Idling Rough
 

I have a 2004 Mazda3 w/ 2.3 engine and manual trans. At about 55,000 miles, it began to idle rough. It now has 77,000 miles, and the problem has not gone away, even though I had the following work done: replaced motor mount, ran STP fuel injector cleaner through gas tank, had Mazda dealer do their complete fuel injector/throttle body cleaning, ran a tank of 93 octane fuel through, cleaned the MAF sensor, replaced the purge valve, installed new spark plugs, installed new air filter, and reset the ECU. The Mazda dealer has no more solutions, especially since a check-engine light never came on. But, it is extremely frustrating that the engine continues to shake every time I come to a stop. I have heard some people mention replacing the EGR gasket; however the car has no issues with acceleration. What about the O2 sensor? Is there a solution? Any help would be MUCH appreciated!

try grounding the throttle body.. run a 8-10 gauge wire from a bolt on the TB to the negaive terminal on the bat... also try seafoaming your engine (seafoam is a powerful cleaner, suck 1/3 of the bottle into the vacuum hose on the front of the engine.... it has a red clip its kinda hard to describe, 1/3 of the bottle into the crankcase, and 1/3 of the bottle into the gas tank, then turn the car off for about 30 minutes and start it up and watch the smoke pour out.. thats all the crap that was in the engine coming out) these two things helped the rough idle i used to experience.. also have you checked the passenger side motor mount as you didnt specify which mount was replaced. ummm..... oh yeah, i started to get the rough idle again recently and i had to replace my battery and when i did this it went away( weird) i cant think of any other things to help out at the moment

Thank you for those suggestions, I will try them! I believe it was the passenger side motor mount that was replaced....as it was leaking oil, but that appeared to be a separate problem, and had nothing to do with the idling. When the Mazda dealer did the full fuel injector/throttle body cleaning, they took me out to see the car and started it to show me a ton of white smoke coming out the exhaust, which was supposed to be all of the carbon buildup. Is this basically what the seafoam will do? I did just replace the battery, too, a couple months ago, and that didn't improve the idling. Thanks again for your help!

hmmmm, yeah the seafoam does a very similar thing to what they showed you.. im thinking that they may have just used seafoam lol but try the grounding of the throttle body that may help the problem

Joyworks,

I joined this site because I am having the EXACT same problem with my '04 Mazda 3 with manual tran. My car began a very minor, but noticeable, rough idle at approximately 55,000 miles. I had the guys at meineke do a fuel flush at about 58,000 miles in hopes it would improve this issue, however it did not not and the idling has gotten progressively worse (currently sitting at 63,000 miles). My car will only do this when I am stopped at a stop light for several seconds, take a small dip in RPM's when it is doing it, then seems to correct itself for several seconds, then repeat. It especially does it with the a/c turned off and after I've gotten off the highway and stop for a period of time.

I recently took my car in to a respected car mechanic in my town (Lawrence, KS), and he said he could feel the rough idle at stops, however he didn't think it was outside the norms of my car and believed it was fine (Basically said he couldn't find anything wrong with my car, could/would only be guessing at checking/replacing things to try to fix it and didn't think it would be worth the money).

Anyways, I was just curious (since you last posted in April) if you have found out what is causing this problem. I'd greatly appreciate any suggests from you or others that might know a (hopefully cheap) solution to this issue.

Thanks in advance,

Brad

When I had a 2003 Protege5, the EGR was all gunked up at 50K miles and caused a very rough idle. I would look into the egr. I unbolted mine and cleaned with it with carb cleaner and the rough idle went away.

Would any one happen to know where the EGR is in the 2.3L Mazda 3 engine? I would like to give this a try to see if it helps my idling issues.

I too am having this problem. My EGR valve is believed to be leaking. Anybody have a link to some engine emissions diagrams for the 2.3L?

clean your throttle body and change the plugs ITR6F13 ^ # 4477 when you doing the work make sure your battery is not hooked up.