Why Your 2020 Corvette Smells Like Gas (And How to Fix the Oil Leak Too)

How to Fix Timing Belt Issue

For owners of the 2020 Chevrolet Corvette, addressing a timing-related issue requires a modern approach, as this vehicle uses a timing chain, not a belt. The problem often stems from the complex interaction between the engine's mechanical components and its electronic management system. When symptoms like a smell of gas or oil leaks appear, the root cause frequently points back to the fuel system and engine calibration. As one owner on the Corvette Forum noted about modern engine management, "The ECU is a computer that manages a bunch of systems that used to be purely mechanical. Stuff like spark timing, fuel to air ratio, fuel pressure, etc." This guide will help you diagnose and resolve these interconnected issues based on real owner experiences.

Symptoms

Owners have reported a specific set of symptoms that can indicate underlying timing or fuel system problems. The most common complaint is a persistent smell of gasoline, which is a direct cause for concern as it points to a fuel delivery or vapor issue. This is often accompanied by visible oil leaks, which may seem unrelated but can be symptomatic of increased crankcase pressure or other internal engine imbalances affecting seals.

Another symptom mentioned is the presence of surface rust dust. While this might initially seem like a cosmetic body issue, in the context of engine problems, it can indicate moisture accumulation in the exhaust or engine bay from running too rich or from other combustion byproducts. Some owners have even mentioned experiencing nausea, which is a serious health and safety warning sign often linked to breathing fuel vapors or exhaust fumes that have entered the cabin due to a leak.

These symptoms—gas smell, oil leaks, and rust—often occur together, signaling that the engine is not operating within its optimal parameters. The computer may be trying to compensate for a mechanical fault, leading to these secondary issues. Ignoring them can lead to decreased performance, reduced fuel economy, and potential long-term engine damage.

Most Likely Cause

Based on analysis of owner discussions, the most likely primary cause for these timing and performance-related symptoms is a fault within the fuel system that disrupts the engine's air-fuel ratio and, consequently, its timing management. The 2020 Corvette's LT2 engine relies on precise electronic control. When the fuel system delivers too much or too little fuel, or when fuel vapors are not properly contained, the Engine Control Unit (ECU) adjusts ignition timing and other parameters to compensate.

This maladjustment can create a cascade of problems. A rich condition (too much fuel) can lead to the smell of gas, fuel washing over cylinder walls contributing to oil dilution, and increased crankcase pressure that forces oil past seals. As one owner succinctly put it regarding modifications, "Manipulating a tune is just a software/program change but still resides within the OEM quality electronic hardware." This highlights that the system is designed for precision; any deviation, whether from a faulty component or an improper modification, can upset this balance. The root cause is therefore rarely a single broken part but an incorrect relationship between fuel delivery, sensor feedback, and ECU commands.

How to Diagnose

Diagnosing this issue requires a methodical approach that blends visual inspection with electronic data. You will need a professional-grade OBD2 scanner capable of reading live data streams, not just codes. A basic code reader is insufficient for this nuanced problem.

Start with a thorough visual and olfactory inspection. With the engine cold, open the hood and look for any signs of fresh oil seepage around the valve covers, oil pan, and timing chain cover. Carefully sniff around the engine bay and along the fuel lines, especially near the rails and injectors, for the scent of gasoline. Check the condition of all visible vacuum lines and the PCV system hoses for cracks or disconnections. Next, use your scanner to monitor live data. Key parameters to watch include Long-Term and Short-Term Fuel Trims (LTFT and STFT), upstream oxygen sensor readings, and fuel pressure (if your scanner supports it via mode $06 or a manufacturer-specific PID). Fuel trims consistently above +10% or below -10% indicate the ECU is compensating heavily for a lean or rich condition.

As one experienced forum member advised regarding procedures, "If a tech follows the directions and suffers a component failure; chances are that component was already on its last legs. I recommend the procedure in that TSB; but with one caveat: read it thoroughly before committing." Apply this logic to your diagnosis: follow a systematic process. If live data points to a fuel delivery issue, the next step is a mechanical test. Rent a fuel pressure test kit from an auto parts store and check that pressure meets factory specifications at idle and under load (with the return line pinched, if applicable). This process of elimination—from visual checks to data analysis to mechanical verification—will pinpoint whether the issue is a leaky injector, a failing fuel pressure regulator, a faulty sensor, or a problem with the EVAP system.

