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?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. 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: My high beam light does not work on left side. I don't think it is the bulb.

Hi there. There could be an issue with the high beam switch. Check to make sure that the wires are connected correctly to the high beam switch. Also, check the bulb in the high beam on the left side. See...

Q: Q: My car won't stay on

Hi there. Assuming the backfiring was taking place prior to replacing the spark plugs and spark plug wires. This would lead me to believe there is a valve train related issue. Possibly, a broken intake valve spring. This would account...

Q: Q: overheating problem

Thanks for writing in about your Hummer H2. Let's cover the basics of diagnosing a overheating issue. First, verify the actual temperature at the thermostat housing. Cooling system (and cap) has probably been pressure tested by now. If it tends...

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...
How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...