2005 rough idle, codes, P0131 P0171 P0300

[bmklawt]

These are the codes I got when Autozone checked it P0131, P0171, P0300

I have a 2005 Silverado, 5.3L with 27000 miles. A few days ago when is was 20 degrees out I started the truck and it was running slightly rough, thought it might be because its cold then I noticed when I stop at a light it idles rough. Idles rough even when warmed up and is only slightly noticeable when cruising 45-55 MPH.

Have been searching the net and come up with various solutions, check intake manifold for leaks, exhaust leak, vacuum leak, but the one that pops up the most is O2 sensor.

Read this somewhere and it makes the most sense so far.
Replace 02 sensor, drivers side front, the p0171 code means that bank 1 (left bank) is running lean. followed by the p0131 which is related to the bank 1 sensor 1 o2 sensor. and p0300 is an engine misfire.

Wanted to check on the forums first and make sure this is the correct information (replace O2 sensor)

Also read I need to get the PCM? reprogrammed if sensor is replaced. Is this true? I thought it would reset itself if it was good after a few starts.

Your help will be much appreciated.
Bruce

[discnik]

You appear to have a vacuum leak. This will set all the above codes. I do not think you need to replace the O2 sensor it is telling you what the P0171 monitor is telling it. A vacuum leak can cause the misfire code. So it would seem that the PCM is telling you to check all your vacuum areas for a leak.

This would also include the PCV valve, EGR valve, and the EVAP lines. Anything and Anywhere unmonitored air can enter the system.

Hope this helps.

[bmklawt]

Had Autozone clear the codes after they checked them.
Last night I started the truck cold and it ran fine for about a minute, then It would idle rough, again this morning I started it cold and it ran fine for a minute then started idling rough again, The engine light came on, had Autozone check it again and this time I get code P0300 and P0171.

I know very little about electrical but it would seem to me to be the o2 sensor, doesn't the truck ignore the o2 sensor until it is warmed up.

How do I check for vacuum leaks?

Your help is much appreciated.
Bruce

[wafrederick]

Needs intake gaskets and 5.3s are known for for intake gaskets.They suck in air causing the miss.spray carb cleaner near the intake gasket area and if it changes,the intake gaskets.You do not have to remove any coolant,ther are no coolant passages to the intake.

[discnik]

wafrederick has the right of it. Spray carb cleaner or starting fluid around the intake area. If the engine idle changes you have found the leaking area. Or as I stated before any area wheree unmonitored air can enter.

[wafrederick]

The intake gaskets are plastic and do blow out.Most parts stores stock the intake gaskets knowing they are problem

[discnik]

I know that Dorman and Fel-Pro make a metal and rubber gasket set for the 3.1 & 3.4's do they also make the metal & rubber ones for the 5.3 L ? Because the plastic ones really are JUNK !

[wafrederick]

I have not seen a metal and rubber intake gasket for the 5.3 yet.The dealer price is about $107.00 for the intake gaskets and about $75.00 for the aftermarket which are plastic.They clip on the intake held in with the intake manifold bolts.

[j cAT]

driver side is running lean and you have miss fires...this could be PCV valve/hoses or the fuel pressure is incorrect...as well as other items that could cause this condition ...pressure test of the fuel pump is what you need to do before you start ripping the engine apart....

you could also have a dirty injector on the driverside as well..

[wafrederick]

I have seen this happen and it was the intake gaskets on a 2000 with a 5.3,sprayed carb cleaner near the intake gasket area and it changed.Ran like a champ after replacing the intake gaskets.

[bmklawt]

Thanks all for the help,

I visually checked for vacuum leaks and saw nothing obvious, I sprayed around the intake with carb cleaner and heard no change in the way it ran.
I started spraying around all the vacuum hoses and got nothing, so I replaced the o2 sensor and it still had a rough idle so I started man handling all the hoses and wire connections and found one vacuum hose that starts up over the right head and goes to the top front of the intake that was not a good fit.
I put hose clamps on both ends and drove to the dealer to get a new one, the truck runs good now and the idiot light eventually went out.
Repair cost $8.07 what I needlessly spent $72.64

[j cAT]

Originally Posted by bmklawt

Thanks all for the help,

Found one vacuum hose that starts up over the right head and goes to the top front of the intake that was not a good fit.
I put hose clamps on both ends and drove to the dealer to get a new one, the truck runs good now and the idiot light eventually went out.
Repair cost $8.07 what I needlessly spent $72.64

when you say RIGHT is that passenger or driver side...
and what is the hose diameter ? what do you think it is for ?

[bmklawt]

j cAT, passenger side

I looked up the part number for the replacement hose I got and it says it's a PCV hose.

Thanks everyone for your help,
Bruce

[j cAT]

Originally Posted by bmklawt

j cAT, passenger side

I looked up the part number for the replacement hose I got and it says it's a PCV hose.

Thanks everyone for your help,
Bruce

thanks for that info..I believe that hose vents the crankcase ...since it was not securely connected , the engine oil may have added dirt in it....

[kahjdh]

I dont know if anybody else has experienced this but we had alot of 5.3's come into the shop w/ bad intake gaskets and we threw a new set on them. After about 6months they come back with the same problem and when we smoke test them it is the same ports leaking. These plastic intakes are like the 3.8L and warp causing leaks.

If this problem coms back Dorman sells whle intake kits which we replace everytime now to prevent comebacks and pissed off customers. Just my 2 cents.