Sputtering @ highway speeds.... - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**JIMs70GMC** · 03-26-2002, 08:53 PM

What could it be? Engine idle has also crept up from about 800 RPM to 1000 RPM unable to adjust down, vacuum leak? I sprayed starter fluid around carb could not get change in RPM. At 55-60 (turning 2700 RPM) truck starts to jerk and back fire lift foot off gas and slow down runs fine(I was on the shoulder of the road). Put her in 3rd and run up to 3000 RPM doing 35 MPH no problems. Shift into 4th get up to speed and truck starts sputtering again after about 5 minutes. Have not tried going 55 again, got off interstate had no problem around town did get up to 50 though for about 2 miles no problems. Never shut the truck off. Could it be plug wires? The ones I have I installed 2 years and 31,000 miles ago. I have replaced the rotor and dizzy cap since then and also installed a pertronix unit, I figured it would not care about the speed, who knows. My carb does have 3 vacuum ports blocked off and all 3 seem intact. Power brake hose, PCV hose and vacuum advance hose seem ok also. Could it be bad gas or fuel filter? My tank is fairly low now, but was over half full on the interstate. I did replace the fuel filter a year ago, about 16,000 miles. One other thing I had been on the interstate for about 20 miles before this started today. Also, the idle was fine this morning before I left on my 42 mile trip to work.

Any ideas? Thanks,

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1970 GMC K25 Custom
Chesapeake, VA
My 70 GMCor Webshots http://community.webshots.com/user/70gmc

[This message has been edited by JIMs70GMC (edited March 26, 2002).]

Bill72BB · 03-26-2002, 09:02 PM

Jim, I just fixed a similar problem by replacing the fuel filter ,it had less than 16,000 on it .
Bill

------------------
72 3/4ton Custom Camper BB,400 air,ps,pb,leafsprings
tilt,3.54 . 82 chevy silverado sb ,ps,pb pw,pd,air 350/350 Flowmaster 40.
Torrance Calif.

" If I knew I was going to live this long I would have taken better care of myself "

**JIMs70GMC** · 03-26-2002, 09:26 PM

That's what I was thinking and going to try first, luckily when I replaced it last year I bought a pack of 10 nylon washers for the carb inlet, all I'll need is the filter. Thanks,

busterwivell · 03-26-2002, 09:31 PM

Filter is my best guess. That's where I'd start.

*Fast68Chevy* · 03-26-2002, 09:34 PM

i have had the problem of bent over fuel hose at the fuel pump before and it caused engine to cut out and lose power at higher rpm cruising, also if the timing is not advancing, IE vac advance hose not connected to ported location on carb or advance weights frozen, or timing too retared or advanced.

------------------
-71/C-10(thx teeitup and crews!)350 4+4/CH465(thx 71Chev, GMCPaul, and CPNE)longfleet bed(thnx meathead95)!still building it-
-'84 Z28(Z28) 1G1AP87GXEL100000 with H.O. 305/4bbl/190net/hp(L69) 3.73 rear(GT4/YC4) 700R4(MD8-MXO) & other goodies

-79 G20 pass van, 350/th350/10bolt,
paint is overrated
Randy- Lincoln, IL

r68c30@hotmail.com
© RSS Enterprises 2000

lukecp · 03-26-2002, 11:18 PM

I agree with these guys, start with the filter. A clogged one will allow the engine to idle and run fine, but cough and die at higher speeds. If you are still using the filter that goes in the carb where the line comes in, i would suggest that you ditch it and get a inline filter. A Fram G3 is what i have, simply take out the stock filter, put the line back in, then cut the fuel line between the pump and carb, and install the inline filter. It will last longer and not clog up as easy. I would reccomend using carb cleaner instead of starting fluid checking for vaccum leaks, it works as good but is alot safer. Did you check with the starting fluid at the ends of all the vaccum lines, and where they all connect together and go into the intake manifold? Good luck!

------------------
Lucas

drop_shift@hotmail.com

My Daily-Driver: '72 Chevy LWB Custom/10. Rebuilt 350, 300 HP thanks to a few go-fast goodies. Ochre with a white top. Future plans include a frame off restoration, and maybe a blown 383.

704x4 · 03-26-2002, 11:36 PM

most of the time when an engine idle goes up it means your distributor slipped advancing your timing too high.

does it ping under a heavy load?

even if it doesn't i would check it anyway.

