GM 5.3L Stumbles When Cold

crash2 · Jan 27, 2009

tobyw said:
I put a new battery in this summer, no indications that its failing, so I think I'm covered there... Never washed the engine either, its the 100% mommy mobile and stays pretty clean overall. A little dusty under there but no grime or anything.

So Crash - you think there is more going on than a dirty intake trac? I probably won't have time to clean it all up until this weekend, so I won't have much to report between now and then... Anything else I can check or do?

I would clean the throttle body anyways but I am pretty sure you have other issues. As far as what could be wrong--hard to tell since there are a # of things that can cause it.. One thing I have seen a few times is the intake plenum seals leaking vacuum but you typicly get a miss when warm too/rough idle. But the leak could be just enough to where it only shows when cold.

Start it and take some Brake clean and spary some down along the runners (inbetween the plenum/head) and see how it reacts.

tobyw · Jan 27, 2009

crash said:
I I am pretty sure you have other issues.

Crap...

crash said:
Start it and take some Brake clean and spary some down along the runners (inbetween the plenum/head) and see how it reacts.

Will do... I should have time to try that tonight, so I'll report back if I get to it.

wazz · Jan 27, 2009

Sounds like with a P0300 you may want to check fuel PSI if that intake seal docent seem to be leaking.

tobyw · Jan 27, 2009

wazz said:
Sounds like with a P0300 you may want to check fuel PSI if that intake seal docent seem to be leaking.

I can do that pretty quickly as well... What's the acceptable range?

crash2 · Jan 27, 2009

tobyw said:
I can do that pretty quickly as well... What's the acceptable range?

50-55 psi But I don't suspect that... But if you can easily check it might as well rule it out...

tobyw · Jan 27, 2009

Well, I can screw on the whip for the FPG and watch the it as I'm dousing the intake with Brake Clean as the engine warms up, so I guess I can kill two birds with one stone here?

crash2 · Jan 27, 2009

tobyw said:
Well, I can screw on the whip for the FPG and watch the it as I'm dousing the intake with Brake Clean as the engine warms up, so I guess I can kill two birds with one stone here?

Ya---sure :awesomework:

wazz · Jan 28, 2009

:beer:

if you can jump the FP relay is best, but while running should yield the similar results.
Yours is 55-62 so if it hits 55 yours is fine, if it only hits 50 its not working good

edit: I have had a rig like yours not start but barely some times at 51PSI

tobyw · Jan 28, 2009

Did not get a chance to work on it last night, probably going to have to wait for the weekend now

At any rate, I was thinking about it on the way to work this morning, and the idea of a vacuum leak that seals up at warmer temps bothers me for sure. However, the issue goes away with increased RPM even when it's still dead cold... I realize increased RPM usually changes vacuum readings, but a leak is a leak, right? What I'm getting at is, does it really sound plausible?

DEANS4.3TOYO · Jan 28, 2009

some of these vehicle have a reflash for this problem,but you need to find someone with a scanner not a dumbass code reader, those things are the stupidest miss informing thing made schucks sells code readers so you can throw parts at your rig. clean the throutle body and see if it goes away and use the right cleaner.If it doesn't find a scanner and pull codes wright them down and post them the way they are from the scanner.good luck.:corn:

tobyw · Jan 28, 2009

Fair enough...

Possibly stupid question: are these scanners universal? I know a couple Ford techs that probably have access to such an animal, but I don't know if it would work on a GM product?

wazz · Jan 28, 2009

huh,, learned something new

This TSB # for the P0300

05-06-04-029A

tobyw · Jan 28, 2009

Huh, very interesting... Too bad they won't cover TSB work once it's out of warranty :booo:

DEANS4.3TOYO · Jan 28, 2009

yes the scanners are universal if you were close to snohomish i have a snapon scanner and a vantage that would do the trick.

crash2 · Jan 28, 2009

I prefer a Tech-2

wazz · Jan 29, 2009

crash said:
I prefer a Tech-2

yeah what ever, lol

I wish all rigs had Tech2 ability
:fawkdancesmiley:
for now my OTC Genesis will have to :corn:

crash2 · Jan 29, 2009

wazz said:
yeah what ever, lol

I wish all rigs had Tech2 ability
:fawkdancesmiley::corn:

Why I have my backup snap on scanner,lol

wazz · Jan 29, 2009

crash said:
Why I have my backup snap on scanner,lol

my old skool snapy-tom brick updated to 1999 has save my ass plenty over the = still a great tool Genesis, I hear ya though

there is no all in 1 unit fo sure :;

tobyw · Jan 29, 2009

Well, I had a couple minutes to work on it last night before we ran out the door... I had the wife start it up, and waited for it to idle down (about 10-15 seconds), and once it got below about 800RPM, sure enough it started to shake and studder. I gave it a healthy bath in brake cleaner all around the intake/heads, with no change in RPM or any reaction at all that I could tell... As usual, if she would rev it up to about 1000RPM, it would smooth right out.

So, I guess that is good news regarding a possible leak, but it takes me back to cleaning the intake trac this weekend and waiting to see how that goes...