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 October 12, 2016

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.

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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.

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