O2 Sensor and spark plug gap issue / MPG

[tjkenny15]

Thought I would share my current experience with the forum; I recently had a rough idle and a check engine light that flashed on because of it. It happens that the O2 sensor had failed at 2,400 miles and was causing a rough idle when the engine would be cold. The check engine light would randomly come on, never stay on.

At first I thought it might have just been the spark plug gap on a couple plugs being off, the Chevrolet dealership in Owings Mills said that was highly unlikely with it being a brand new car. The dealership replaced the O2 sensor after running through the codes and the car ran noticeably smoother. Now I was seeing 35 mpg instead of 32mpg under similar driving conditions.

The car still didn't seem as though it was running at its best. After work a couple days ago, I checked the gap on the all plugs. A couple were at 24mm and the other couple 27mm. I changed them all to 28mm with a proper spark plug gaping tool. A seriously noticeable difference after doing so. The car had a smooth idle and gas mileage may have improved slightly, hard to tell.

The whole point of my rant here is to share my experience with the O2 sensor, the plugs being slightly off and the fuel economy difference. Hope this may help others that are experiencing relative issues to investigate opcorn:

 

[BuckSonic]

Similar experience - CEL, dipstick seating, spark plug gap

2012 Chevy Sonic LTZ 1.4 turbo 6MT put into service July 26, 2013

Check engine light (CEL) triggered at 500 miles reporting low voltage to O2 sensor. Service manager said this was common and re-set it without any repairs.

Car was serviced at dealer at 7400 miles: oil/filter change and tire rotation. While driving home CEL came on again and engine was running rough and stalling. Once home I looked over the service work and discovered the dipstick was not fully seated. Of course, I could not tell whether the technician failed to seat it properly or engine pressure dislodged it. I seated the dipstick.

Returned car to dealer two days later. Service manager said there were four CEL codes this time (O2 sensor, MAF, air flow, etc.). Tests revealed nothing. Nothing was fixed and the CEL was re-set again.

I am hopeful that this second occurrence was caused by the dipstick not being seated by the technician.

Reading this forum had piqued my curiosity regarding spark plug gaps and CELs. So today I pulled the spark plugs. All four were at 24mm, so I opened them to 28 mm per GM's recommendation.

Prior to this I've been averaging 42 mpg on the optimistic instrument panel read-out (mostly highway driving). I will report if my mileage increases as a result of re-gapping. If there is a drivability improvement, it is minor. There is little point revving the engine past 4000 rpm and it's fairly gutless at low rpm. The engine's happy place seems to be 1800 - 4000 rpm.

 

[Chrish051873]

2012 Chevy Sonic LTZ 1.4 turbo 6MT put into service July 26, 2013

Check engine light (CEL) triggered at 500 miles reporting low voltage to O2 sensor. Service manager said this was common and re-set it without any repairs.

Car was serviced at dealer at 7400 miles: oil/filter change and tire rotation. While driving home CEL came on again and engine was running rough and stalling. Once home I looked over the service work and discovered the dipstick was not fully seated. Of course, I could not tell whether the technician failed to seat it properly or engine pressure dislodged it. I seated the dipstick.

Returned car to dealer two days later. Service manager said there were four CEL codes this time (O2 sensor, MAF, air flow, etc.). Tests revealed nothing. Nothing was fixed and the CEL was re-set again.

I am hopeful that this second occurrence was caused by the dipstick not being seated by the technician.

Reading this forum had piqued my curiosity regarding spark plug gaps and CELs. So today I pulled the spark plugs. All four were at 24mm, so I opened them to 28 mm per GM's recommendation.

Prior to this I've been averaging 42 mpg on the optimistic instrument panel read-out (mostly highway driving). I will report if my mileage increases as a result of re-gapping. If there is a drivability improvement, it is minor. There is little point revving the engine past 4000 rpm and it's fairly gutless at low rpm. The engine's happy place seems to be 1800 - 4000 rpm.

Just clearing the code is not fixing the problem, and for them to do it multiple times, shame on them.

Find another dealer next time it comes on, there could even be a code stored without a CEL coming on.

Seems there have been a few members having bad luck with a dealer recently. :sadbanana:

Chris

 

[ss2000slp]

Kind of a long haul for you, but Carter Chevrolet in Manchester has been pretty good.