86 C10 4.3 Dead spot when accelerating - The 1947 - Present Chevrolet & GMC Truck Message Board Network

tablerock4 · 01-26-2005, 07:03 PM

When starting off, the truck will stall if I don't give if alot of gas or give it a pump as I initially accelerate. This problem is minor when the engine is cold and gets increasingly worse as the engine warms up. It's that one spot when I just start to push the accelerator pedal. It's almost like a hick-up at the very beginning of acceleration. At operating temp, I can't just lightly touch the pedal to slowly creep forward, like you would in traffic, it will stall. I have tried the following:

New Carb
New Distributer Cap & Rotor
New Ignition Wires
Advanced the timing
Increased idle speed
Checked for vacuum leaks
Cooler thermostat (helped a little)

I am really stumped. Any advice is very welcome!!

Thanks

60-66 Nut · 01-26-2005, 07:17 PM

Did you try disconnecting the EGR valve?

60-66 Nut

tablerock4 · 01-26-2005, 07:32 PM

I don't think I did. Is the EGR that saucer looking metallic thing right in front of the carb with a single vacuum line coming out of it?

C-10volvo · 01-26-2005, 07:36 PM

you got it

86-C10-V6 · 01-26-2005, 07:45 PM

Has the Carb ever been rebuilt.
If not, start there, sounds like accelerator pump is not providing enough gas.
Make sure the dual capacity pump wire on the top front of the carb is plugged in. If this is not working correctly you will get too much gas after the warmup period when the valve is supposed to be active, but what you describe sounds like a malfunctioning accelerator pump.
Hope this helps.

**smokinn** · 01-26-2005, 07:46 PM

Sounds like a carb needing adjusting.

tablerock4 · 01-26-2005, 08:54 PM

60-66 Nut...you are the Man!! Thanks to everyone for their help!

The EGR was it. I disconnected the vacuum line and it stopped stalling/sputtering immediatly. I drove around town a little and just couldn't believe it, so I hooked the vacuum line back up and sure enough the problem was there again. This is awesome! I can't thank you enough.

Should I just plug the line and valve port and call it done or should I buy a new EGR?

Thanks again

MylilBowTie · 01-26-2005, 11:58 PM

I read that backwards. It probably wouldnt hurt to get a new one and install it.

60-66 Nut · 01-27-2005, 09:56 AM

Lucky guess. Actually, my first thought was the carburator pump, like 86-C10-V6 said, but then I saw that you had already changed it. So the EGR was my next guess. Glad that worked for ya. The EGR valve itself is usually not the problem, the EGR control valve is what normaly goes bad. It won't hurt to run it with the EGR disconnected, sometimes you'll hear a little more valve clatter without it though. Also, I don't know how close they check emissions in your area. Here they don't worry so much about older vehicles.

60-66 Nut

86-C10-V6 · 01-27-2005, 03:16 PM

I completed missed the new carb at the top of your list.
If you are getting poor performance while the engine is cold, then you may have the wrong vacuum going to the EGR valve.
The EGR vacuum is normally supplied through a thermostatic switch that does not allow EGR during warm up.
There may also be a vacuum delay line but I can't remember for sure, look at your vacuum routing diagram and make sure the vacuum to the EGR is correct.
Sorry for the misleading diagnosis about the carb.
Good luck.

tablerock4 · 01-27-2005, 07:57 PM

That's quite alright, I was totally lost and thanks for the help. What you say rings true about the switch not allowing EGR when the engine is cold. It accelerated fine when cold and got increasingly worse as the engine warmed up. I'm thinking this indicates my lines are correctly hooked up and that the EGR is probably bad. But I'm not sure so I'm just gonna leave it disconnected for now. I don't want to spend the 40 or so bucks and have it not be bad.

Thanks again!!

MylilBowTie · 01-27-2005, 11:21 PM

They can be checked with a vacuum tool.

01-26-2005, 07:03 PM	#1
tablerock4 Registered User Join Date: Jan 2005 Location: Boise, ID Posts: 11	86 C10 4.3 Dead spot when accelerating When starting off, the truck will stall if I don't give if alot of gas or give it a pump as I initially accelerate. This problem is minor when the engine is cold and gets increasingly worse as the engine warms up. It's that one spot when I just start to push the accelerator pedal. It's almost like a hick-up at the very beginning of acceleration. At operating temp, I can't just lightly touch the pedal to slowly creep forward, like you would in traffic, it will stall. I have tried the following: New Carb New Distributer Cap & Rotor New Ignition Wires Advanced the timing Increased idle speed Checked for vacuum leaks Cooler thermostat (helped a little) I am really stumped. Any advice is very welcome!! Thanks

01-26-2005, 07:17 PM	#2
60-66 Nut Professional Beer Tester Join Date: Aug 2004 Location: Louisiana Posts: 453	Did you try disconnecting the EGR valve? 60-66 Nut __________________ 60 Ford F100 Custom Cab 61 Apache Short Fleetside 64 C10 Short Stepside 65 C80 409 V8 5spd(X-Firetruck) 83 GMC 350 Olds Diesel 85 GMC Short Bed 86 GMC Short Bed 90 GMC R3500 Crew Cab 92 GMC 1500