**JIMs70GMC** · 03-27-2002, 09:17 PM

I'm going to install an inline filter as suggested and I'll check the timing. I have some carb cleaner, I'll try it. Thanks,

------------------
1970 GMC K25 Custom
Chesapeake, VA
My 70 GMCor Webshots http://community.webshots.com/user/70gmc

70-K10-292 · 03-27-2002, 11:06 PM

Dumb Question is your TCS Transmission Controlled Spark still hooked up or is it disconnected?

------------------
1970 K-10 292 Longbed stepside powersteering but manual brakes!Factory step bumper,Deluxe gauges no Tach 4 speed manual 1 out of 464 made with protectoplate intact.Its basic for a farm truck

**JIMs70GMC** · 03-28-2002, 09:30 PM

70-K10-292, do not have TCS, that's on auto tranny's only, right?

704X4, checked timing today and your right was 4 degrees further advanced. Retarded it and idle is back at 800(approx).

Have not replaced the fuel filter will do that after I replace the front shoes(failed state inspection). Is 32,000 miles on the front shoes good wear? Previous owner replaced them just before I bought the truck.

Update: replaced fuel filter, that was the problem.

Thanks,

------------------
1970 GMC K25 Custom
Chesapeake, VA
My 70 GMC or Webshots My 70 GMC on webshots

[This message has been edited by JIMs70GMC (edited March 29, 2002).]

03-26-2002, 08:53 PM	#1
JIMs70GMC user # 2756 Join Date: Jun 2001 Location: Chesapeake, Virginia Posts: 4,612	Sputtering @ highway speeds.... What could it be? Engine idle has also crept up from about 800 RPM to 1000 RPM unable to adjust down, vacuum leak? I sprayed starter fluid around carb could not get change in RPM. At 55-60 (turning 2700 RPM) truck starts to jerk and back fire lift foot off gas and slow down runs fine(I was on the shoulder of the road). Put her in 3rd and run up to 3000 RPM doing 35 MPH no problems. Shift into 4th get up to speed and truck starts sputtering again after about 5 minutes. Have not tried going 55 again, got off interstate had no problem around town did get up to 50 though for about 2 miles no problems. Never shut the truck off. Could it be plug wires? The ones I have I installed 2 years and 31,000 miles ago. I have replaced the rotor and dizzy cap since then and also installed a pertronix unit, I figured it would not care about the speed, who knows. My carb does have 3 vacuum ports blocked off and all 3 seem intact. Power brake hose, PCV hose and vacuum advance hose seem ok also. Could it be bad gas or fuel filter? My tank is fairly low now, but was over half full on the interstate. I did replace the fuel filter a year ago, about 16,000 miles. One other thing I had been on the interstate for about 20 miles before this started today. Also, the idle was fine this morning before I left on my 42 mile trip to work. Any ideas? Thanks, ------------------ 1970 GMC K25 Custom Chesapeake, VA My 70 GMCor Webshots http://community.webshots.com/user/70gmc [This message has been edited by JIMs70GMC (edited March 26, 2002).] __________________ 1970 K25, 8' stepside bed 350/465/205 44 up front, 60 in the rear 4.10s rolling on 33" Dunlop MTs 1986 K5, 350/465/208 Dana 60/14 bolt from a cucv 36" Super Swampers TSL/SX 1983 K20 w/ CUCV axles, 350/700R4/208 sitting on 37" Goodyears 1986 M1031 6.2 diesel, TH400/NP205 locker in the rear and a LS in the front, all stock for now..... 1986 K30, 350/400/205 dana 60 and 14 bolt. I kept the drivetrain. Body/bad and chassis are gone. 1981 K30, 350/465/205 dana 60 and dually 14 bolt. Has a G80, and a flat bed. Going to replace the flat bed. 1985 K20, 350/400/208 10 bolt and SF 14 bolt. I wonder where I can find some 1 tons. Hmmmmm

