Have a 2001 Civic DX, Manual Transmission, 228K miles. 1.7L SOHC.
Recently changed front motor mount and timing belt on the same day.
I noticed the car running rough and is only rough at certain RPM. Here are the rpm ranges it runs rough, 700rpm which is idle, 2200-2400rpm and 3400rpm approximately. It idles at 700rpm which I believe is the idle rpm on my car, so thinking my timing is not off. One more thing I noticed is if I have AC on and reving down in rpm it sounds like it is about to shutoff (never shuts off) and get a stronger vibration and same thing when I turn the AC on at idle. With ac on my rpm are 720rpm give and take a few. I been driving with above symptom for 300mi+ so far, even got it upto 95mph, don’t know if it is an indication of anything. Got new spark plugs installed at 220K miles.
Could it be the motor mount or my harmonic balancer is out of balance. I did have to use 3/4" impact wrench to knock the harmonic balancer bolt loose. It is a little rusty given I got 228K miles on it.
I am just dreading the thought of my timing being off by a tooth, me and my friend checked the timing marks per oem manual, he checked the cam shaft pulley marks and I did the crankshaft. When we installed the timing belt I only turned the engine counter clockwise so I would not cause a problem with timing belt slack. My AC belt may be a little too tight as well.
The motor mount I put in was an aftermarket one that I bought from amazon. But I have put in aftermarket mount before on the same car and never had anything like this. I am planning to loosen the motor mount, shake the engine, tighten them back up and see if it makes a difference. May be the engine is not seated properly.
Any help will be greatly appreciated.
Sorry for writing a novel but wanted to give the whole story.