1010 W Commonwealth Ave, Fullerton, CA 92833 Tue–Fri 9:00 AM–6:00 PM · Mon & Sat by appointment · Sun closed ASE Certified Master Technician · Family Owned
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Diagnostics & Safety

Engine Misfire When Accelerating: What Could Be Wrong?

Updated October 24, 2026 · Cedillo's Classic & Auto Repair, Fullerton

Quick answer: A misfire under acceleration can involve ignition, fuel delivery, air leaks, engine management or mechanical compression. Diagnostic testing is more reliable than replacing spark plugs or coils by guesswork.
Genuine auto repair shop photo at Cedillo's Classic & Auto Repair in Fullerton

When your vehicle feels, sounds or behaves differently, describing the symptom can be more useful than guessing at a repair. Here’s a practical breakdown from Cedillo’s Classic & Auto Repair in Fullerton.

What a misfire feels like

Drivers may report stumbling, shaking, hesitation or reduced power when pressing the accelerator. Note whether it happens with a cold engine, on hills, under load or at a certain speed.

Multiple systems can create the same symptom

Spark plugs and coils are possibilities on modern engines. Fuel injector problems, air intake leaks or mechanical faults can cause similar behavior. Classic carbureted vehicles may require a different diagnostic approach.

Why fault codes are a starting point

A stored misfire code identifies detected behavior, not necessarily the failed part. A technician can combine fault data with measurements and symptom reproduction to decide what to test next.

Did you know?

A flashing check-engine light during a misfire may indicate risk of catalytic-converter damage on many modern vehicles.

Maintenance and observation tip

Write down whether the check-engine light flashes or stays steady and what the engine is doing at that moment. Avoid hard acceleration if it is running poorly.

Safety first: when not to continue driving

If the check-engine light flashes, the engine severely loses power or the vehicle becomes unsafe, reduce load, stop safely and arrange inspection.

Frequently asked questions

Should I replace the ignition coil first?

Not without identifying the cause. Several systems can produce similar symptoms.

Can a classic car misfire without electronic codes?

Yes. Older ignition and carburetor systems may need mechanical and electrical testing without an OBD code.

Related Cedillo’s service guides

Need an inspection in Fullerton?

Owner Rafael Cedillo is an ASE Certified Master Technician with more than 25 years of experience. Cedillo’s Classic & Auto Repair welcomes classic cars, trucks, SUVs and everyday vehicles at 1010 W Commonwealth Ave, Fullerton, CA 92833. We also serve drivers from Anaheim, Placentia, Brea, Buena Park, La Habra, Yorba Linda and Orange.

We believe in explaining the issue and recommending appropriate next steps. Call (714) 681-0101 or request service online. Tuesday–Friday 9 AM–6 PM; Monday and Saturday by appointment. Online requests are not confirmed appointments.

Requests go to our team for follow-up, not guaranteed booking.