Author Topic: truck stalling/idling rough  (Read 1614 times)

Offline cochese

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truck stalling/idling rough
« on: July 06, 2007, 05:27:01 PM »
hello -  i recently joined the site.  i just got an 86 c-10 lwb, 305 v-8.  i'm trying to get it running well enough to be a relatively dependable daily driver.  i'm having an issue right now with the truck wanting to stall when i start it up. 

background info - since the ruck is an 86, the original carb had a bunch some extra emissions stuff.   the previous owner replaced the carb with another q-jet without some of the emissions sensors,etc. - for one, there is a dangling wire that i think  is from the coolant temp. sensor.  i'm wanting to know if this will lead to any problems or performance losses.  if so, what options do i have other than trying to find the carb that originally came with the truck.  i would consider an aftermarket carb.

now on to my current problem -
when i start the truck, i let it warm up (how long should this be?) it idles fine in fast idle.  then i hit the throttle lightly to disengage the fast idle.  when i do that, the idle speed goes down, but then starts to stumble a bit.  when i put it into reverse (most noticeable in reverse) , the truck starts idling down until it eventually dies unless i give it some throttle.  if i get moving right after i shift, i can get moving.  same if i get into drive quickly.  when i'm at a light, it stumbles but won't die (yet).  however, sometimes i don't have this problem - idles fine at lights, no stumbling.  one thing that i have noticed, is that the oil pressure gauge jumps around as it stumbles.  i don't know if one thing has anything to do with the other, but it seems wierd that the oil pressure drops as the idle goes down - ???

i hope this isn't too long.  i'm just looking for suggestions.  it may be that i need a carb rebuild, or new carb.  recently had it at a mechanic who said the idle was high and adjusted it down some.  seems like it started happening around the same time.  any help is much appreciated.  thanks.
1986 c-10
305 5.0 V-8

Offline Blazin

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Re: truck stalling/idling rough
« Reply #1 on: July 06, 2007, 08:30:40 PM »
Welcome to the board from New Hampshire.
 If it started happening after he adjusted the idle down I would turn it back up a some and see if it continues before anything else.
Some people are like Slinkies. Not really good for anything, but they still bring a smile to your face when you push them down a flight of stairs

Offline cochese

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Re: truck stalling/idling rough
« Reply #2 on: July 07, 2007, 05:55:18 PM »
thanks for the quick response.  i tried adjusting it back up as suggested, but the idle still stumbles/fluctuates and as it does - the oil pressure gauge goes down and back up.  could it be something dealing with the sending unit?  thanks.
1986 c-10
305 5.0 V-8

Offline dumbucket1

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Re: truck stalling/idling rough
« Reply #3 on: July 07, 2007, 06:40:07 PM »
sounds an awful lot like maybe vacuum leaks or the carb is just plain shot and needs a rebuild.

The oil pressure will naturally go up or down with the rpms especially on a well worn engine.
Chevy and GMC trucks ranging from 1973 to 2007

Offline Blazin

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Re: truck stalling/idling rough
« Reply #4 on: July 07, 2007, 06:48:59 PM »
My 86 2500 with a 350 the choke runs through the oil pressure sending unit. I had problem with the sending unit not working and it made the choke in-op too. I by passed it in the wiring and put in after market gages.
Some people are like Slinkies. Not really good for anything, but they still bring a smile to your face when you push them down a flight of stairs