Last week my fiancé and I tore apart my 02 Chev Silverado 5.3L Vortec V8 to replace the knock sensors. Finally got it up and running Friday night - it ran beautifully that night, no codes or anything. Saturday morning I fire her up, let her warm up for a few, and pull away. On comes the CEL and at low speed/rpm I have some grinding/vibration coming through the pedal and an icky groaning noise. It seems to occur the most under 30 mph and at low rpms. If I punch the accelerator it stops. The engine is running just fine whether I am accelerating, braking, or idle. I have thrown another code and will have the boys at the local O'Reilly pull the code for me - my guess for the code though is EVAP because when I pulled the knock code I had 3 EVAPs as well and this was not happening. Any suggestions? I am still driving her because as I said, the engine is running fine, it's just this nerve wracking new development. Barring an obvious code what could this be?

Thanks in advance!

 

Update! Pulled codes this afternoon after work. I have 2 EVAPs (improvement from two weeks ago) and a Random Misfire Lame. The misfire wouldn't be the cause of the noise, would it?

 

This type of a noise is usually produced by a faulty power steering pump or transmission. Mostly, it could be like a noise on the transmission itself. It would be nice if you flush the transmission and cause it is so new.

 

I checked tranny fluid day yesterday after work (before I pulled codes - I felt like the shift was a little retarded), color was good, smell was fine, no obvious particles. What about the grinding feeling coming through the pedal? That wouldn't be relative to the steering pump would it? To me it's strange that it would be perfectly fine before we pulled her apart to do the knock sensors - but that would be my luck anyway.

On a side note, this morning I was almost to work and she has started chugging when I let off the brake but before I press the accelerator...

 

Amber it may not be your engine at all. I had a problem like this on my 02' z71. The problem has happened 2x in the 7 years i have had the truck. First was a steady grinding noise that was audible outside and the other made no noise outside but could be felt through the wheel and peddles. Turned out the problem was the drivers side wheel hub. It is easy enough to check: simply remove the wheel and brakes (caliper & rotor), then look and feel for any play or grinding in the hub. The hubs are a sealed unit held on by 3 bolts and should have 0 slop in any direction (up/down, front/back, driver/passenger) and should spin smoothly and easily. May need a 35mm socket to back off the hubs locking nut. shouldn't take more than 30-45 min to check & replace. be sure though to torque the hub nut back down when done. 135 ftlbs is the spec on the nut. good luck and hope this helps.

If it is the hub replacement part is $119 (1 yr warranty) or $149 (3 yr warranty) from O'Riley auto

(1st time for me felt only grinding till the hub separated and began throwing bearings. The 2nd time the bearings were locking up inside the hub and it felt almost as if the trans was slipping or the engine was stumbeling)