Hesitation/Surging problem - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Iowa · 02-13-2003, 11:15 AM

I have an 84 chevy 3/4 ton 2 wheel drive 350 auto. 1st problem is mainly when cold but even when its at operating temp it will hesitate/surge. rebuit carb, problem still there. 2nd problem is vibration in drive train from 35 to 40 mph. noticed this after changing bad center bearing. All u-joints good, split drive shaft can only be put together one way. can someone please help here? TIA

apstguy · 02-13-2003, 01:16 PM

Welcome to the board! When cold & the choke is still engaged, it will surge. Shouldn't when it is warm. Maybe the choke is sticking?

Try checking the flexplate (automatic check if vibration), get tires ballenced, get it aligned, ????

Iowa · 02-13-2003, 03:04 PM

Flex plate? where and what is it. The tires were balanced, come to think of approx. at same time as center driveshaft bearing. I do need to get an alignment though. Thanks for the reply.

79BIG10 · 02-13-2003, 07:26 PM

Welcome

The flexplate is the same as a flywheel on manual trannys. It's the part that meets the engine rear to the gtranny front. The wheel/plate mounts to the engine's crankshaft and when the starter engages it grips the teeth along the edge and turns the wheel/plate to crank the engine.

I would check tires out of balance as well as weights fallen off of the driveshaft.

Iowa · 02-16-2003, 07:49 PM

Found hesitation to be fuel pump just thought i would let you know. First time a fuel pump has went bad like that i have known. Would the flex plate create vibration even if put in neutral? Thanks for replying to my problems.

apstguy · 02-17-2003, 01:26 AM

The flexplate rotates any time the truck is running - so yes it can cause vibration in neutral. Flexplates are attatched to the torque converters in front of the transmission.

PHOENIX · 02-17-2003, 01:22 PM

Do you have an EGR valve (located on the intake manifold, near the back rear passenger side of the carb, emissions component)? If you do, try unhooking it from the egr (bell shaped, one vacuum line). Then plug the line and cap the EGR. Take it around the block a few times and see if that fixes it. If it does you either need a new EGR valve ($50-$75 new from GM dealer, can get cheaper at checker) or something wrong with vacuum port. Maybe hooked to wrong vacuum port or no getting the correct amount.

Did any 3/4 tons come with EGR valve?

02-13-2003, 11:15 AM	#1
Iowa Registered User Join Date: Feb 2003 Location: Iowa Posts: 6	Hesitation/Surging problem I have an 84 chevy 3/4 ton 2 wheel drive 350 auto. 1st problem is mainly when cold but even when its at operating temp it will hesitate/surge. rebuit carb, problem still there. 2nd problem is vibration in drive train from 35 to 40 mph. noticed this after changing bad center bearing. All u-joints good, split drive shaft can only be put together one way. can someone please help here? TIA

02-13-2003, 01:16 PM	#2
apstguy LED King Join Date: Jan 2003 Location: Sacramento, CA Posts: 2,087	Welcome to the board! When cold & the choke is still engaged, it will surge. Shouldn't when it is warm. Maybe the choke is sticking? Try checking the flexplate (automatic check if vibration), get tires ballenced, get it aligned, ???? __________________ Tyler 1985 C10 305 w/ Bowtie OD TH700R4 3.42 LSD 202,000 miles 2006 Ford Focus ZX3 5-speed Stick 2016 Chevy Spark EV Gone: 2002.5 VW GTI 24v VR6 Gone: 2008 VW R32

02-13-2003, 07:26 PM	#4
79BIG10 I'm back with 2nd truck! Join Date: Feb 2002 Location: Texas Posts: 3,774	Welcome The flexplate is the same as a flywheel on manual trannys. It's the part that meets the engine rear to the gtranny front. The wheel/plate mounts to the engine's crankshaft and when the starter engages it grips the teeth along the edge and turns the wheel/plate to crank the engine. I would check tires out of balance as well as weights fallen off of the driveshaft. __________________ 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

02-17-2003, 01:26 AM	#6
apstguy LED King Join Date: Jan 2003 Location: Sacramento, CA Posts: 2,087	The flexplate rotates any time the truck is running - so yes it can cause vibration in neutral. Flexplates are attatched to the torque converters in front of the transmission. __________________ Tyler 1985 C10 305 w/ Bowtie OD TH700R4 3.42 LSD 202,000 miles 2006 Ford Focus ZX3 5-speed Stick 2016 Chevy Spark EV Gone: 2002.5 VW GTI 24v VR6 Gone: 2008 VW R32

02-17-2003, 01:22 PM	#7
PHOENIX Registered User Join Date: Oct 2002 Location: Phoenix, Arizona Posts: 4,703	Do you have an EGR valve (located on the intake manifold, near the back rear passenger side of the carb, emissions component)? If you do, try unhooking it from the egr (bell shaped, one vacuum line). Then plug the line and cap the EGR. Take it around the block a few times and see if that fixes it. If it does you either need a new EGR valve ($50-$75 new from GM dealer, can get cheaper at checker) or something wrong with vacuum port. Maybe hooked to wrong vacuum port or no getting the correct amount. Did any 3/4 tons come with EGR valve? __________________ * AVOID: LOPER'S PERMORANCE / LOPERSPEED.COM OF PHOENIX, AZ & COTTMAN TRANSMISSION *

02-13-2003, 03:04 PM	#3
Iowa Registered User Join Date: Feb 2003 Location: Iowa Posts: 6	Flex plate? where and what is it. The tires were balanced, come to think of approx. at same time as center driveshaft bearing. I do need to get an alignment though. Thanks for the reply.

02-16-2003, 07:49 PM	#5
Iowa Registered User Join Date: Feb 2003 Location: Iowa Posts: 6	Found hesitation to be fuel pump just thought i would let you know. First time a fuel pump has went bad like that i have known. Would the flex plate create vibration even if put in neutral? Thanks for replying to my problems.

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