PriceProtect™
DriveShield™
GarageGuard™
Services
Insurance
Car Insurance
Compare Car Insurance with Jerry
Jerry’s Expert Advice
Car Insurance Estimates
Home & Renters Insurance
Renters Insurance
Repairs
Car Repair Estimates
Repair Estimates for Popular Services
Advice
Read Car Content
Browse Jerry Car Advice
Check Out Expert Car QnA
Learn About How We Create Content
Jerry Data & Research
What is a spark plug defouler and what does it do?
I’ve read on some forums that you can use a defouler instead of getting new spark plugs. What is a spark plug defouler and what does it do?
Bonnie Stinson · Updated on
Reviewed by Shannon Martin, Licensed Insurance Agent.
Glad you asked! A defouler is an aftermarket component that can trick the O2 sensor by creating flow for fuel vapors, even if the spark plugs are dirty.
The defouler screws onto the spark plugs and acts as a sleeve, creating room for vapors and
preventing spark plug damage. A clogged spark plug will prevent healthy combustion and may cause problems when
passing emissions testing
.Some people choose to add the spark plug defouler to an O2 sensor, tricking it into appearing perfectly functional—and thus removing the P0420 code, which is a low catalyst efficiency system warning. To be clear, this is rigging the vehicle and it’s not legal.
A better solution is to replace your old spark plugs.
Hope this helps!
If you’re looking for ways to cut costs as a car owner, you might start by looking for a cheaper
car insurance
policy. Most people are needlessly overpaying for coverage—the free Jerry
app can help you find out. Best of all, you’re just a few taps away from swapping to a cheaper policy.View full answer
- Gregory R.
WHY YOU CAN TRUST JERRY
Jerry partners with more than 50 insurance companies, but our content is independently researched, written, and fact-checked by our team of editors and agents. We aren’t paid for reviews or other content.
Join 4M+ members in lowering their car insurance
You Might Also Be Interested
Read Advice From Car Experts At Jerry
What Others Are Asking
Browse More Content
Insurance in Your State
Easiest way to compare and buy car insurance
No long forms
No spam or unwanted phone calls
Quotes from top insurance companies