1986 suburban can't figure out the sputter

[Herb S]

OK I am new, I have a 1986 k10 suburban 350 carb. When I first start it the idle fluctuates till it runs for awhile. Has the auto choke on it. Then once she warms up and idles down vibrates in park and at stops, give it alittle gas and it smoothes out, but if you nail it it will hesitate. Shifts fine normale driving, but when you try to get on it alittle heitates before kicking down. Is this a fuel pump/filter problem, or maybe carb? Also what is the max tire I can put under it without lifting? Has 31 105 R15 now but they just don't fill the hole enough for me.

 

[nad]

Sounds to me like your carb needs to be tuned. And if it's a Q-jet, you'll probably have fits getting it 'just right'. On my old K5, I finally just gave up and took it to a shop to have it tuned. Then again, I don't have any experience with carb'd applications, so it was a bit much for me to figure out. Seemed like everything I did ended up making it worse, or fixing the hesitation, but having high idle, etc...

 

[ryoken]

OK I am new, I have a 1986 k10 suburban 350 carb. When I first start it the idle fluctuates till it runs for awhile. Has the auto choke on it. Then once she warms up and idles down vibrates in park and at stops, give it alittle gas and it smoothes out, but if you nail it it will hesitate. Shifts fine normale driving, but when you try to get on it alittle heitates before kicking down. Is this a fuel pump/filter problem, or maybe carb? Also what is the max tire I can put under it without lifting? Has 31 105 R15 now but they just don't fill the hole enough for me.

welcome.....

you can probably fit a 33.. check the "how will my truck look" sticky thread in the Garage...


as to the carb.. i'm assuming it's the CCC quadrajet.. first, put a filter in, no reason not to put a new fuel filter in a "new to you" vehicle... and yeah, it could be a # of things.. schmootz in the carb bowl, etc.... my immediate guess might be an issue with the idle circuit...

do yourself a BIG favor and pick up the "Bible" of quadrajets, Doug Roe's Rochester book....

 

[Herb S]

I have been putting the cheap gas in the truck. That is all I ever ran in My scottsdale quad cab and never had a problem I think you could have pissed in that tank and she would have ran fine. But yesterday I put the good stuff in it with a can of octane booster and it helped the fluctuation but still has hesitation when you mat it. More so while turning then when going straight. I will change fillter and I do belive it is a qjet carb. Also when I remove the air filter it was gas soaked.

 

[ryoken]

I would give it a healthy cleaning with a seafoam shock treatment in the tank... i like a 2 can shot... helps clean out the bowls and orrifices... a "rebuild in a can" as i like to call it.. and a liberal douching with carb cleaner.. to make sure all the linkage is working correctly, accelerator pump, throttle plates, etc..

one recommendation i usually make after a good carb douching with carb cleaner, is to change your plugs after... plugs are never the same after all that carb cleaner is burned thru em it seems...

 

[nad]

If the carb and area around it is gas soaked, you may have a fuel leak somewhere.