03-26-2002, 09:02 PM	#2
Bill72BB Thats the Hillbilly way Join Date: Jul 2001 Location: Torrance,Ca Posts: 5,980	Jim, I just fixed a similar problem by replacing the fuel filter ,it had less than 16,000 on it . Bill ------------------ 72 3/4ton Custom Camper BB,400 air,ps,pb,leafsprings tilt,3.54 . 82 chevy silverado sb ,ps,pb pw,pd,air 350/350 Flowmaster 40. Torrance Calif. " If I knew I was going to live this long I would have taken better care of myself " __________________ BILL Torrance Calif 90504 Member DUF Club Member Old Farts Club 72 3/4ton Custom Camper BB402/400 trans Dynomax Cerama-coat headers , Hei distributor ,Edelbrock 1411 air,ps,pb,leafsprings ,98 chevy 60/40 seat,S10 shoulder belts tilt,3.54 Dana 60 rear. 16" Eagle wheels with LT265/75 16 tires,Gaylord Lid,H4 headlights with 100W relay conversion. " If I knew I was going to live this long I would have taken better care of myself " Marriage changes passion...suddenly you're in bed with a relative. A GUY'S PRAYER.... Lord, I pray for a nympho with huge boobs who owns a liquor store and likes to fish and hunt and has a Harley .Amen ,

03-26-2002, 09:26 PM	#3
JIMs70GMC user # 2756 Join Date: Jun 2001 Location: Chesapeake, Virginia Posts: 4,612	That's what I was thinking and going to try first, luckily when I replaced it last year I bought a pack of 10 nylon washers for the carb inlet, all I'll need is the filter. Thanks, __________________ 1970 K25, 8' stepside bed 350/465/205 44 up front, 60 in the rear 4.10s rolling on 33" Dunlop MTs 1986 K5, 350/465/208 Dana 60/14 bolt from a cucv 36" Super Swampers TSL/SX 1983 K20 w/ CUCV axles, 350/700R4/208 sitting on 37" Goodyears 1986 M1031 6.2 diesel, TH400/NP205 locker in the rear and a LS in the front, all stock for now..... 1986 K30, 350/400/205 dana 60 and 14 bolt. I kept the drivetrain. Body/bad and chassis are gone. 1981 K30, 350/465/205 dana 60 and dually 14 bolt. Has a G80, and a flat bed. Going to replace the flat bed. 1985 K20, 350/400/208 10 bolt and SF 14 bolt. I wonder where I can find some 1 tons. Hmmmmm

03-26-2002, 09:31 PM	#4
busterwivell Registered User Join Date: Jan 2002 Location: Sahuarita, AZ USA Posts: 2,033	Filter is my best guess. That's where I'd start. __________________ Bill - Tucson, AZ 47 Chevrolet 2 dr sedan 56 Chevrolet 210 2 dr sedan 66 Chevrolet Malibu 2 dr 4 speed 71 Chevrolet C30 Longhorn 86 Chevrolet Monte Carlo SS (Sold) 01 Chevrolet Tahoe IM - BUSTERWIVE@aol.com

03-26-2002, 11:18 PM	#6
lukecp Formerly yellow72custom Join Date: May 2001 Location: Austin, TX Posts: 7,531	I agree with these guys, start with the filter. A clogged one will allow the engine to idle and run fine, but cough and die at higher speeds. If you are still using the filter that goes in the carb where the line comes in, i would suggest that you ditch it and get a inline filter. A Fram G3 is what i have, simply take out the stock filter, put the line back in, then cut the fuel line between the pump and carb, and install the inline filter. It will last longer and not clog up as easy. I would reccomend using carb cleaner instead of starting fluid checking for vaccum leaks, it works as good but is alot safer. Did you check with the starting fluid at the ends of all the vaccum lines, and where they all connect together and go into the intake manifold? Good luck! ------------------ Lucas drop_shift@hotmail.com My Daily-Driver: '72 Chevy LWB Custom/10. Rebuilt 350, 300 HP thanks to a few go-fast goodies. Ochre with a white top. Future plans include a frame off restoration, and maybe a blown 383. __________________ '72 Chevy C10 Mild 350/TH350/3.07. Ochre/White. Old high school ride. '70 GMC C2500 '62 327 4bbl/SM465/4.56-geared Dana 60. White/White. Project or parts truck. '97 Saturn SL DD. 1.9/5-speed. 40+ highway mpg

03-26-2002, 09:34 PM	#5
Fast68Chevy Account Suspended Join Date: May 2000 Location: IL Posts: 0	i have had the problem of bent over fuel hose at the fuel pump before and it caused engine to cut out and lose power at higher rpm cruising, also if the timing is not advancing, IE vac advance hose not connected to ported location on carb or advance weights frozen, or timing too retared or advanced. ------------------ -71/C-10(thx teeitup and crews!)350 4+4/CH465(thx 71Chev, GMCPaul, and CPNE)longfleet bed(thnx meathead95)!still building it- -'84 Z28(Z28) 1G1AP87GXEL100000 with H.O. 305/4bbl/190net/hp(L69) 3.73 rear(GT4/YC4) 700R4(MD8-MXO) & other goodies -79 G20 pass van, 350/th350/10bolt, paint is overrated Randy- Lincoln, IL r68c30@hotmail.com © RSS Enterprises 2000

