2009 Mazda3 odd low idle

[Johan1]

Hi everyone, got another mechanical question

My 2009 Mazda 3 2.0 has this odd low idle issue which I can't pinpoint. Once the car is fully warm, in P, R and N, it will idle normally around 750rpm, but when in D, it will idle at 600 (sometimes down to 500) only IF my foot is on the brake. I pulled the e-brake while the car was in D and let my foot off the brake, and the idle went back to 750rpm... as soon as put my foot on the brake, back down to 600 it goes... however, if I turn on the fan to max, the idle stays at 750 while in D and foot on the brake. Same thing if I turn the AC on.

On top of this, I was having a hard starting issue after filling up the car, and what seems to me as poor fuel consumption, but can't say if the idle and these issues are related or not

The hard starting i've read is common, and can be the purge valve solenoid or gas cap. I tested the purge valve solenoid by removing it and giving it power, and nothing happened, so I concluded that it's likely bad and replaced it. I also threw in a new gas cap since it was cheap, went to fill up, and didn't have any starting issues, so I believe that issue is now fixed. As for the fuel consumption, it's around 10 L/100km (23 MPG), which is hard to say if it's normal or not given the weather is now colder, and the car does sit a lot in heavy city traffic before getting onto the highway.

I also cleaned the throttle body since it was all gunked up, and cleaned the MAF, and the spark plugs are new NGK iridiums. Needless to say, none of these things solved the odd low idle... so the only thing I'm left with at this point is to do an idle relearn since i've heard this can be caused by disconnecting the battery (although I never have since owning the car).I won't get a chance to do that until the weekend probably, and if that doesn't solve it, i'm not sure what it can be, other then possibly the evap canister that sits under the fuel tank, which is a pain to get to.

Also, for what it's worth, the rad fan kicks on constantly even now with temps around 0 degrees Celsius, which is odd... I checked the coolant temp and it's right on 87-88 degrees Celsius, and no coolant leaking anywhere... again, no idea if this could be related to the low idle.

 

[CharlieJ]

Is this “low idle“ causing a problem? How are you verifying the RPM? The tach needle may be a little off.
My Mazda 3 with the 2.3 Automatic trans idles down to 600-580 RPM in drive with foot on brake. And idles up to 720-700 RPM in neutral/park. Verified with a Scanguage II. (This is all with the A/C OFF, the engine will idle higher with the A/C on in order to Turn the compressor)
As far as the fan, it seems to cycle on and off whenever the A/C is on no matter what temperature it seems.

 

[Johan1]

Sorry should've mentioned I verified the rpm with a generic obd via Bluetooth and torque app on my phone. It hasn't particularly caused any issues yet, but I have noticed a few times the engine bog, as if it wanted to stall, seemed like it miss fired for that moment when it bogged, but hard to say. As for the fan coming on, mine comes on without the ac, when it's cold outside, which seems really strange and definitely not the norm in my mind

 

[CharlieJ]

I remember reading that a clogged or partially blocked EGR valve could cause issues when idle. You can look into that if nothing else seems to work. That fan running does not seem normal.

 

[Johan1]

Now that you mention the EGR, I just remembered that I had seen a couple videos regarding that...that's another fun part to access on the car. For now it doesn't seem to be causing any issues, so i'll monitor and see what happens, possibly tackle an EGR cleaning at some point

I'm hoping that the purge valve solenoid and new gas cap at least solved the hard starting issue after filling up, and as for the fan, yea don't know what to say... car isn't overheating, so again, one of those things that if nothing bad is happening, just let it be I suppose... I'm more so curious to try and understand what's going on

 

[PimTac]

My 2017 Mazda SkyActiv idles at a standstill at 550rpm but will cycle to 700. I think this is the computer controlling the idle for emissions purposes aa sensors read the exhaust output and send signals.

I know yours is not a SkyActiv but it could be a similar situation unless this is really sporadic.

 

[Johan1]

Interesting to know, the idle on my car is consistent at 750ish in D with foot off the brake, and 600ish with foot on the brake, all the time. I guess the only other tid bit is this only happens once the car is fully warm, so something like what your saying about the computer adjusting for emmisions is possible, although I have never seen it on any other car I've owned. None the less, as mentioned, at this point there isn't a whole lot I can do without any other symptoms, so I'll monitor and see if anything changes in the future

 

[Johan1]

Going to bump this thread since I don't want to start another one. The low idle is still there, but the hard starting after fill up is gone so at least I fixed one issue

Now, I'm a little more concerned about the fan continuously coming on with freezing temps outside... I noticed that the heat on full blast blows warm, but by no means hot... It's enough to get warm in the cabin that you won't freeze, but it will not get scorching hot like my other car...and, with the fan on max speed and heat, the radiator fan stops coming on. Again, no codes on the car, and the coolant temp shows 87-88 Celsius, so car isn't overheating, and it did not overheat in the summer with hot temps either... Not sure what this could be, but I'm thinking that coolant is getting too hot somewhere, hence the rad fan is coming on even when cold... It's not leaking coolant, so I don't suspect a water pump, although I imagine it could be, and I wouldn't think it's the thermostat given the coolant temps reads in the normal range, although I've heard that's also a possibility... Thoughts? Not sure what else I can do to pinpoint the issue without any codes, leaks or obvious faults (other then lukewarm heat in the cabin)

 

[mk378]

Is the coolant full? If it's a non-pressurized tank system, check in the radiator not just in the tank.