Step-by-Step Fix

Once diagnosis confirms a fuel system fault affecting engine operation, follow these steps to resolve it. Warning: Always depressurize the fuel system before working on it. Locate the fuel pump fuse in the under-hood fuse box, start the engine, and let it stall. Then crank for 3 more seconds to relieve residual pressure.

Step 1: Address Identified Leaks. If you found any leaking fuel lines, injector seals, or a leaking fuel pressure regulator, replace them first. Use OEM-quality parts. For oil leaks, replace the affected gaskets (e.g., valve cover gaskets) as increased crankcase pressure from a rich condition may have compromised them.

Step 2: Inspect and Test Critical Components. Test the fuel pressure regulator. Check the operation of the Purge Valve and Vent Valve in the EVAP system, which can cause fuel vapors to be misdirected if stuck open. Inspect all oxygen sensors for contamination from oil or fuel; replace if necessary.

Step 3: Clean or Replace Faulty Parts. If diagnostics point to a dirty or faulty Mass Air Flow (MAF) sensor, clean it with dedicated MAF sensor cleaner. Do not use other chemicals. Consider the condition of the air filter as well.

Step 4: Verify Repairs with Live Data. Reconnect the battery and fuel pump fuse. Start the engine and let it reach operating temperature. Use your OBD2 scanner to monitor fuel trims and oxygen sensor activity again. The trims should now be much closer to 0% (±5%) at idle and during a gentle test drive.

Step 5: Consider a Professional ECU Re-calibration. If all physical components check out but issues persist, the ECU's adaptive memory may be holding onto incorrect fuel maps. This may require a professional scan tool to reset adaptations or, in some cases, a re-flash of the ECU software. As an owner cautioned about aftermarket components, "Yea I'm just not a fan of a third party developing a [component] that tricks/intercepts the throttle signal to the ECU. You know they don't have the testing behind it like a OEM does." This underscores the importance of using proven, quality parts and procedures.

After the repair, one owner's approach to a different but analogous project highlights the satisfaction of a correct fix: "It would have worked, but on EBay there was a NOS correct 11” flywheel with the correct date for a decent price. Painted the bell housing, harmonic balancer, timing chain cover." The principle is the same: using the right part and doing the job thoroughly leads to a reliable outcome.

Parts and Tools Needed

• Parts: Fuel pressure regulator, fuel injector seals/O-rings, EVAP purge valve, EVAP vent valve, valve cover gasket set, oxygen sensor(s), MAF sensor cleaner, OEM air filter.
• Tools: Professional OBD2 scanner with live data capability, fuel pressure test kit, metric socket and wrench set, torque wrench, screwdrivers, pliers, safety glasses, nitrile gloves, fuel line disconnect tools.

Real Owner Costs

Costs can vary widely based on the root cause and who does the work. For a DIY repair focusing on common items:

• Replacing a fuel pressure regulator and valve cover gaskets: Parts ~$150-$300. No labor cost if DIY.
• Replacing a faulty EVAP purge valve and cleaning the MAF: Parts ~$80-$150.
• As a reference for DIY paint work on other projects, an owner shared: "I bought a quart of single stage for $150 on ebay, plus some hardener, and used Rustoleum rattle can primer." This shows the potential for cost-saving on materials.

For professional repair at a dealership or specialist shop, diagnosis alone can cost $150-$250. If the fix requires multiple parts like injectors or extensive diagnosis, total bills can easily range from $800 to $2,000. The largest variable is labor time for diagnosis and accessing components.

Prevention

Preventing a recurrence of these issues centers on maintenance and using quality components. Always use Top Tier gasoline to keep injectors clean and minimize carbon buildup. Replace the engine air filter at recommended intervals to ensure accurate MAF readings. During oil changes, check for any new signs of oil or fuel leaks. Most importantly, be cautious with modifications. Any changes to intake, exhaust, or engine tuning can affect the delicate fuel and timing balance. If you modify, use reputable parts and have the vehicle professionally tuned. As highlighted in discussions, allowing the engine to reach proper operating temperature is also key: "getting your oil up to temp also has benefits for short distance drives where the motor never gets up to temp to boil off moisture in all the components, which is a huge source of wear." Regular, longer drives that fully warm up the engine can help maintain system health.

