Stalling

[kaycee]

2001 5.3 Silverado truck was having a hard time starting about the first 5 seconds it would struggle to get idle on cold start. Noticed volt meter was weak at this time did a voltage test and pointed me to bad battery ,replaced battery.ONCE the volts got up to 14 it idles like it suppose to ,runs good rest of day.sometimes I come to stop light and it will almost die volts are up though. Changed plugs and wires starts better but still has the weak idle and at times and the cold starts are better not like it should be but better. Where do I look no engine light or codes truck runs great down the road and will start great after the first cold starts, fuel pump,bad ground, IAC solenoid don’t want to throw parts at it but that’s where I am at now. NEW fuel filter 2k miles and the pump has 10k

[hatzie]

What's your fuel pump pressure on cold start?
Are you getting any misfires on individual cylinders?
What kind of oddities do you seeing or not seeing in the long-term and short-term fuel trims?

[kaycee]

Ok no codes any misfires basic scanner tool ,Right at 50lbs. On start up ,cleaned the mass air flow sensor and throttle body today .Truck runs great other than the cold start and the intermittent idle at stop.

[Killer Bee]

symptoms sound like b/o fuel pressure regulator, common issue

simple test - pull the vacuum line and look for fuel, if wet diaphragm is bad

cheap and easy replacement, cross your fingers

good luck!

[kaycee]

No it Wasn’t wet ,I YouTubed it yesterday and been checking all the easy stuff also found a guy that experienced the same symptoms.He looks at all the fuel trims and such on his scanner turns out he ends out changing cam sensor. Wouldn’t this throw a code ?

[Killer Bee]

yah, most b/o sensors will trigger code(s) because they provide data to ecm, when irregular or out of parameters the ecm will generally report a cel. this doesn't mean the IAC, CPS, or others are not malfunctioning, however they typically trigger codes

something else that sort of matches symptoms could be a dirty throttle body, your idle quality, throttle response and stability may benefit from proper cleaning and calibration

checked for vacuum leaks?

how long have you owned this '01?

how many miles on it?

any recent engine work?

stock or does it have any mods?

symptoms start suddenly, possibly surrounding some sort of event or gradually?

[kaycee]

I have owned since 2002 currently at 204 k miles no mods ,no engine work done to it.I did clean MAF and throttle body when I changed plugs /wires will clean again and see if it clears up

[kaycee]

Fuel pressure. 50 lbs bleeds off in 45 min. Redo clamp off return line bleeds off same amount of time will pinch off both lines and hopefully won’t bleed off pointing to injector if it does. Am I heading in the right direction ?

[Killer Bee]

still sounds like fuel pressure regulator, not sure if they always leak through diagram if faulty, previous wet vacuum line test may be a false negative. hate tossing parts but very cheap and easy replacement

slow bleed could also be anti drain back check valve, in the pump assembly I believe. how old/miles on it, is it due? if so, highly recommend oem delco unit

do you have a diag tool that provides cylinder contribution test? something I'd do before replacing injectors

sounds like you're getting closer, good luck!

[kaycee]

Been kinda busy lately but back at it,decided to replace press, regulator,sounds easy right.After removing old one noticed the little o-ring was still in the housing removed it and managed to push it into the fuel rail. I tried to fish it out but no luck.Can I leave it in there or do I remove the trail and get it out ?

[kaycee]

FYI don’t do this as it is a PITA ,got it fished out this a.m. it’s always nice to do when it’s 20 * out and a brisk 40 mph wind .

[Killer Bee]

yah, that o-ring would need to come out, glad you were able to get to it. lesson learned I guess.

that's something second nature to mechanics, always cautious of small parts and places they'll run off into.

be careful in foul weather, don't make yourself sick over it.

sooo, new regulator make any change? if you have a mityvac, you can test the old one to see if it leaks, maybe only under high vac where the dribble test doesn't catch it at idle.