I dunno..65ish i think...see if you can borrowa vacuum pump and make sure the regul;ator holds vacuum

 

It's your fuel pressure regulator. I have a 5.3 and I've replaced mine once already. It's doing it again now. I waited longer then I probably should have the first time I replaced it and after about a year I ended up having to replace the fuel pump as well. These are the symptoms you will see: At first the truck starts rough, idleing low enough where it feels like it will die. After a while The truck won't turn over on the first shot, it will turn on the second after the fuel pump engages. Then on colder days when you start it and put it in drive it will chug and idle so low it either will die or the idle will finally smooth out. Then you get to a stop sign or light and the idle fluctuates from 500-1200rpms when you have your foot on the break and it will almost die. If you put it in neutral and give it abit of gas, around 1000rpms it will stay running. Does this sound like a similiar problem? It's the fuel pressure regulator. MSRP is $112.46. If you go to GMpartsdirect.com it's $58.47 Part # 890174538901745. I have the '99 K1500 5.3l Silverado Z71 new body style, any mechanic you talk to will tell you this part is notorious for failing

 

I've never heard of this problem until now and this is my second Silverado preceeded by a 4.3 S10. There has got to be a specific cause for failure.
My brother in law replaced his on his camaro with a new unit from jegs/summit for $45/$65. I know it was well under $100.

 

My 2002 5.3 does the same thing at times, usually when it iscolder in the mornings. Fuel Reg sounds about right. Cracker did you mean to say 4.3 S10? The 4.6 is a Ford Motor

 

The only symptom I'm having right now is every once in a while when I start it it will idle REALLY low for about 2 seconds. But it doesn't do it every time. I drove it to work and checked the vacuum line when I got there and it was dry. I'll see about getting a vacuum pump to put on it. I'm around enough mechanic people I'm sure I can find someone. Heck if it's cheap enough at work I may just buy one. I work at O'reilly Auto parts now so I may be able to get it REAL cheap.

 

Would it still be the same problem if the engine was at normal operating temp?

 

Yeah, temp doesn't matter.

 

Good to know I'll check mine Sunday when I have the daylight.

 

Well this problem is getting a lot worse! The last time I started my truck it took 3 times to get it to start! I cranked it over once it turned over a few times, started, and stalled. I cranked it over again and it wouldn't start. I waited a few seconds then turned it over again and it took like 5-6 cranks before it would start. The fuel pump is whining and it runs great once it's on. No bogging or hesitation at all. I orded a new fuel pressure regulator. It's only $40 at work for me so I'm gonna try that and see. I hope to God it isn't the fuel pump. I can't afford to replace the fuel pump....[:@]

 

Well I replaced the fuel pressure regulator. I actually seemed to gain some torque! And so far it isn't having the starting problem but we'll see. I bet that was all it was cause it seems to be running a lot better than it was before. I never realized there was any kind of a running problem until now. Thanksfor pointing me in the right direction Steve!