Hey, everybody.
I have a Corvette C6 2012 Base (LS3). After being parked for a long time after a repair, the following problem happened to me:
At one moment, after fueling the car more than half and driving around a bit, I saw that I have a gas leak from the tank.

I pulled out a simple scanner I recently bought and saw the following readings:
1. at idle on a warmed up car, the EVAP_VP reading is -32.7 inH20, with the norm being about -10 inH20.
2. if to increase rpm (about 2000), the sensor sharply changes the value to +32,7 inH20 with maximum values about +2...+4 inH20.
3. O2 sensor readings at idle: they either show all about 0,8V or about 0,05-0,1V (if you give some revs, these readings jump from one boundary to another.
4. O2 sensor readings at RPM (about 1500-2500): upstream O2 starts running on a sine wave - from 0.1 V to 0.8 V.
5. Fuel correction readings, also in the 10% range, although it does go beyond 5%.

I checked Purge Valve, it works correctly: on cold engine - closed, on warm engine - pulsing (open - close).
I also have error P0300 and nothing else. The car runs pretty good and smooth, especially at revs. I have checked plugs, wires, etc. - everything is normal. Could a tank leak problem be causing all these problems?

I've also heard that if you don't change the Camshaft Gear (Timing Gear) and the bolt that fixes it during an engine overhaul, the P0300 error can come out. Is this true?

 

As for the p0300, there's multiple causes for random misfires. Vacuum leaks, ignition issues, fuel pressure issues, evap issues .... And yes, a cam gear with too much wear is also a possibility. As a rule on a rebuild, or simply replacing the timing chain, I always replace the cam and crank gear.... And run a relearn for the position sensors.

If you have a visible gas leak under the tank, better get that thing in the air and see exactly what's leaking. No doubt that leak is the source of the EVAP codes. Don't forget to check the top of the tank where the fuel pump mounts. Pretty common for the top to rust ending up with a leak. Before diving in on the camshaft gear, I would fix the fuel leak first, clear the codes, and take it for a drive...

 

Can anyone help? 🙏

Adding: write message in one time) Thank you rdezs for reply.

 

Thank you. I think the chain and cam gear could be the cause just due to wear too. But the mechanic who did the repair changed the chain, but not the cam gear, crank gear and e.t.c.... I'll have to remove the cover and replace everything. I have no EVAP codes and probably won't until I fix the p0300 problem. If I understand correctly from internet resources, until the engine problem is resolved, all other systems like the EVAP, will not work or won't work correctly.

 

For additional information: all cylinders have misfire. I think it could be due to fuel pump/leaks or with cam/crank gear. What's your thoughts?

 

That could easily be timing chain off a tooth, or the gears worn. Get a complete timing gear and chain set, with tensioner when you replace. (I wouldn't reuse the chain you have on there now)

Make sure you have a genuine GM or ACDelco camshaft position sensor and crankshaft position sensor. And do the relearn. Check the harness plugs closely, along with the wires a couple inches up from the sensor plugs. And as usual, verify your ground connections are good.