'79 250ci idle speed adjust - truck stalls when coasting - The 1947 - Present Chevrolet & GMC Truck Message Board Network

J1MMY · 01-13-2015, 03:25 PM

Hi All

Just bought a '79 C10 shortbed w/250ci and TH350. I bought it as a road going project and it drives well except for one thing - once youre off the throttle and are coasting to a junction, it stalls as you brake to a halt. Everything else seems fine, auto choke is fine cold starting, Tickover settles when the engine warms up (and it will tick over all day long), drives smoothly through the gears.

The I6 is only temporary until I find a V8 (I'd prefer a 292 to convert to efi but no chance of finding one here in the UK) but I'd still like to use the truck in the meantime.

Any help appreciated. Thanks for reading.

Bigstevex4 · 01-13-2015, 04:22 PM

automatics lack eng braking should be like an decelration solinoid that gently bring it down to idle or set idle higher

Your41Plague12 · 01-14-2015, 08:09 AM

Could be your torque converter too.

Dead Parrot · 01-14-2015, 01:41 PM

Language question - is tickover an UK term for idle?

Does it have AC? If so, is the defrost on? That will run the compressor which can drag a 6 cylinder down. There should be an AC idle solenoid to boost idle when the compressor kicks in. Those sometimes vanish when a PO 'cleans up' an engine compartment.

J1MMY · 01-15-2015, 03:31 PM

Nope, no air con, no PAS, base model spec.

Oh sorry, yes - Tickover = Idle. I'm doing my best to use your terminology but the odd thing might slip

Dead Parrot · 01-15-2015, 08:18 PM

I like hearing the different terms for things. I learn things that way. I have heard a two word variation here - "It is barely ticking over."

You mentioned braking causing it to stall. If you just let it coast to a stop, no braking, does it keep running? If power brake, maybe there is vacuum leak that stalls it. Does it stall if you do the final stop with the park/emergency brake? Can you replicate the stalling with the truck stationary? Wondering if you might have a bit of fuel sloshing in the carburetor.

For that matter, do a good check of all the vacuum hoses. A small leak can cause big problems.

The simple solution might be to just up the idle/tickover speed a bit.

J1MMY · 01-17-2015, 01:41 PM

I'll have a go at using terminology from both sides of the pond then - there are quite a few differences!

All vacuum pipes are fine.

I adjusted the throttle stop screw which has sorted the issue. The truck seems to be running rich and is returning around 12 imp. MPG (that's about 10 of your MPG!).

Maybe I should rename this thread with a catchy non Specific title! :P

01-13-2015, 03:25 PM	#1
J1MMY Registered User Join Date: Aug 2009 Location: Wiltshire, UK Posts: 157	'79 250ci idle speed adjust - truck stalls when coasting Hi All Just bought a '79 C10 shortbed w/250ci and TH350. I bought it as a road going project and it drives well except for one thing - once youre off the throttle and are coasting to a junction, it stalls as you brake to a halt. Everything else seems fine, auto choke is fine cold starting, Tickover settles when the engine warms up (and it will tick over all day long), drives smoothly through the gears. The I6 is only temporary until I find a V8 (I'd prefer a 292 to convert to efi but no chance of finding one here in the UK) but I'd still like to use the truck in the meantime. Any help appreciated. Thanks for reading. Last edited by J1MMY; 01-13-2015 at 03:26 PM. Reason: 'Shortbed' not 'Shortbread'!

01-13-2015, 04:22 PM	#2
Bigstevex4 Registered User Join Date: Oct 2014 Location: Spearfish South Dakota Posts: 407	Re: '79 250ci idle speed adjust - truck stalls when coasting automatics lack eng braking should be like an decelration solinoid that gently bring it down to idle or set idle higher

01-14-2015, 08:09 AM	#3
Your41Plague12 Registered User Join Date: Dec 2010 Location: Pittsburgh, PA Posts: 1,009	Re: '79 250ci idle speed adjust - truck stalls when coasting Could be your torque converter too. __________________ Steve Member of the Foot Pedal Club '83 Chevy K20: 6" Rough Country, 3" Performance Accessories BL, Bushwacker Cutouts, 38x15.50 Mickey Thompson Baja Claws, 350 HP 350 crate engine from Jegs, Turbo 400

01-14-2015, 01:41 PM	#4
Dead Parrot Registered User Join Date: Aug 2012 Location: Oklahoma City, OK Posts: 2,518	Re: '79 250ci idle speed adjust - truck stalls when coasting Language question - is tickover an UK term for idle? Does it have AC? If so, is the defrost on? That will run the compressor which can drag a 6 cylinder down. There should be an AC idle solenoid to boost idle when the compressor kicks in. Those sometimes vanish when a PO 'cleans up' an engine compartment.

01-15-2015, 03:31 PM	#5
J1MMY Registered User Join Date: Aug 2009 Location: Wiltshire, UK Posts: 157	Re: '79 250ci idle speed adjust - truck stalls when coasting Nope, no air con, no PAS, base model spec. Oh sorry, yes - Tickover = Idle. I'm doing my best to use your terminology but the odd thing might slip

01-15-2015, 08:18 PM	#6
Dead Parrot Registered User Join Date: Aug 2012 Location: Oklahoma City, OK Posts: 2,518	Re: '79 250ci idle speed adjust - truck stalls when coasting I like hearing the different terms for things. I learn things that way. I have heard a two word variation here - "It is barely ticking over." You mentioned braking causing it to stall. If you just let it coast to a stop, no braking, does it keep running? If power brake, maybe there is vacuum leak that stalls it. Does it stall if you do the final stop with the park/emergency brake? Can you replicate the stalling with the truck stationary? Wondering if you might have a bit of fuel sloshing in the carburetor. For that matter, do a good check of all the vacuum hoses. A small leak can cause big problems. The simple solution might be to just up the idle/tickover speed a bit.

01-17-2015, 01:41 PM	#7
J1MMY Registered User Join Date: Aug 2009 Location: Wiltshire, UK Posts: 157	Re: '79 250ci idle speed adjust - truck stalls when coasting I'll have a go at using terminology from both sides of the pond then - there are quite a few differences! All vacuum pipes are fine. I adjusted the throttle stop screw which has sorted the issue. The truck seems to be running rich and is returning around 12 imp. MPG (that's about 10 of your MPG!). Maybe I should rename this thread with a catchy non Specific title! :P



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.