98 Mazda Protege Feels like it's going to die at Idle

I have a 98 Protege LX with the 1.5 liter engine.  My car drives fine however sometimes when I stop at a red light or stop sign the engine idle speed drops all the way down like it's going to die, and the engine starts to shake.  The car also does this sometimes when I put it in gear or from D to N.  I changed the PCV valve, cap, rotor, spark plugs, gas cap and wires but it didn't go away.  Also, now that the check engine light is on, it doesn't do it as much but when I disconnected the battery to change the cap/rotor, the check engine light went off and the car felt like it was going die everytime I drove it and then had to stop at a red light or stop sign.  I don't know if there are any new codes but the last time I check at Autozone, all they said was that I had a leak in the vacuum system I believe it was p0455.  Can someone help me please.

A clogged fuel filter can cause the problem you have.  I you haven't done it a few years or 30,000 miles, I would do it anyway, as these cars are a bit finicky on fuel pressure. 
The other thing would be the Idle Air control valve. This is located under the throttle body.  You can test it with the ignition switch off, then measuring the resitance of the valve with a multimeter.  The resistance across the valve should be 7.7-9.3 ohm.  If out of that spec, it should be replaced. 

with the 1998 proteges, is the fuel filter in the fuel tank or under the hood anywhere?  im looking to change mine and want to attempt doing it myself if it isnt all that tough.  thanks

I actually already changed the fuel filter.  It's in the back by the firewall.  You can get to it from underneath the car.  Thanks for the other suggestion.  I will try that. 

my car is the exact same way.  i have a '97 protege, 1.5 DOHC, and only at a stop and idling does my car get like that.  i let it go so long that i ended up changing my engine mounts that got torn but i'm on a mission to get it fixed immediately.  please let me know what you find.  i find that with the a/c off, the problem is there but not so bad as when i turn the a/c on, then it gets very bad.  Either way, when i come to a stop and am idling i'm having some terrible vibrations as the engine struggles to stay alive.  i just did a complete overhaul including a head job so i was hoping with all the new parts that problem would be addressed but not to be so lucky.  it's still there.  i haven't tried changing my fuel filter even though i purchased it already and i did not check the idle control valve resistance but i'll be doing that immediately.

Ok I tested the IAC valve this morning and it had an ohm reading of 8.5 so I guess it's good.  I'm lost again.

Have you considered taking the bus?

Sorry, I couldn't resist. Anyhow, have you tried cleaning the choke and mass air sensor? What about the air filter? Have you tried adding a fuel system cleaner to the gas?

I have a 98 Protege with a 1.5 and manual transmission which does the same thing, it will also do it after you have started the car after it has been running for a while - goes to a really low idle like its gonna die and shakes pretty good then the rpm picks up and smoothens out.
I did a full tune up - new plugs, wires, cap and rotor, fuel filter etc, and it still does it from time to time.
The check engine light is on and it gives codes p0120 Throttle position sensor, p0421 warm up efficiency bank 1 (o2 sensor?), p0455 evap system leak large.
It's likely a combination of the above codes so I'm going to put in a new TPS and o2 sensors and see what happens, I will have to trouble shoot the evap system and see where the leak is.

I have a 98 mazda protege 1.5 manual transmission. I'm getting a rapping noise from the motor when the car gets up to 2 rpms, and when I come to a stop the car wants to die. I've done an oil change, tune up, Timing belt, and fuel filter and still have the same problem. I was hoping some one might have some answers before my mechanic has replaced everything possible.

Have you checked your battery lately? Is the problem worse when you are running a lot of accessories (lights, stero, fan, rear window defroster)? If so, a marginal battery could be the issue.

Had the same problem (97 Protege) Had to put it in neutral at stops just to keep it from dying. My problem was the large ribbed hose coming from the air filter box was cracked. Temp wrapped in duct tape cleared up immediatly. Runs perfect Now !

Its a new battery, The car will start out fine no problems with the first couple of stops then when I go to come to a stop and push in the clutch
the car starts to idle very low and acts like it wants to die. A couple of times the car has died in the middle of traffic. Also when this starts the oil light on
the dash starts fluttering off and on.