popefelix

My wife's car is an 07 HHR LT with approximately 110K on the clock and I recently performed a tune-up - replaced the sparks with new Delco Iridium sparks, put in a new Purolator air filter, and replaced the bolts securing the spark plug boots (1) with bolts from the local hardware store. In the process, I managed to tear the air intake hose (2). I repaired the tear with duct tape.

I buttoned everything up, but accidentally ran the car for a few hours with the MAF sensor disconnected. I then discovered my mistake and reconnected said sensor.

Now my wife reports that the car runs well, but the mileage is down by 3-4 MPG. Could this be a caused by my duct tape hose repair? What about the non-OEM bolts on the spark plug boots? If neither of these, I suppose my next step would be to clean the MAF sensor and run a bottle of Techron through the fuel system, correct?


(1) I had previously owned a car - a Honda Civic - where I managed to break the valve cover bolts while attempting to replace the valve cover gasket. I didn't want to take any chances with this car.

(2) The hose that goes from the fender to the air cleaner, not the hose that goes from the air cleaner to the throttle body.

Oldblue

I suggest you simply disconnect the negative post at the battery for 30 minutes to reset the computers. the MAF sensor being disconnected is most likely the culprit for the mileage issue. the bolts to hold the spark plug coil so long as they are the correct length should be no problem and tha fender to air cleaner box so long as it's sealed up should also be no problem.

donbrew

Why did you replace the bolts?

That may is the problem, they may be too long.

If you tried to gap the new plugs, that is the problem. They are not adjustable and doing anything to them kills them.

donbrew

Learn how to use a torque wrench.

Doc brown

Failure to torque every bolt is not critical. Not using a torque wrench is not going to cause a drop in mileage. I've been working on my own cars for nearly 35 years. I rarely use a torque wrench except when dealing with things like head replacements or transmission work.

Your previous post and Old Blue's are probably close to the cause of the issue.

donbrew

However, the use of a torque wrench would keep one from doing this.

"(1) I had previously owned a car - a Honda Civic - where I managed to break the valve cover bolts while attempting to replace the valve cover gasket."

Wasn't that obvious?