Skip the auto shop - Our mechanics make house calls

Q: I changed spark plugs and wires & cleaned throttle body, car idles rough and gas mileage is changed does not backfire or anything

asked by on

I cleaned the throttle body with bottle body spray and changed the spark plugs and wires. vehicle starts fine drives okay but I noticed a hesitation during idle like a bump at periodic intervals, also seems to be burning a little more gas. Spark plugs were pre-set from the company (set 0.040) I did not check them prior to installing them in vehicle.

My car has 132000 miles.
My car has an automatic transmission.

A: A few different components could be causing...

A few different components could be causing your issue. Your symptoms sound at first like a spark issue. If a plug was tightened down too hard, the gap can become smaller than intended. This would decrease the power of the spark and lead to a misfire.

Due to the fact these were just changed, I would inspect them and verify the repair is holding. If the vehicle is having a strong enough misfire, it will likely set a diagnostic code. You should attempt to have your car scanned, and see if any sensors are showing a problem. Some codes will not trigger the Check Engine Light, but will still help narrow down the cylinder that is having an issue.

If you need help with getting this fixed, consider YourMechanic, as one of our mobile technicians can come to your home or office to diagnose your misfire condition and help you fix it accordingly.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: Four-wheel drive service message appearing

Hi there. The system uses the instrument cluster module to alert issues with the 4WD system on you vehicle. The issues can be diagnosed by scanning your computer system to identify a possible problem. Your system may have a poor...

Q: Car not starting, though fuses and plugs okay.

Does the engine crank? There are many reason why a car will crank but not start. Your engine will not start unless it has fuel, air, spark, and compression. If any one of the four components are missing you will...

Q: Moonroof drain plugs clogged

Hello. This problem is common to Hummer H3s. It is an involved fix, and most of the incidences are related to the front drain tubes, as the vehicle sits at a slight rake to the front. Access to these is...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.