I have a 2002 GMC Yukon with the 5.3 liter engine and 114k miles. When it is below 38 degrees, it idles really rough and eratic jumping from what seems to be the choke on then off and then to below 500 rpms and almost dying. When it is above 40 degrees, it idles perfect. I took it to a local auto parts store for the codes to be read and it said bank 1 and 2 lean and bank 2 O2 sensor. I replaced the sensor and it helped somewhat due to the fact that once it is warmed up, it idles fine. To date, this is what I have done....
new fuel filter, new plugs and wires, new battery, fuel injectors cleaned with the machine, a couple of bottles of sea foam, non-ethonal gas in the tank, throttle body cleaned-wasn't dirty to begin with. I had the fuel pump checked by a local shop and they said the pressure was good according to their machine.
Is there an idle sensor of some sort? I haven't checked the codes again since having the check engine light come back on after the reset.
Based on your lean codes I think your intake gaskets are leaking vacuum. That has been a common problem for those engines. I would also clean the MAF sensor.
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Based on your lean codes I think your intake gaskets are leaking vacuum. That has been a common problem for those engines. I would also clean the MAF sensor.
Is there a "correct" way to clean the MAF sensor? Should I remove it and spray carb cleaner through the honey comb looking screen?
Compressed air?
Well, the MAF looked clean as the day it left the factory, but I went ahead and hit it with a little compressed air being careful not to damage the little hair looking wire things. Intake Manifold gaskets huh?
Maf is cleaned with a can of brake cleaner. Although a dirty maf will typically cause it to run rich. It could be something with the IAT sensor, I don't think a vacuum leak is temp. sensitive. I'll keep thinking about it....
Well, the MAF looked clean as the day it left the factory, but I went ahead and hit it with a little compressed air being careful not to damage the little hair looking wire things. Intake Manifold gaskets huh?
Actually they make a MAF Cleaner called,,,,you guessed it Mass Air Flow Cleaner. It's made by CRC ,, it's in a gray spray can and you can find it at Advanced Auto Parts. Maybe else where too.
You need to find someone with a scanner that can look at all your engine sensors after your car has set over night. That way they can look at the temp sensors and compare them to the outside air temp. That's always the best place to start.
To find your vacuum leaks,,, if you have them the best thing to do is find someone with a "smoke" machine. Blow the smoke into your power brake booster vacuum line into your manifold without the engine running and look for the smoke to come out of your vacuum leaks.
You need to find someone with a scanner that can look at all your engine sensors after your car has set over night. That way they can look at the temp sensors and compare them to the outside air temp. That's always the best place to start.
That is what I am thinking......probably end up taking it to the Stealership, as much as I hate to - $$$$$
Dont take it to the dealership. Buy a can of carb/choke cleaner. Brake parts cleaner works too. Start it up, spray it around the intake/head mating areas and listen for the rpm drop/rise. My money is on the intake gaskets. They are super easy to swap too.
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Help with '02 GMC Yukon rough cold idle.
