B0004 the main thing to check is to verify the operation of the VCT solenoid. You're looking for a sticking or stuck VCt solenoid valve caused by contamination. Refer to vehicle specific repair manual to perform component tests for the VCT unit.
The scent may B0004 signal oil or coolant leaking from their normally closed-loop systems, or it may indicate dangerous exhaust gases invading your car's interior. Car and truck exhaust contains toxic gases such, so if the inside of your car as if you were standing behind your car, get out and get it fixed. Fight the urge to take a little nap first. So sleepy. That's the carbon monoxide talking, friends. At least open a window on your way to the shop.
When you fill your car with gas, the vapors in the tank get forced into a canister filled with activated charcoal. Also, on a hot day as the gas heats up and vaporizes, those same vapors push into the canister where they're stored. But the charcoal can only hold so much vapor. At some point it has to be emptied. The emptying process is called canister purge.
Indicator and headlight bulbs need regular maintenance for them to keep functioning properly. Also the car paint ought to be in good condition because that reduces the chances of rust taking over the body of your car. This is one of those car maintenance problems, which are easy to handle, given the variety and quality of products available in the market today.