2005 Mazda 3 Rough idle, loud

SMACKD1

MEMBER
2005 MAZDA 3
4 CYL
2WD
AUTOMATIC
65,000 MILES

I'll try and keep this short but clear. I have the 2.0 version of this car. I changed out both O2 sensors and I'm still having problems with a rough start loud idle and if the fan is on it acts like it wants to stall out sometimes. After an oil change the thing runs likie new but a week later, give or take some days, it's back to its old tricks. Teh air filter is clean and none of the hoses look bad. The main symptoms are the loud engine noise, which is almost constant, the rough idle when it comes to a stop or the foot is taken off of the gas, especially when the a/c or heater fan is on. Any help would be greatly appreciated.

thanks
Stan

5 Replies

KHLOW2008

MECHANIC
41,815 POSTS

Hi Stan,

Thank you for the donation.

Is the Check Engine Light showing?
Did you try to retrieve for trouble codes? Autozone provides free scanning services, get it done and let me know if there are any trouble codes.

About the loud idle that you are referring to, is the engine rpm is high? What is the idling speed then?

Do you mean the engine is surging when coming to a stop?

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Monday, February 8th, 2010 AT 11:37 AM

SMACKD1

MEMBER
6 POSTS

The engine is idling at the normal idle speed, 650-750. It's just really loud and then is loud when you get up to speed. Their is no check engine light and no autozone in Germany and I'd rather stay away from taking it to their shops, price is kinda high. But my main problem is the idle and almost stalling out or acting like it's stalling out especially when the a/c, heating fan is on. I would say it is surging when I come to a stop and/or I take my foot off of the gas

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Tuesday, February 16th, 2010 AT 1:37 AM

KHLOW2008

MECHANIC
41,815 POSTS

Without understanding the type of noise, it is not possible to provide any insight into the problem. It could be idler or alternator bearings ( coarse noise ), ticking noise ( engine mechanical or vlave lifters), screeching ( loose beltings ) etc.

If you are able to provide a clear description of the noise and its occurrence conditions, for me to understand the problem I might be able to provide some suggestions.

As to the erratic idling when stopping, it most probably is due to clogging of the intake passages.

When dirt builds up in the throttle body and Idle Air control valve,, it would restrict the amount of air getting into the intake manifold. When this occurs, the PCM would try to correct the idling, thus the erratic idling. The idling would drop and try to catch as the PCM readjustes itself.

The air passages needs to be cleaned to enable proper air flow and the easiest way to do it is to get a can of carb cleaner to spray into the throttle body and IAC to clear out the dirt accumulation.

Use a piece to scrub the inner port of the throttle body to save time.

This link explains the process in more details though it is for a Honda. Your vehicle is equipped with a MAF so the last part is not applicable as you need to reinstall the air cleaner hose before the engine can run properly.

https://www.2carpros.com/forum/1999-honda-civic-low-idle-vt415479.html?highlight=

By the way, check the hose between air cleaner and throttle body for cracks which would allow vacumn leakages and cause erratic idling.

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Tuesday, February 16th, 2010 AT 2:31 AM

SMACKD1

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6 POSTS

The noise is just a loud engine, nothing out of the ordinary like a belt or anything like that just abnormally loud. I'll check the intake passages and thanks for the help

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Tuesday, February 16th, 2010 AT 3:31 AM

KHLOW2008