2004 Tahoe - Vacuum Leak or MAF?

[scronch]

2004 Tahoe with the Z flex fuel engine

 

I was changing the serpentine belt and after removing the top plastic cover, the intake horn (from the MAF to the intake) and the radiator fan upper shroud, I found the idler pulley tensioning spring was stuck in position. I got it loose but I did pull the driver handle more than I wanted into the two hoses (one large, one small) coming from the pax side radiator. Other than that, nothing unusual.

 

Reassemble, test drive and the engine is chugging at idle in forward or reverse. In neutral engine is hunting around 600 to 700 rpm and sounds rough. I did not disconnect the battery at all so I don't think this is a retraining issue. Never had this problem before doing the serpentine belt.

 

Threw codes P0171 and P0174 so both banks are too lean. I figured I somehow caused a vacuum leak. Pulled the top cover and intake horn again and inspected all I could see--nothing obvious. Ran the engine and sprayed carb cleaner around the intake manifold gasket, the injectors, PCV valve, top of the engine, etc... no change in rpm. I did this with engine cold and the idle wasn't too bad. Test drove it and as engine warmed up the chugging at idle came back.

 

So... the symptom is hunting idle and chugging in gear at idle when engine has warmed. with codes P0171 and P0174.

 

I don't think I dirtied or damaged the MAF sensor, but maybe I did.

 

Ideas on what to try next?

 

Thanks.

 

[riverbanks]

Stuff happens,I did a intake gasket a while back,put all parts on workbench, including MAF,it never worked right again, just cause I moved it

[davester]

You could also have a wiring or connector issue.