One more question about knocking or misfire?

[woozlee]

Guys,

I have one more question about my car (1999 Mazda 626 with Manual Transmission, 110k miles on it). I recently replaced my timing belt, water pump, and drive belts. After that, I found that my car had kinda knocking or misfire around 1500 rpm with a high gear (3 or 4) in relatively low speed (20-50miles). If you don't shift down in low speed, you can feel some sort of knocking, right? But it's a little bit different. I felt like my car has a hiccup.

Anyway, so I talked about a mechanic and he said I have to replace the spark plugs and wire. Well, they looked like they have never been replaced. So I let him do that. That reduced pretty much, but my car still has that problem around 1500 rpm, if I didn't shift down at a right time. I can't find what the problem is.

Is there anybody have the same problem and fix it? I hope I can find the way.

Thanks a lot, Jeongwoo.