Check Engine Light Turning On and Off? Why Clackamas Drivers Trust Tim’s Automotive Repair and Sales
Few things make drivers more uneasy than the sudden appearance of the check engine light (CEL). Sometimes it stays lit, other times it vanishes the next time you start your car. Many drivers assume, “If it went away, the problem must have fixed itself.” Unfortunately, that’s almost never the case.
At Tim’s Automotive Repair and Sales in Clackamas, OR, we’ve seen this countless times. A CEL that flickers on and off usually means your car is experiencing an intermittent fault — a problem that happens under certain conditions but hasn’t yet failed completely. Ignoring it gives small issues time to grow into expensive repairs and surprise breakdowns.
This guide explains:
Why your check engine light sometimes comes and goes
The most common culprits behind intermittent CELs
Why waiting is a gamble with your vehicle’s health
How Tim’s Automotive accurately diagnoses the real cause
Why drivers in Clackamas and the greater Portland area trust us with their vehicles
Why the Check Engine Light Comes and Goes
Modern vehicles are equipped with an OBD-II system (On-Board Diagnostics) that constantly monitors engine performance, emissions, and sensor feedback. When something falls out of range, the CEL is triggered.
But here’s the key:
Even if the light turns off, the error code is still stored in your vehicle’s computer.
A disappearing light doesn’t mean the issue went away — it means it’s intermittent.
Intermittent issues almost always get worse with time.
Think of it like a smoke detector that chirps randomly. Just because it’s quiet now doesn’t mean the problem disappeared.
Common Causes of an Intermittent Check Engine Light
At Tim’s Automotive Repair and Sales, the most frequent issues we diagnose include:
1. Loose or Damaged Gas Cap
A poorly sealed or cracked gas cap allows fuel vapors to escape, tripping the EVAP system. Tightening it may help, but if the cap is worn, the CEL will return.
2. Oxygen (O2) Sensor Problems
O2 sensors monitor exhaust gases to fine-tune fuel delivery. A sensor starting to fail may only send bad readings occasionally, making the CEL appear and disappear. Left alone, this can reduce fuel efficiency and damage the catalytic converter.
3. Spark Plug or Ignition Coil Misfires
Misfires often happen only under certain conditions, like heavy acceleration or cold starts. Once the misfire stops, the CEL may turn off — but repeated misfires damage plugs, coils, and converters over time.
4. Catalytic Converter Efficiency Issues
A failing converter may still function part of the time but trigger occasional warnings. By the time the CEL stays on permanently, replacement is often necessary.
5. Vacuum Leaks or Electrical Connection Faults
Cracked hoses, worn gaskets, or loose wiring often cause “ghost” faults that come and go. Proper diagnostics are the only way to confirm these issues.
Why Ignoring It Is Risky
It’s tempting to keep driving when the CEL disappears, but here’s why waiting is a bad idea:
Fuel Economy Loss – A failing sensor or ignition problem wastes fuel, even when the car feels fine.
Hidden Damage – Misfires and faulty readings quietly damage pistons, spark plugs, and catalytic converters.
More Expensive Repairs Later – A $100 fix today can snowball into a major repair bill tomorrow.
Unexpected Breakdowns – Intermittent problems often become permanent at the worst possible moment — like commuting into Portland or heading over Mt. Hood.
What To Do If Your CEL Turns On and Off
Here’s a simple plan for Clackamas drivers:
Check the Gas Cap – Make sure it’s tightened until it clicks. If the CEL returns, it may need replacement.
Note Any Symptoms – Rough idle, hesitation, or poor MPG? Write them down.
Don’t Assume It’s Fixed – Even if the CEL disappears, the code remains stored.
Schedule a Diagnostic at Tim’s Automotive – Our ASE-certified team will scan your system, review live sensor data, and confirm the true cause.
The Tim’s Automotive Difference
When you bring your vehicle to Tim’s Automotive Repair and Sales, 15688 SE 135th Ave, Clackamas, OR 97015, you’re not just getting a quick scan — you’re getting a complete diagnostic process built on honesty and precision.
Advanced Diagnostics – OBD-II scans, live data testing, and hands-on inspections.
Thorough Explanations – We explain what’s happening in plain terms and give you clear options.
Trusted Repairs – We fix it right the first time, with your long-term reliability in mind.
Complete Auto Care – From diagnostics and maintenance to tires, brakes, and suspension, we handle it all.
Customer-First Philosophy – Our focus is on protecting your safety, your wallet, and your trust.
Serving Clackamas and the Greater Portland Area
We’re proud to be the trusted repair shop not just for Clackamas, but also for:
Happy Valley
Milwaukie
Oregon City
Damascus
Southeast Portland
Wherever you’re driving in the region, you can count on Tim’s Automotive for accurate diagnostics and dependable repairs.
The Bottom Line
A check engine light that turns on and off isn’t a fluke — it’s a warning that your car needs attention.
At Tim’s Automotive Repair and Sales, we’ve built our reputation in Clackamas on trust, integrity, and getting the job done right.
Call us today at (503) 656-0600 or schedule service online attims-automotive.com. Don’t wait until a simple issue becomes a costly repair.
You can watch the video
https://youtu.be/sciAnEdwFK4