> 1) Is that the only one reason this could happen, or could it be
> something else too?

Normally, a vac leak would send the computer into full rich mode. When
the computer sees that you are not going above 30 when the throttle is
wide open (or depressed to the floor) and rpm is not rising above 3000
rpm (guessing) then computer will usually set a fault code. If you
have no codes then the problem likely isn`t fuel mixture. Maybe
timing, low compression, poor ignition, etc.

Did anybody tampered with timing? Did anyone overheated the car?
Tune-up your ignition lately? Autolite spark plugs won't last long but
it usually gives you the extra need horspower - a 3 mph gain (IMO).

> 2) What do I do to fix it? I dont know much about vacuum leaks but is
> it a expensive job?

A vac leak is recognised by a hissing noise. Spray a mist of water
into the hiss or any other suspected areas and sound will change,
including motor sound. No change in sound, it's not the problem.

> 3) I would be changing the time-belt of my car. Is there anything is
> specific I should ask the dealer to change too, keeping this problem
> in mind?

Don't leave until they adjust the timing!
K

> > | My car (1990 Honda Accord, Auto, 142K, 4 cyl) runs good otherwise.
> > | Only when going up slope, it is kind of slow.. doesnt go more than
> > | around 30mph. It feels kind of uncomfortable when going up slope.
> > | Can anybody please tell me what could be the reason ? And is there
> > | anything that I could do to improve on this? I know that it is a
> > | pretty old car and it has its own limitations, but any suggestions
> > | would be appreciated, especially since I am soon going to spend some
> > | $$ on replacing its time-belt.
> > | Thanks in advance!
> > | QGoogle
> >
> > Had the same problem years ago with an old Dodge Colt. In that case, it was
> > a vacuum leak that only manifsted itself when the throttle was opened up.