random drop in idle

Hi there, I have a Mazda Protege 5 2002 and for about a month when at a stop in gear or not the idle after a little bit will just start dropping and then like catching and then raises up to normal and then drops again. Over and over until obviously I start going again. Get to the next stop light. Sit for a second at normal idle then bam, it drops and repeats the same issue. Any ideas before I take it to the mechanics.
 
Do you have a CEL yet? I have the same issue right now but my CEL didn't come on for a few days after it started.
 
I did but i just got a gasket from the exhaust system replaced today and i think that was causing it. They cleared it. If it comes back then I can go from there. It was lean code.
 
I feel like that wouldn't cause a lean code, but maybe I'm wrong. Right now I have a lean code and eval leak code (p0171 and p0455 respectively).
 
This happens to me from time to time while driving, but it's pretty intermittent. I only notice it consistently happening when I drive either to / from work about 25kms / 40 mins. When I finally get to my parking spot (either at home or work) and have gone idle, the rpm dips from 500 to sub 250, almost like it'll stall but it picks itself up again and goes back to normal idle which is 5-700.

Never had CEL before, the only mods I have are short ram intake and an mp3 ECU. But this tends to happen even way before I had the ECU. I'll try cleaning the MAF and see if it still occurs. OP, have you tried the same?
 
Vac leak, dirty maf, dirty iac, clogged EGR, failing plugs, etc.

he hit it on the head here, those are the big things to look for, check your air filter cleanliness as well( this may not be causing the issue but if anything it will help) also check your intake hose for rips or cracks mine was doing that and i found a crack in the flex ribs that was letting in air begind the MAF, replaced the hose and bam fixed.
 
he hit it on the head here, those are the big things to look for, check your air filter cleanliness as well( this may not be causing the issue but if anything it will help) also check your intake hose for rips or cracks mine was doing that and i found a crack in the flex ribs that was letting in air begind the MAF, replaced the hose and bam fixed.

Same here. Found a crack in the hose behind the MAF, replaced, reset and fixed.
 
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