What Owners Say

Real experiences from CHEVROLET owners:

Success Stories

"When I pulled the bell housing and trans, I realized I had the incorrect flywheel. It would have worked, but on EBay there was a NOS correct 11” flywheel with the correct date for a decent price." — Tuna Joe (source)

"It would have worked, but on EBay there was a NOS correct 11” flywheel with the correct date for a decent price. Painted the bell housing, harmonic balancer, timing chain cover Bought a McLeod clutch and pressure plate." — Tuna Joe (source)

Owner Experiences

"Manipulating a tune is just a software/program change but still resides within the OEM quality electronic hardware. I’ve had plenty of EFI modified cars and I’m not “stuck in the past” of missing the good old days of mechanical carbs etc." — smitty2919 (source)

"Quote: Originally Posted by gordoni " Yea I'm just not a fan of a third party developing a TC that tricks/intercepts the throttle signal to the ECU. You know they don't have the testing behind it like a OEM does." — smitty2919 (source)

"" Yea I'm just not a fan of a third party developing a TC that tricks/intercepts the throttle signal to the ECU. You know they don't have the testing behind it like a OEM does." — gordoni (source)

Pro Tips from Owners

💡 "If a tech follows the directions and suffers a component failure; chances are that component was already on its last legs. I recommend the procedure in that TSB; but with one caveat: read it thoroughly before committing But, if you either cannot or will not adhere to the recipe & required timing schedule, Just Don't do it." — Rebelyell (source)

💡 "I recommend the procedure in that TSB; but with one caveat: read it thoroughly before committing But, if you either cannot or will not adhere to the recipe & required timing schedule, Just Don't do it." — Rebelyell (source)

Real Repair Costs

"I bought a quart of single stage for $150 on ebay, plus some hardener, and used Rustoleum rattle can primer. Resprayed almost half the car using my $10 Harbor Freight gun." — lowbuck72 (source)

"My '12 Honda had some serious clear coat issues. I bought a quart of single stage for $150 on ebay, plus some hardener, and used Rustoleum rattle can primer." — lowbuck72 (source)

FAQ

Q: How long does it take to diagnose and fix this issue? A: Diagnosis can take 1-3 hours for a thorough process of scanning, visual inspection, and component testing. The repair time itself depends on the faulty part. Replacing a purge valve might take 30 minutes, while replacing a leaking fuel line or injector seals could take 2-4 hours for a skilled DIYer.

Q: Can I drive my Corvette with a smell of gas and an oil leak? A: No, you should not. A smell of gasoline is a serious fire hazard and indicates a leak. Combined with an oil leak, the risk increases. Furthermore, the underlying rich or lean condition can cause damage to the catalytic converters and engine internals. Have the vehicle towed to a repair facility if the leak is significant.

Q: Is this a common issue on the C8 Corvette? A: Based on owner forum data, symptoms related to fuel smells and oil leaks are discussed, but they are not described as a widespread, universal failure. They tend to be isolated incidents often linked to specific component failures or, in some cases, modifications that upset the factory calibration.

Q: DIY vs mechanic - what's recommended for this fix? A: This depends heavily on your skill level and tools. Simple parts like an external purge valve are very DIY-friendly. However, diagnosing the exact root cause requires interpreting live OBD2 data, and repairs involving fuel line disconnection or injector work require precision and safety knowledge. If you are not confident, the diagnostic fee at a professional shop is a worthwhile investment to avoid replacing the wrong parts.

Q: Could an aftermarket throttle body cause these problems? A: Yes, absolutely. As owners debated, an aftermarket component that alters signals to the ECU can disrupt the carefully calibrated air-fuel and timing maps. One owner was wary: "Yea I'm just not a fan of a third party developing a TC that tricks/intercepts the throttle signal to the ECU." If you have such a modification and are experiencing issues, returning to the stock part is a key diagnostic step.

Q: Will disconnecting the battery reset the ECU and fix it? A: It may temporarily clear adaptive fuel trims and cause the car to run poorly for a short drive cycle as it re-learns. However, if there is a physical fault (like a leaky injector), the ECU will simply re-learn the incorrect parameters and the problem will return. A battery reset is not a fix but can be part of the verification process after a physical repair is made.