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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: gold84gmc on January 21, 2009, 03:59:32 pm

Title: hesitation/stumble when pushing gas too much in cold weather
Post by: gold84gmc on January 21, 2009, 03:59:32 pm
i have an 84 gmc with a 350 with a q-jet carb...in cold weather and sometimes in warm weather if i push the gas too much the engine starts to hesitate or stutter and it doesnt want to go unless i let go of the gas some...but if i put it in neutral or park and rev it up its fine...does anyone know what could be causing this
Title: Re: hesitation/stumble when pushing gas too much in cold weather
Post by: Blue 82 on January 21, 2009, 05:17:28 pm
Check your accellerator pump shot
You may not be getting enough at the right time
Title: Re: hesitation/stumble when pushing gas too much in cold weather
Post by: gold84gmc on January 21, 2009, 05:42:07 pm
i tried checking that and i can hear and smell the gas but i couldnt see any(i dont know if its becuase i didnt have a light to look in the carb)
Title: Re: hesitation/stumble when pushing gas too much in cold weather
Post by: Unofficial on January 21, 2009, 07:37:17 pm
I have the exact problem. It happens very often in the winter and only sometimes when it's warm out. I have a TBI though.
Title: Re: hesitation/stumble when pushing gas too much in cold weather
Post by: choptop on January 21, 2009, 09:29:47 pm
I think the problem may have to do with the cold engine. Everyone I had would do the same thing until the engine got up to operating temp. The intakes and carbs on these dont seem to atomize the fuel very well when its cold. I figure the tbi would have less trouble, but it does still have to go through the intake. I imagine the fuel condenses in the cold intake. It wont do it in neutral because there isnt much load on the engine. I am not sure of this, its just what I have always thought. Every bigblock I had would not hardly move until it was warn. The small blocks didnt seem as bad, but still did it.
Title: Re: hesitation/stumble when pushing gas too much in cold weather
Post by: gold84gmc on January 22, 2009, 05:24:59 am
mine does it even when the engine is up to normal temp....it just does it everytime i drive it in cold weather and sometimes in warmer weather
Title: Re: hesitation/stumble when pushing gas too much in cold weather
Post by: choptop on January 22, 2009, 07:50:13 am
Check your accellerator pump shot
You may not be getting enough at the right time

+2 check timing as well
Title: Re: hesitation/stumble when pushing gas too much in cold weather
Post by: Unofficial on January 22, 2009, 11:43:17 am
mine does it even when the engine is up to normal temp....it just does it everytime i drive it in cold weather and sometimes in warmer weather

Again, we have the exact same problem. I'll be up to operating temperature and it will still do it. And just like you, it happens in warm weather, but not as often. Sometimes it will pop and sputter too. You wouldn't think it would do this because I have TBI though...
Title: Re: hesitation/stumble when pushing gas too much in cold weather
Post by: gold84gmc on January 22, 2009, 02:08:50 pm
i know the timing is off but if it was the timing causing this then wouldnt it do it everytime...not just in the cold and sometimes in the warmth
Title: Re: hesitation/stumble when pushing gas too much in cold weather
Post by: Donut on January 23, 2009, 04:54:11 am
If your talking last weeks cold, I was hesitating to. :)

I wouldn't rule out the choke either.  Not fully opening or not functioning at all could cause this.  I just hooked mine back up for this same reason.

Could also be icing up on you.
Title: Re: hesitation/stumble when pushing gas too much in cold weather
Post by: gold84gmc on January 23, 2009, 05:43:31 am
it did do it the worst last week but it does it a lot if its below maybe 40 degrees or so...and does it rarely when its warmer...and i tried holding my choke open while driving because i was thinking maybe the choke is closing but it stays fully open
Title: Re: hesitation/stumble when pushing gas too much in cold weather
Post by: 82TARDIS on January 23, 2009, 06:38:39 am
I know I'm a newbie here, but I was having a similar problem back in November with my '82 C10.  I finally found a vacuum line that had slipped off...put it back on, and problem was solved.  Of course, that was on a little 250, but your 350 probably has the same problems, only bigger  ;)
Title: Re: hesitation/stumble when pushing gas too much in cold weather
Post by: gold84gmc on January 24, 2009, 06:54:34 am
i looked for bad vacuum lines or ones that fell off and didnt find any....even thought the TRC (throttle return control) has 2 vacuum line connections on it and one of them broke off a while ago...i dont know if thats the problem or not
Title: Re: hesitation/stumble when pushing gas too much in cold weather
Post by: Prong on January 25, 2009, 04:33:05 pm
Do you have an open air cleaner? I've found those things are problematic for me in the cold(er) weather.
Title: Re: hesitation/stumble when pushing gas too much in cold weather
Post by: gold84gmc on January 25, 2009, 05:45:58 pm
what do you mean?...do i have the lid flipped upside down?....if thats what your asking then no i dont
Title: Re: hesitation/stumble when pushing gas too much in cold weather
Post by: gold84gmc on January 25, 2009, 05:47:36 pm
i was looking at some pics of q-jets and i saw that the choke pull off has a rod connected to it going to the choke mechanism....i dont know if mine ever had that but as of right now mine does not have anything connected to the choke pull off....is this what could be causing my problem?
Title: Re: hesitation/stumble when pushing gas too much in cold weather
Post by: gold84gmc on January 28, 2009, 02:44:26 pm
i brought my truck to a garage to have my carb fixed and they looked at the fuel filter and said it was pretty dirty so they put a new one and said it went fine.....i replaced it last spring so i didnt think it wouldve been that dirty...thanx everyone for your help