I just purchased a 98 Mazda Protege LX 5spd, actually about 2 weeks ago. I bought it with a bit under 63400 miles on it, and at first it ran fine, but after driving it a while, I noticed rough idle speeds, especially when braking. The idle speed never stays constatnt, and it keeps on fluctuating slightly as it idle's. The idle speed tends to drop as I brake, and after a while it evens out. I've read the threads here and found some advice, but as far as the dealer told me, all mantainace has been done on the car, so the fuel filter might've been replaced, everything else seems to be OK upon inspection, dosn't seem like there is any leaks. I have noticed when started cold with the hood open I could hear a hissing sound, I didn't have time to wait for it to warm up to see if it went away, and never had a chance to check it again.

I've read the Protege FAQ's that are linked here and found a [url=http://web2.airmail.net/emann/protegefaq/tsb/mt000002810.html]Technical Service Bulletin that said EGR valves are stuck open[/utl] ( I won't pretend that I know what that is). Symptoms are simular, but mine also does it when it warms up after a start. If anyone can give me some advice that would be appreciated, since I bought this car from a Toyota dealership and it only has a 90 day powertrain from them, they might not be much help.

 

thats funny, i bought a 98 protege lx 5 speed (pictured) about a year ago with 61000 miles from a toyota dealer, cheap as hell. i've grown to like it more than i thought i would considering its my grocery getter.

i have always had simular idle symtoms to what you described, but no stalls. i dont think its unusual behavior for the car. it doesn't have a very powerful alternater so when you launch a sudden drain using the master brake cylinder or a voltage drop (headlights) you always see it dip then recover once idle compensation kicks in.

if it stall, of course, you have a more severe problem. definately clean the egr valve(s) and change the fuel filter (which couldn't have been mounted in a worse place, behind the air hoses and intake manifold.)

 

I've also had this problem on mine from day one. I remember reading a solution on Protegetech Group. A guy there bought some stuff called "Ignition Protectant" and sprayed it on his wires, cap and maybe the coil too, but I'm not sure about that. He said it worked.

 

if that bandaid fix worked, then obvious there is something wrong with the ignition system.... it is arcing somewhere to cause a misfire

 

just went through the same stuff with my last ride..check the o2 sensor, MAP sensor, TPS, and it could simply be air in your coolant system, just bleed the fluid.

 

Forgive my ignorance, but how the **** could air in the cooling system be the problem???

 

not really posotive of how the coolant could affect the idle, though I had many reliable people tell me to try that. I will get back to you on the relevance.

 

My bosch fuel filter finally came in the other day (cheaper then buying at dealer, and I could only buy fram localy, so I've ordered a bosch online), so today I went ahead and changed it today. It is one bitch to get at, but it's not al that bad of a job. I also partly cleaned out the throttle body, didn't have any degresers with mo so as far as I could get it clean. And the RPMs don't drop As low, they wil drop like 50 or so when braking, but that's normal.

When I started the pro warm today the RPMs were at the stall point, but htey got back up and it was running perfectly fine on the street. When I get some degreaser, or throttel body cleaner, I'll finish that part of the job.

I'll probly clean the egr in the spring when i get a chance, winter isn't hte best time to work on a car without a garage.

BTW, my RPMs don't seem to be steady when the transmision is in neutral, I can hold the gas steady and they flucuate slightly.

 

dID you actually hold the throttle enough to raise the rpm slightly?? I know with mine, even after I tightened the throttle cable, there is still a little bit of play, and if I barely touch the gas (and I mean BARELY) it won't even move the tach needle.

 

I held it steady at like 1500 RPMs and it was fluctuating up and down, never seemed to stay steady. Even with me off the gas, the RPMs fluctuate, just not as much. Seems that the higher the RPMs the more it fluctuates.

 

Funny, that happened today, severely.
I was holding it at about 2000 or so and it idled waaay down and even stalled a couple times.