A misfire is a cylinder that fails to ignite the fuel-air mixture properly. Aside from the rough running and shaking, a misfire that is not corrected can damage the catalytic converter — which is one of the most expensive parts on the vehicle.

Common symptoms

"The engine is shaking or vibrating"
"The car idles roughly or stalls at idle"
"I feel hesitation when I accelerate"
"The check engine light is flashing"

What we check

01 Misfire counters per cylinder, fuel trims and ignition timing data
02 Ignition coils — function and resistance, swap-test where appropriate
03 Spark plugs — condition, gap and heat range
04 Fuel injector operation and balance
05 Vacuum leaks, intake gaskets, PCV system
06 Compression test when a mechanical issue is suspected

A flashing check engine light specifically signals an active misfire and is more urgent than a steady light — driving long distances with a flashing CEL can destroy the catalytic converter.

The cause of a misfire varies widely: ignition (coils, plugs), fuel (injectors, pressure, leaks), or mechanical (compression, valve-train). The fix depends on the actual cause, which we identify before any parts are ordered.

A note on shop equipment

Some repairs cannot be completed safely at a mobile location. After the diagnostic, we will tell you whether the work can be done on-site or whether shop equipment is required, before any repair begins.

Engine Misfire & Rough Idle Repair

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