Wife's 2003 Yukon just developed an issue this week (55k miles) - on COLD startup, it will stumble/studder like it's missing a few cylinders, and the MIL will flash. If you bump the RPM up a few hundred, to say 1200 or so, it smoothes right out, and once normal operating temps are reached, it runs like a champ. I'm off to purchase an OBD-II reader here in a few, but wanted to get some ideas as to what to look for here. This rig has been A-1 dependable and never given us a lick of trouble until this week. Thanks for any tips/ideas!!
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GM 5.3L Stumbles When Cold
- Thread starter tobyw
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Can't help you there, but just turned 188,000 on my 2000 Silverado with the 5.3, had to put a TPS in it last week, first problem I've had with it. Wouldn't idle below 1200, and wouldn't shift until around 22-2300 rpm. TPS cured that. Good Luck !!
Well, it's not storing any codes, as the OBD-II scanner tells me life is good... I guess since it only happens at cold start and then goes away once water temps get toward normal operating temps, it clears itself??
Since this issue goes away at normal operating temps, I am throwing out possiblities like fuel filter/regulator, tune items, and bad wires. It seems to be SOMETHING computer related at cold water temps that is telling the engine to run differently than it should.
I did a little bit of interweb searching and found a couple articles on similar issues, and it seems the common link is the MAF sensor... There was talk of cleaning it with favorable results, but no description as to how that task is accomplished? I don't really feel like making a multi-hundred dollar mistake, so can anyone point me in the right direction on cleaning the MAF on a 5.3L GM engine?
Since this issue goes away at normal operating temps, I am throwing out possiblities like fuel filter/regulator, tune items, and bad wires. It seems to be SOMETHING computer related at cold water temps that is telling the engine to run differently than it should.
I did a little bit of interweb searching and found a couple articles on similar issues, and it seems the common link is the MAF sensor... There was talk of cleaning it with favorable results, but no description as to how that task is accomplished? I don't really feel like making a multi-hundred dollar mistake, so can anyone point me in the right direction on cleaning the MAF on a 5.3L GM engine?
crazybluerider1
Well-Known Member
You are going to want to make sure you IAC is clean and also clean out the passages in you TB. A lot of the time a little clean up in the TB area will straighten these kind of problems out. I have had a couple of these trucks now and the have all benefited from clean up even the low milers.
crash2
-Oh no I picked a side-
Odd--the ses lamp flashes but doen't set any misfire codes :eeek:
The big problem I see is what crazybluerider stated--except I don't see the IAC ports being restricted---its critial around the throotle body..
So clean that real good and report back.
The big problem I see is what crazybluerider stated--except I don't see the IAC ports being restricted---its critial around the throotle body..
So clean that real good and report back.
crazybluerider1
Well-Known Member
For the mass air flow just carb and choke cleaner no contact. For the IAC light contact is ok but do not force it to move or anything. For the throttle body contact is fine.
crazybluerider1
Well-Known Member
The one the IAC ports were clogged on had 200k miles. It was my first new engine truck. Its still running strong.
Wife called a few minutes ago and it did not act up this morning?
Regardless, I will tear into the intake ducting this evening and give everything a good cleaning with some brake cleaner. We'll see what tomorrow morning brings...
Regardless, I will tear into the intake ducting this evening and give everything a good cleaning with some brake cleaner. We'll see what tomorrow morning brings...
zukkev
Cornfuzzled yet again...
Where is the smiley face for me scratching my head? Ahh yes, here it is... :scratchhead:
DEANS4.3TOYO
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i would look at the temp sensor personally it has two one for the gauge and one for the pcm you need a scanner that will monitor the data or watch the gauge and see if it is off a little. I have seen the egr valve mess with the idle at times check that also.:corn:
crash2
-Oh no I picked a side-
It would flag a code if it was. There are like 5 diagnostics ran on that sensor alone.
when u scan it...make sure and check for code history, and not current codes. since its running good when ur scanning it, its not going to show a CURRENT code.
does sound like a temp sensor...
is the coolant level low? have u checked it?
does sound like a temp sensor...
is the coolant level low? have u checked it?
P-0300
Since the high for today wasn't expected to get over 25* or so, I had the wife leave the rig outside all day. Once I got home, I plugged in the scanner and fired it up, and sure enough, I caught it in the act!!! I was greeted with a P-0300 code, which translates to "multiple cylinder misfires"...
Life caught up with me (kids...), so I didn't have time to tear it apart and clean it tonight, but does that code provide anyone with more useful info?
Since the high for today wasn't expected to get over 25* or so, I had the wife leave the rig outside all day. Once I got home, I plugged in the scanner and fired it up, and sure enough, I caught it in the act!!! I was greeted with a P-0300 code, which translates to "multiple cylinder misfires"...
Life caught up with me (kids...), so I didn't have time to tear it apart and clean it tonight, but does that code provide anyone with more useful info?
crash2
-Oh no I picked a side-
Odd. If the codes are not staying then you have more than one problem. One thing about OBD II even if there isn't a direct fault that created the code--the code still stays there since with OBD II there is no current/history codes.. Some codes take 30 cylces to even turn the ses lamp off and so many to have the code just go away..
As far as a p0300--that code isn't going going to tell you anything--except you have a missfire in more than one cylinder--its the data thats going to tell you what cylinders are the issue.....
As far as a p0300--that code isn't going going to tell you anything--except you have a missfire in more than one cylinder--its the data thats going to tell you what cylinders are the issue.....
2003
How old is the battery?
if it's original its junk by now.
If the battery goes low while starting it, the computer has no basics to work from.
Just an idea to work with, a 55K rig should have min. problems like this, so im thinking basics.
Also have you PSI washed the motor? if so there could be water in the spark plug holes ( if it has coil on plug holes like most motors now a days)
How old is the battery?
if it's original its junk by now.
If the battery goes low while starting it, the computer has no basics to work from.
Just an idea to work with, a 55K rig should have min. problems like this, so im thinking basics.
Also have you PSI washed the motor? if so there could be water in the spark plug holes ( if it has coil on plug holes like most motors now a days)
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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?
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?
crash2
-Oh no I picked a side-
Typical SB plug setup with coil packs on the valve covers--water, can't see it
