GM Repair Problems? Ask GM Repair Expert Now.
Good afternoon, Disconnect the two pin connector on top of the intake, it should have Blue wires. Ohm each wire to ground on the knock sensor side. They should have resistance between 93K-107K ohms for each wire. If not in specification, remove the intake manifold and check the connections and wiring to the Knock Sensors . If they ohm tested OK, verify the wiring to the Powertrain Control Module is not open or grounded. If OK, tap on the exhaust manifold with an extension while monitoring the ac voltage produced by each sensor. If the sensor does not produce a good voltage compared to the other sensor, re-replace the lower output sensor. Be sure to torque the sensor properly, over-tightening can damage a new sensor. Tighten to 15 foot pounds (20 Nm). If the code is coming up than I am sure it is throwing off the timing like it should causing your running problems. As for the problem with the leak that is what it looks like if the fuel tank got topped off and the excess gas is slowly leaking through the charcoal canister.
If it was oil it would never evaporate. But there should not be any oil in your fuel system. So it is possible that you have a leak on the engine and it sprays back to the canister from the fan and just the angle of the leak.
I would replace the charcoal canister. It does not sound good. This can cause issues with the emissions system making problems with it running as well. It should always be dry. Sometimes they get contaminated and if that happens we replace them. I would say it is a combination of some old gas and the charcoal canister. It would be a good idea to do this soon.
It would not hurt just to ensure you do not have it fail in the near future, they can fail over time from normal use. The vehicle is 16 years old and it could be on the end of its lifespan.
The knock sensor code will only come on if it sees the fault several times. It will for sure retard your timing to protect your engine causing a very poor running condition. You can let it go but this is kind of annoying if it keeps doing it.