I am a first time poster here. I have on 06 mazda 3 2.3l with auto. The engine has a rough idle. Is has no check engine codes reading. My gas mileage and performance have not degraded at all. I changed plugs (they were pretty clean). I looked at the throttle body intake, it is clean. The car runs like a top except for the rough idle. Any suggestions?

 

Has it been rough forever, or just started? I'll assume its been there all along and you have to sort of live with it.
Mine vibrated at idle, and has done it since day one... it improved a tiny bit after stiffening the engine mounts. I added silicone to keep the engine from moving as much since the manual i've got has a lot of movement when starting off.

If it's a new issue or very rough, it could be an engine sensor, bad gas, dirty fuel injectors or something like that. Fuel system cleaner is the easiest thing to try - it's really just mineral spirits mixed into the fuel as a solvent - look it up online for concentration information.

 

nope, it was very smooth up till about 5000 miles ago. I used fuel injector cleaner, did nothing. If I put the car into neutral it smooths out completely. There in no other driveabily issues at all, it revs smooth all the way to 6500 RPM, and never hesitates. I use good gas the vast majority of the time.

 

Is it just the idle dropping when in gear or is the roughness more than just low idle? Did you do any work around 5k miles ago? If there's an air leak in the intake that could cause rough idle according to the manual.

This note is to correct idle drop when the A/C is cycling - could be related to the issue you're having if it hasn't been updated yet. See http://www.finishlineperformance.com...39-07-1842.pdf

You may have to wait and see if it gets worse and therefore turn on the check engine light. Or have it looked at by a shop, the dealer may have some information on a common cause of this kind of issue.

 

I had rough idle on my 2005 2.0l 3. Found a service bulletin online describing symptoms as rough idle or even engine stall after stopping.

Basic solution is to remove the throttle body and fully clean it. the engine side of the throttle was covered with very hard carbon deposits. This interferes with the idle air flow when the tottle is closed.

After cleaning with cleaning spray it looked like I bought a new replacement throttle body. bolted it back on and car ran like new.

In my case the rough idle started slowly and got worse as I put more miles on the car until it died on me today. No CEL either.

Hope this helps

 

Excelent, thanks for the info... i've cleaned my throttle body a few times when doing other maintenance so it never got plugged - good to know there is an easy fix for this.

 

Leave the car run in park for 20 mins dont touch anything after 20 mins turn ac on full blast for 20 mins this simple trick fixes the problem 90% of the time