01-26-2005, 07:36 PM	#4
C-10volvo Registered User Join Date: May 2003 Location: Lake Oswego, Oregon Posts: 1,028	you got it __________________ Ken Morgan For fun: 1964 Volvo 122 For slow: 1984 Chevrolet C-10 For everything else: 1997 BMW M3

01-26-2005, 07:45 PM	#5
86-C10-V6 Shadetree Mechanic Join Date: Oct 2002 Location: Youngsville, NC Posts: 100	Sounds like Carburetor, not ignition. Has the Carb ever been rebuilt. If not, start there, sounds like accelerator pump is not providing enough gas. Make sure the dual capacity pump wire on the top front of the carb is plugged in. If this is not working correctly you will get too much gas after the warmup period when the valve is supposed to be active, but what you describe sounds like a malfunctioning accelerator pump. Hope this helps. __________________ Dave M. (Hacksaw) 86 C10 Scottsdale LWB, 4.3L, Edelbrock 1904, K&N, 700R4, 3.08 Auburn Performance 89 GMC S-15 Extended Cab 4x4, 4.3L, FI 98 K1500 Xcab, 5.7L, 3.43 Gov-Lok

01-26-2005, 11:58 PM	#8
MylilBowTie Right turn Clyde Join Date: Nov 2002 Location: Cincinnati, Ohio Posts: 2,911	I read that backwards. It probably wouldnt hurt to get a new one and install it. __________________ 1974 C25 LWB: 454 4bbl Carb / TH400 / 3.73 1992 Camaro RS 305 TBI Last edited by MylilBowTie; 01-27-2005 at 12:00 AM.

01-26-2005, 07:32 PM	#3
tablerock4 Registered User Join Date: Jan 2005 Location: Boise, ID Posts: 11	I don't think I did. Is the EGR that saucer looking metallic thing right in front of the carb with a single vacuum line coming out of it?

01-26-2005, 07:46 PM	#6
smokinn Senior Member Join Date: Aug 2002 Location: omaha,Ne Posts: 617	Sounds like a carb needing adjusting.

01-26-2005, 08:54 PM	#7
tablerock4 Registered User Join Date: Jan 2005 Location: Boise, ID Posts: 11	60-66 Nut...you are the Man!! Thanks to everyone for their help! The EGR was it. I disconnected the vacuum line and it stopped stalling/sputtering immediatly. I drove around town a little and just couldn't believe it, so I hooked the vacuum line back up and sure enough the problem was there again. This is awesome! I can't thank you enough. Should I just plug the line and valve port and call it done or should I buy a new EGR? Thanks again

01-27-2005, 09:56 AM	#9
60-66 Nut Professional Beer Tester Join Date: Aug 2004 Location: Louisiana Posts: 453	Lucky guess. Actually, my first thought was the carburator pump, like 86-C10-V6 said, but then I saw that you had already changed it. So the EGR was my next guess. Glad that worked for ya. The EGR valve itself is usually not the problem, the EGR control valve is what normaly goes bad. It won't hurt to run it with the EGR disconnected, sometimes you'll hear a little more valve clatter without it though. Also, I don't know how close they check emissions in your area. Here they don't worry so much about older vehicles. 60-66 Nut __________________ 60 Ford F100 Custom Cab 61 Apache Short Fleetside 64 C10 Short Stepside 65 C80 409 V8 5spd(X-Firetruck) 83 GMC 350 Olds Diesel 85 GMC Short Bed 86 GMC Short Bed 90 GMC R3500 Crew Cab 92 GMC 1500

01-27-2005, 03:16 PM	#10
86-C10-V6 Shadetree Mechanic Join Date: Oct 2002 Location: Youngsville, NC Posts: 100	Missed the new carb I completed missed the new carb at the top of your list. If you are getting poor performance while the engine is cold, then you may have the wrong vacuum going to the EGR valve. The EGR vacuum is normally supplied through a thermostatic switch that does not allow EGR during warm up. There may also be a vacuum delay line but I can't remember for sure, look at your vacuum routing diagram and make sure the vacuum to the EGR is correct. Sorry for the misleading diagnosis about the carb. Good luck. __________________ Dave M. (Hacksaw) 86 C10 Scottsdale LWB, 4.3L, Edelbrock 1904, K&N, 700R4, 3.08 Auburn Performance 89 GMC S-15 Extended Cab 4x4, 4.3L, FI 98 K1500 Xcab, 5.7L, 3.43 Gov-Lok

01-27-2005, 07:57 PM	#11
tablerock4 Registered User Join Date: Jan 2005 Location: Boise, ID Posts: 11	That's quite alright, I was totally lost and thanks for the help. What you say rings true about the switch not allowing EGR when the engine is cold. It accelerated fine when cold and got increasingly worse as the engine warmed up. I'm thinking this indicates my lines are correctly hooked up and that the EGR is probably bad. But I'm not sure so I'm just gonna leave it disconnected for now. I don't want to spend the 40 or so bucks and have it not be bad. Thanks again!!

01-27-2005, 11:21 PM	#12
MylilBowTie Right turn Clyde Join Date: Nov 2002 Location: Cincinnati, Ohio Posts: 2,911	They can be checked with a vacuum tool. __________________ 1974 C25 LWB: 454 4bbl Carb / TH400 / 3.73 1992 Camaro RS 305 TBI



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