Envoy 2002 unsteady RPM and engine while stoping

Should idle between 500-600. Clean your throttle body with the battery disconnected to help with the fluctuation. The roaring very well could be your fan clutch. Fan clutches are a known problem with our platform. If engaged, will sound like an airplane.

Starting point is always cylinder 1, on straight engines at the front, on V engines front left. The gear wheel or crank sensor will register at TDC or just before. TDC can be found with a pencil inserted in the spark plug hole of cylinder 1
So for a 4 cylinder engine it's 1,3,4,2
6 cylinder straight, 1,3,5,6,4,2,
Cant remember the v engines but it's always left right etc.and from end to centre.

Could need an engine rebuild you cannot drive without oil and not do damage to the bearings.

have the engine code read that will give you a new starting spot. without just throwing money at it.

I don't see any need to go into a long story here

You have at least two problems that may not be
all that big a deal

I would flat bed it to a dealer or local repair shop

if its at the top end its pistion slap
if its at the bottem end(of your engine) its a crank shaft bearing.

with out going into extream detail,

a ting sound at the top is a pistion slap.... replace all your pistions posibly over hual the engine.

a dubble knock that gose with rpm but sounds 2 knocks very every fireing of the pistion is a crank bearing..... replace your crank shaft bearings.... all of them b/c metal gose threw an engine extreamly fast and will destroy other beraings. this knock on start up will turn into a knock all the time, then a very louad knock that will end your engines life.

unfortunetly the answer is engine rebuild and fast.

This could be a bad key. Expensive but if necassary to replace to check on the symptom of the car since no codes are being thrown. I would also say check your Idle Air Control valve and your EGR valve to make sure they are working proplery

fan cluch check the fan cluch

you may need a instrument cluster

If your 2002 gmc envoy or sierra will not even turn over with a kown good battery try starting it in nuetral then go back to park and try starting again. There is a park nuetral safety switch that can malfunction. Turn the key on then shift into nuetral, then turn fully to start.