A misfire means a cylinder is not burning fuel properly. Spark plugs and ignition coils cause most misfires, followed by fuel injectors, vacuum leaks and mechanical problems. A diagnosis finds which cylinder and why.
Key takeaways
- Plugs and coils lead.
- Injectors and leaks follow.
- Fix quickly to protect the converter.
Signs
Shaking, hesitation, rough idle, a flashing light and a smell of fuel.
Ignition causes
Worn plugs and failing coils.
Fuel and air causes
Clogged injectors and vacuum leaks.
Mechanical causes
Low compression from valve or ring problems, less common but serious.
Fix
Replace worn parts, repair leaks and retest.
Reading the pattern
A misfire on one cylinder points to that cylinder's plug, coil or injector. Random misfires across several cylinders point to a fuel, air or compression problem common to all of them. The code number tells which. A technician swaps parts between cylinders or measures them to confirm. That narrows the repair to one part instead of replacing the whole set.
Why misfires are worse in heat and under load
High temperatures and heavy loads stress ignition parts, so a marginal coil that works at idle may fail on a hot hill. Bakersfield summers expose weak coils and plugs. If your car runs fine in the morning and misfires in afternoon traffic, tell the shop. That pattern points to parts that fail when hot and helps the technician test under those conditions.
Need help in south Bakersfield?
Questions about check engine light? Read our Check Engine Light page, call (661) 599-9098 or request a time. Peña's Auto Electric, Smog & Repair, 303 Taft Hwy, Suite B, Bakersfield, CA 93307. Mon to Fri 9:30 AM to 5:30 PM, Sat 8 AM to 1 PM.
Frequently asked questions
Why is my engine shaking?
A misfire is a common cause.
Can I drive with a misfire?
Not for long.
Do coils fail often?
As they age, yes.
Does a misfire fail smog?
Yes.