Reduced fuel economy and engine vibration

I own a 98 Civic LX 4 Doorwith about 129500 miles on it. For the past few weeks I have seen the following problems with the car:

1. The gas mileage has dropped from the usual 34 mpg to 26 mpg.

2. When the RPM goes beyond 3100 or so, I feel the engine vibrating differently abruptly and I feel it in my steering wheel. It does not have the gradual increase noise/vibrations as the RPMs increase but a sudden increase in vibration and noise as the RPMs go beyond 3100.

What could be the reasons for the above problems and could they be related ?

Both problems could be caused by a simple ignition misfire. The possible causes of a misfire are myriad.

Start by stopping by the local Autozone and having the ECU checked for stored fault codes. Post them here.

Thank you for the suggestion. I will do that.

Found out that I do not have an Autozone close to my place. So I went to Advance Auto Parts. The guy there told me that unless the check engine light is on, the check would not reveal anything. Meanwhile, I am trying a low cost solution of cleaning the injectors by putting Techron. Will let you know how it goes.

Has the car had basic maintenance?
Things like spark plugs, plug wires, distributor cap and rotor, fuel filter need to be changed periodically.
At this age and mileage the distributor could be worn out.

I would not put the injectors on the top of my list, but possible. I would worry more about spark plugs and wires.

Are you up to date on all the recommended ( That is listed in the owner’s manual ) maintenance?

At this juncture I too would suggest doing the basic maintenance. Plugs, wires, distributor and rotor (if you have them) and filters too. Lots of people ignore the filters.

When the plugs are removed, mark the cylinder they cam from and “read” their condition. A lot can be learned about what’s happening in the combustion chambers by the condition of the plugs.

Post back with the results.

Thank you all for your suggestions. Unfortunately I was in an accident with the car yesterday. A lady cut me off. She got the ticket.

From the looks of it the car may be totalled(this is purely my assessment, I am not sure). The front wheel axles(and may be more parts) are probably bent because the wheels are touching the rear of the wheel wells. One of the tires burst. The frame may be bent. The front doors opened with difficulty and I could see that the panels in front of the doors had caved in. I was not able to look under the hood. My car may not have more than $2000 left on it according to KBB. I am now waiting on my insurance adjuster to come to the body shop and give me the news, good or bad.

Thank you all for being so helpful and making this a wonderful community!! I will update you guys about the new/used car that I may have to get.

In pristine condition, edmunds lists your car for about $3500, so yeah, it’ll be totaled out

I would agree. If the wheels are touching the rear of the wheel wells you can safely bet that all of the suspension components are bent to one degree or the other along with the possibility of a bent subframe or buckled floor pan.

The next step will be the insurance adjuster lowballing you on the value of your car.