03-26-2002, 11:36 PM	#7
704x4 Registered User Join Date: Feb 2002 Location: Greene, Iowa Posts: 150	most of the time when an engine idle goes up it means your distributor slipped advancing your timing too high. does it ping under a heavy load? even if it doesn't i would check it anyway. __________________ 70 3/4 ton 4x4 FOR SALE Greene, IA

03-27-2002, 09:17 PM	#8
JIMs70GMC user # 2756 Join Date: Jun 2001 Location: Chesapeake, Virginia Posts: 4,612	I'm going to install an inline filter as suggested and I'll check the timing. I have some carb cleaner, I'll try it. Thanks, ------------------ 1970 GMC K25 Custom Chesapeake, VA My 70 GMCor Webshots http://community.webshots.com/user/70gmc __________________ 1970 K25, 8' stepside bed 350/465/205 44 up front, 60 in the rear 4.10s rolling on 33" Dunlop MTs 1986 K5, 350/465/208 Dana 60/14 bolt from a cucv 36" Super Swampers TSL/SX 1983 K20 w/ CUCV axles, 350/700R4/208 sitting on 37" Goodyears 1986 M1031 6.2 diesel, TH400/NP205 locker in the rear and a LS in the front, all stock for now..... 1986 K30, 350/400/205 dana 60 and 14 bolt. I kept the drivetrain. Body/bad and chassis are gone. 1981 K30, 350/465/205 dana 60 and dually 14 bolt. Has a G80, and a flat bed. Going to replace the flat bed. 1985 K20, 350/400/208 10 bolt and SF 14 bolt. I wonder where I can find some 1 tons. Hmmmmm

03-27-2002, 11:06 PM	#9
70-K10-292 Registered User Join Date: Apr 2000 Location: Peru,NY Posts: 183	Dumb Question is your TCS Transmission Controlled Spark still hooked up or is it disconnected? ------------------ 1970 K-10 292 Longbed stepside powersteering but manual brakes!Factory step bumper,Deluxe gauges no Tach 4 speed manual 1 out of 464 made with protectoplate intact.Its basic for a farm truck __________________ Where Am I ? How did I get Here ? 1970 K-10 292 Longbed stepside (now a stakerack)powersteering ,Factory step bumper,Tow Hooks,Deluxe gauges Tach & Throttle, 4 speed manual 1 out of 464 made with protectoplate intact .

03-28-2002, 09:30 PM	#10
JIMs70GMC user # 2756 Join Date: Jun 2001 Location: Chesapeake, Virginia Posts: 4,612	70-K10-292, do not have TCS, that's on auto tranny's only, right? 704X4, checked timing today and your right was 4 degrees further advanced. Retarded it and idle is back at 800(approx). Have not replaced the fuel filter will do that after I replace the front shoes(failed state inspection). Is 32,000 miles on the front shoes good wear? Previous owner replaced them just before I bought the truck. Update: replaced fuel filter, that was the problem. Thanks, ------------------ 1970 GMC K25 Custom Chesapeake, VA My 70 GMC or Webshots My 70 GMC on webshots [This message has been edited by JIMs70GMC (edited March 29, 2002).] __________________ 1970 K25, 8' stepside bed 350/465/205 44 up front, 60 in the rear 4.10s rolling on 33" Dunlop MTs 1986 K5, 350/465/208 Dana 60/14 bolt from a cucv 36" Super Swampers TSL/SX 1983 K20 w/ CUCV axles, 350/700R4/208 sitting on 37" Goodyears 1986 M1031 6.2 diesel, TH400/NP205 locker in the rear and a LS in the front, all stock for now..... 1986 K30, 350/400/205 dana 60 and 14 bolt. I kept the drivetrain. Body/bad and chassis are gone. 1981 K30, 350/465/205 dana 60 and dually 14 bolt. Has a G80, and a flat bed. Going to replace the flat bed. 1985 K20, 350/400/208 10 bolt and SF 14 bolt. I wonder where I can find some 1 tons. Hmmmmm



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