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

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Battery draining.

Either your battery is due for replacement or you have a parasitic draw somewhere. A draw can be found by placing an ammeter in series with the negative battery cable. If excessive current draw is found, the cause of the...

Q: After part replacements, spark plugs do not work - 1996 Lexus LX450

If you have a Check Engine Light on, first check for those codes to determine what engine management thinks is going on. If no trouble code, check the ignition fuse behind the driver side kick panel (carpeted panel at foot...

Q: Intermittent issue where after a stop car is stuck in first, speedometer at zero. Had output speed sensor changed, no change.

Hello there, a few possible faults could cause the vehicle to become stuck in first. The most common would be low fluid level, shift solenoid, transmission range sensor, or a transmission mechanical fault. I'd suggest getting this looked at by...

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...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.