb with a wrench. and it would turn out to be a broken rocker arm or a broken push rod. i can't explain why, this problem doesn't make the engine backfire at idle, but it doesn't. i don't know if thats your problem or not, but after you run into this a couple of times you can diagnose this problem from the sound the back fire makes. like i said it would sound like someone pecking on the carb with a wrench. hope that helps you. tony __________________ i survived cancer and kidney stones, but my kids are killing me.

10-14-2004, 05:12 AM	#7
Lippyp English Chevy Owner Join Date: May 2002 Location: Shropshire, UK/ Lot, France Posts: 1,848	I had this happen to me a bunch of times and I'm pretty sure it was just a sticking valve. I used some carb cleaner down the barrels of the carb and followed up with some fuel system cleaner in a couple of tankfulls of fuel and it stopped. The truck wasn't used all that much at the time. Gotta be worth a try __________________ Phil '67 C10 long fleet. 350/TH350, 4 bbl Carter, K&N, Dual exhaust, loads of stuff coming soon 2001 S10 Blazer Daily Driver, bone stock 4 door 4x4 with manual transmission

10-14-2004, 07:19 AM	#8
mrein3 Registered User Join Date: Feb 2000 Location: Center City, MN, USA Posts: 3,254	I have had that happen a couple of times in my truck. Every time I ended up pulling a cam out with a flat lobe. After the third time I pulled the engine. __________________ '70 cab, '71 chassis, 383, TH350, NP205. '71 Malibu convertible '72 Malibu hard top Center City, MN

10-13-2004, 10:43 PM	#2
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Timing, chipped intake valve, Timing chain jumping.

10-13-2004, 10:53 PM	#3
c-1072 Registered User Join Date: Sep 2004 Location: rochester NY Posts: 777	Put a fuel pressure guage on it make sure your getting enough fuel . Compression test would help to . Its always best when you have a drivability problem to check the main things that make you engine run . fuel and spark .

10-13-2004, 10:54 PM	#4
jimfulco Registered User Join Date: May 2003 Location: Shreveport LA Posts: 3,170	Fuel-fouled spark plugs will do it.

10-14-2004, 08:53 AM	#9
Brainchild Still drivin' a Rat Rod Join Date: Sep 2004 Location: Monett Missouri Posts: 4,925	Flat lobe or sticky valve or bad rocker arm/pushrod would be my guess also.At least that's where I would be looking first.Pull the valve covers,and crank it over,and watch the rocker arms to make sure they are all moving correctly. __________________ Rusty Member #13872 Instead of saying.....you are a discomfort in the back of my front.....one should be able to say...... you are a pain in the a$# 71 GMC LWB 49 Chevy 85 Chevy G20 Check out my website

10-14-2004, 09:30 AM	#10
Perchjerker Beer Power!!!!!!!!!! Join Date: Nov 2003 Location: Nacogdoches, TX Posts: 280	Points maybe??? __________________ Rather be fishin'

10-15-2004, 01:20 AM	#11
OldSkool71 C/10 CLUB MEMBER Join Date: Jul 2003 Location: Lakewood, CA Posts: 993	I was leaning towards a valve or something myself, but im not sure. Thanks for all the input it gives me some good places to start looking. __________________ -Ron-

04-10-2005, 01:10 PM	#12
pjmoreland Senior Member Join Date: Jan 2005 Location: CA Posts: 6,011	Did you ever get this problem fixed? I'm having a similar problem.



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