Truck won't idle below 1000 RPM all of a sudden - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Black70c10 · 02-16-2014, 03:02 PM

Hey guys, I'm having a lot of trouble all of a sudden with my trucks idle. It used to idle just fine all day at 500 rpm with timing 18 before TDC. Had he timing a little closer to tdc but it would bog down under WOT so i found that this timing worked the best. Out of no where after changing the oil yesterday, the thing will not idle below 1000 rpm, it will sputter and die. I cannot seem to locate the issue. I have not made any adjustments to the timing and or idle mixture screws.

t's a small block with an edelbrock 600. Anyone have any insight into this issue?

72_swb · 02-16-2014, 03:06 PM

Did you knock off a vacumn line maybe. just a thought

Black70c10 · 02-16-2014, 04:26 PM

Yeah I thought about a vacuum leak but I don't see anything that was disconnected.. Very bizarre what's happening.. I played with the idle mixture just a little bit and it will now idle around where it used to (500-600) but it's definitely not right, it's acting a little erratic. When you bump the throttle it won't come down quickly in RPM like it used to, it will go up in speed and then hesitate and slowly come down in speed. I took it for a spin around the block and when you ease into the throttle it hesitates for a fraction of a second before a slight jolt forward in speed... It's fine under WOT but off the line it will hesitate and the idle just seems rough. Up and down maybe 50-100 RPM randomly... Sounds like a vacuum leak but I don't know! Thoughts?

Sillyoldman · 02-16-2014, 04:56 PM

Vacuum leak comes to mind first.

boynton · 02-16-2014, 05:01 PM

I would agree. You can take your air cleaner off start it up and cover the top of the carb with your hands if it starts to idle correctly then you have a vacuum leak. My carb had a leak inside and I couldn't figure it out put a spare carb on and it ran like a champ.

1972RedNeck · 02-16-2014, 05:01 PM

Get some WD-40 and spray around the carb. If you're bored, use ether.

Black70c10 · 02-16-2014, 06:40 PM

Thanks for the help guys, I'll try that. I'll check all around, hoses to and from valve covers, brake booster, carb, etc.. Let you know what I find.

02-16-2014, 03:02 PM	#1
Black70c10 Registered User Join Date: Sep 2013 Location: Houston, TX Posts: 44	Truck won't idle below 1000 RPM all of a sudden Hey guys, I'm having a lot of trouble all of a sudden with my trucks idle. It used to idle just fine all day at 500 rpm with timing 18 before TDC. Had he timing a little closer to tdc but it would bog down under WOT so i found that this timing worked the best. Out of no where after changing the oil yesterday, the thing will not idle below 1000 rpm, it will sputter and die. I cannot seem to locate the issue. I have not made any adjustments to the timing and or idle mixture screws. t's a small block with an edelbrock 600. Anyone have any insight into this issue?

02-16-2014, 03:06 PM	#2
72_swb Registered User Join Date: Feb 2014 Location: dallas area Posts: 221	Re: Truck won't idle below 1000 RPM all of a sudden Did you knock off a vacumn line maybe. just a thought

02-16-2014, 04:26 PM	#3
Black70c10 Registered User Join Date: Sep 2013 Location: Houston, TX Posts: 44	Re: Truck won't idle below 1000 RPM all of a sudden Yeah I thought about a vacuum leak but I don't see anything that was disconnected.. Very bizarre what's happening.. I played with the idle mixture just a little bit and it will now idle around where it used to (500-600) but it's definitely not right, it's acting a little erratic. When you bump the throttle it won't come down quickly in RPM like it used to, it will go up in speed and then hesitate and slowly come down in speed. I took it for a spin around the block and when you ease into the throttle it hesitates for a fraction of a second before a slight jolt forward in speed... It's fine under WOT but off the line it will hesitate and the idle just seems rough. Up and down maybe 50-100 RPM randomly... Sounds like a vacuum leak but I don't know! Thoughts?

02-16-2014, 04:56 PM	#4
Sillyoldman #16876 Join Date: Apr 2005 Location: Auburn WA Posts: 12,266	Re: Truck won't idle below 1000 RPM all of a sudden Vacuum leak comes to mind first. __________________ Posted via Stationary Device '71 Custom Deluxe C-20 402. '67 Buick Special 455. '49 Plymouth Special Deluxe. *"I love that old car smell"* *Some people are like Slinkies... not really good for anything, but they still bring a smile to your face when you push them down a flight of stairs.*

02-16-2014, 05:01 PM	#5
boynton Registered User Join Date: Feb 2012 Location: Salado, Texas Posts: 1,418	Re: Truck won't idle below 1000 RPM all of a sudden I would agree. You can take your air cleaner off start it up and cover the top of the carb with your hands if it starts to idle correctly then you have a vacuum leak. My carb had a leak inside and I couldn't figure it out put a spare carb on and it ran like a champ. __________________ Just trying to figure this out... 1970 SWB Step-Side http://67-72chevytrucks.com/vboard/s...d.php?t=552980 1970 LWB http://67-72chevytrucks.com/vboard/s...d.php?t=584499 1970 SWB One Owner Step Side 6.0 LY6/6L90 http://67-72chevytrucks.com/vboard/s...d.php?t=617630 Junkyard's 1971 short wide http://67-72chevytrucks.com/vboard/s...86#post7531186

02-16-2014, 06:40 PM	#7
Black70c10 Registered User Join Date: Sep 2013 Location: Houston, TX Posts: 44	Re: Truck won't idle below 1000 RPM all of a sudden Thanks for the help guys, I'll try that. I'll check all around, hoses to and from valve covers, brake booster, carb, etc.. Let you know what I find.



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.