so, i have a 2000 protege with the 1.8 L, 5 speed, with about 95,000 kms or 60k miles. about 2 months ago my check engine light came on for the first time. i choose to ignore it. after a while my engine began to idle extremely rough. when at a light the rpms will drop to 100-300 then climb back up then back and forth, when the rpms drop its as if the engine is going to stall out(but it never has). so i decided to scan the obd II and see what was up. i dont remember the code # but it said running lean and that the problem was recognized at bank 1. after thinking for a while and talking to a couple friends i decided that there was a good chance i had a faulty O2 sensor. so i changed the upper/front sensor.

i just did this today and after resetting the codes my check engine light has yet to come back but the idle issue is still there. i think the light needs more time and it will be back.

any ideas or people in a similar situation would be appreciated. i live in a harsh climate and wanna fix this before winter.

 

My wife's Mazda Protege 1.8 had the same issue. Code P0171. Rough idle. I changed the MAF sensor. No luck ($190). I sprayed some carb cleaner around the top of the intake manifold and found it's leaking in the center area. I have heard that this is a pretty common problem. I put a bandaide fix and sealed the area with RTV until I have the time to change the gasket. It worked for a while but the leak comes back.

 

I have similar problem you described on my 99 Protege 1.6. Everything is pretty much the same as your 2000 Protege except for smaller engine. Dealer did the code check for me and it turns out to be mass airflow sensor, maybe you guys can try that. They are kind expensive though, the stupid sensor is around $200-$250 range. And is easy to replace yourself, it should be right next to the air intake hose coming out of where air filter is at.

 

I typed MAP originally but meant MAF. I already replaced it and it didn't fix the problem. My issue is a leaking intake gasket. I have heard that it's a known problem on the 90's-00's Mazda 1.8 and maybe others.

 

Ah ok, I guess I m no help then. I am not sure if this is a common problem or not, but my 99 Protege never have any of that problem until my MAF die at around 130K miles. BTW, that is the only thing evercostme a repair for my car so far. Other than that, it just straight out regular fluid change, tires, brake pads, filters (the typical regular tune up stuff). I am actually surprise to see so many have issues with their protege. Maybe I m just a few of the very lucky ones that don't get problem onmy protege.

 

Did you ever figure out what was wrong -- mine is doing the same -- only it is a 2003 6

 

check the air intake hose leading from air box to the engine. move the hose by hand and inspect for cracks. If cracked (usually near engine) , the engine will idle fine , but........... when engine is torqued by driving , the crack in hose will open and send lots of air into engine manifold . This really confuses ECM and throws CEL codes and runs poorly. It's an easy check , tape is a band-aid approach, inexpensive to replace.