Have to crack throttle to start when cold

[1993GMCSierra]

Hi all,

1993 Sierra, 305 TBI, 135K. Truck runs well, but when it's "cold", aka sitting for hours/overnight, if I turn the key, it will start and die. In order for it to actually start and run, I have to crack the throttle just a tad with my foot. Then it starts, and "catches" and runs fine. When truck is slightly warm/operating temp, it will start with no assistance each time, but not when cold. Any ideas? New fuel filter a year (3K miles) ago, fuel pump seems to work just fine when the truck is running.

 

[twomanymontes]

Sounds like a dirty or stuck Idle Air Control motor. Try removing it and cleaning it.

 

[IOWNJUNK]

Does pump run longer on the initial start than it normally does? Might be getting air in the lines when it sits for long periods, may not have anything to do with temp. Check for a fuel leak in the fuel lines, doesn't take much of a leak to fill lines with air overnight.

 

[1993GMCSierra]

No fuel leaks, I just turn the key and go, I don't "prime" the engine. Never came across anything that would be evidence of this.


I get good discounts on OEM parts at work, and I may just replace the IAC. Is there a relearn procedure for trucks this old, or is it simply a R&R and go deal? The reason I lead to replacing it, is because last year I took it out to clean it, and I remember I accidentally pulled the pintle out of the IAC assembly. I stuck it back in there, and it seemed to work fine, but it could be causing an issue now.

 

[IOWNJUNK]

I would replace IAC and see, just because you had an issue with it in the past. I never crank mine till the pump shuts off out of habit, the TBI 350 in my K5 would not start if I just put key in and tried to crank. Didn't matter if it was first or 5th time, it would start then shut off. Now I do it with all my vehicles. Just habit.

 

[Scrufdog]

Replace the IAC and let the pump prime for at least a couple seconds, never hurts. I've driven diesels for many years, so waiting to start is a habit at this point.