2002 Chevy Silverado 1500 16,000 miles 5.3 eratic idle/stumble&miss

cw41

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#1
I have a 2002 chevy 1500 with the 5.3 when cold weather below about 32deg, when starting cold in the morning especially, the idle will be eratic and the engine stumbles like it's missing on a cylinder. The engine will usually die and hard to start back up. When it warms up slightly to about the first mark on the temp gauge, the service light goes off and the engine runs fine. No code is stored on several checks with code reader. During warm weather I have no issues at all! I've put a new IAC on with no results still have the same problem. Would anyone happen to know what might be going on here? Thanks for any help.
 

kev2

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#2
Can code reader check for history or pending?
Try reading before the eng gets to first mark while light still on
first thought with cold weather issues is fuel pressure.

Might want to ck and if you can change fuel filter.
 

cw41

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#3
Thanks Kevin I've change the fuel and air filters, cleaned the throttle body and still have the issue.
 

kev2

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#4
Always easy thngs first- you did fuel filter and air filter - you did not use a problematic K&N did you?
next would suggest look at fuel pressure.
If you have a scanner might want to look at ECT also.
 

cw41

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#5
thanks again Kevin and no I didn't use a K&N, just a new Wix gold. I also replaced spark plugs with new AC Iridium ones. I don't have a pressure gauge for fuel injection so I might have to go to the shop for that. I'm also not familiar with the ECT? Can you explain? Thanks
 

kev2

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#6
if you want to do some work yourself, DIY- a fuel pressure gauge is a must...not to expensive, might want to ask Santa. AND they are sometimes available as loaner tools at the parts house.

ECT= Engine Coolant Temperature - ECM will use to richen the mixture when cold out, the 'choke' of today
 

cw41

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#7
Thanks for the info. have you had any issues with intake gaskets causing this problem. Yes, a pressure gauge is my next tool on my list. thanks
 

kev2

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#8
unmetered air (leak) entering engine would likely cause other issues- fuel trim, eng vacuum, and the PCM should see these BUT with a scan tool you could look at these if no codes. WHY do you mention gaskets...

easier said than done, spraying carb or brake clean at the suspected leaking area, you would hear a RPM change if you spray a leaking (vacuum) gasket ...
 

billr

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#9
If you only have a code reader then another "must have" is a scan-tool that will show live data. You can use that to see if the cold engine temp the PCM is seeing is consistent with the ambient temp, a quick check of the ECT. And, of course, a scan-tool will show much more useful info.
 

cw41

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#10
I wished I had a scan tool, another must have to diagnose these issues. I mentioned the intake gasket as I was searching and found two other people had similar issues when cold that the intake gasket was the problem. I don't think this is the problem but I just don't know?? It looks like another trip to the GM shop is next. thanks again
 

billr

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#11
Pull the electric connector off of the ECT, look for moisture or corrosion in there. Measure resistance across the two ECT pins, should be about 4400 ohms at 60 degrees F.