 

[Supersonic]

What's telling the fans to be in the ON position? The correct diagnosis probably starts with that question. I had a 1988 Chevy Nova (Corolla) that the sensor was unplugged and the fans stayed on all the time, that's the short version, once plugged back in the fans went to normal cycles. Now as I understand this has an ON condition only at cold temperatures. Look over all the related wiring and a wiggle test may help. Knowing the parameters of components like the temp sensor and testing for limits is sometimes easy, but next diagnostic steps may involve a wiring diagram and I found that isn't always so easy to find, so...

The parts changer in me would change out the coolant temperature sensor, and I think there could be 2 possibilities, one in the block and 1 in the radiator. Then I would change the thermostat. May also be a fuse to inspect. In some circle parts changing isn't popular, but it's good when it works and you may not have many other options to pursue. The thermostat may not be original and could possibly be the alternative temp, meaning about 10 degrees cooler than OEM.

Another clarification may be needed on the rad fan, does it stay ON constantly or does it cycle OFF and ON constantly? Not that I have the answer, there are likely others that have more insight given this information.

 

[Johan1]

Coolant is full

Rad fan cycles ON and OFF all the time, verified visually (although it's quite audible too). The cycle of the rad fan ON and OFF happens when the cabin fan is on its lowest settings, however, when I switch the cabin fan to max (position 4 on the climate control knob), the rad fan no longer cycles ON and stays OFF the entire time. Yes, one of the engine coolant temp sensor could also be the culprit, but given that the rad fan does not come on with the cabin heat on full blast, I concluded its likely not the culprit (although doesn't mean it can't be, I'm not sure), and yes supersonic I agree, I'd like to try and diagnose this properly before I start throwing parts at it

 

[Supersonic]

I wouldn't fault throwing parts at this, well as long as it's cheap enough. Looked up the parts on Rock Auto and find there is a cooling fan control module attached to the fan assembly, there is also a short video here at the part info link that may add some context to the system. If you got a local junkyard and can get the module or whole assembly cheap, that could be a good option, though if the Rock Auto ~$100 isn't to far above budget and everything else has checked out, if you can't find specs for testing the module, I'd just replace the whole assembly and cry if I was wrong...Assembly was priced at $25 for some local junkyards around here, https://www.car-part.com/, I used this many times to search the local junkyards.

Though I'd first see what I could find out about the module testing, at least in a generic sense power and ground being obvious. I see on the Rock Auto image display there are 2 terminal at that connection, might it have a spec for the limits of the internal resistance? Someone else best answer anything about the module, I really have no experience there.

And there is also a part listing, cooling fan control module WVE 6H1518 that talks of relays, something I don't have a lot of experience in, but a YouTube Search on all these may help at least in understanding the system and what to do for checking relays.

Also for Ebay Search part numbers are usually good but I also like a generic like '2009 mazda 3 fan control module' to see if I can get something even cheaper, but really some sellers just don't come up with part numbers. Also checking Amazon for price deals can lead to an acceptable component.

I also see this 2.0 references on eBay to be something that may also be Ford Focus related, I don't know and briefly looked it up on Rock Auto but the fan assembly was different in the 2009, but the newer ~2012 or 2013 started to look similar. Just another path if you are running out of options.

 

[Johan1]

I wouldn't fault throwing parts at this, well as long as it's cheap enough. Looked up the parts on Rock Auto and find there is a cooling fan control module attached to the fan assembly, there is also a short video here at the part info link that may add some context to the system. If you got a local junkyard and can get the module or whole assembly cheap, that could be a good option, though if the Rock Auto ~$100 isn't to far above budget and everything else has checked out, if you can't find specs for testing the module, I'd just replace the whole assembly and cry if I was wrong...Assembly was priced at $25 for some local junkyards around here, https://www.car-part.com/, I used this many times to search the local junkyards.

Though I'd first see what I could find out about the module testing, at least in a generic sense power and ground being obvious. I see on the Rock Auto image display there are 2 terminal at that connection, might it have a spec for the limits of the internal resistance? Someone else best answer anything about the module, I really have no experience there.

And there is also a part listing, cooling fan control module WVE 6H1518 that talks of relays, something I don't have a lot of experience in, but a YouTube Search on all these may help at least in understanding the system and what to do for checking relays.

Also for Ebay Search part numbers are usually good but I also like a generic like '2009 mazda 3 fan control module' to see if I can get something even cheaper, but really some sellers just don't come up with part numbers. Also checking Amazon for price deals can lead to an acceptable component.

I also see this 2.0 references on eBay to be something that may also be Ford Focus related, I don't know and briefly looked it up on Rock Auto but the fan assembly was different in the 2009, but the newer ~2012 or 2013 started to look similar. Just another path if you are running out of options.

Thanks for the info, I did look into the fan control module, but it seems like on this gen mazda, the assembly is as a whole fan unit, so the module is integrated into the fan and there is no separate part for sale (the rock auto parts are generic units, not mazda specific)... kind of stupid, my 02 jetta tdi has a separate fan control module, which sits under the battery, and is just a box with 2 connectors which is easy to replace, and cheap... I know because I had to replace mine, as the AC would not work, and the fans would not kick on... while on the mazda I doubt it's that, I could easily source and entire fan assembly from a self pick scrap yard not far from me, at a cost of 30 CAD and swap it in and see if that makes a difference, or, looking on youtube videos, It seems like the module may be removeable from the fan assembly, so again, would go to the yard, remove the fan assembly, and then just take the module off and that would be 20 bucks. I will most likely wait a few months at this point since the weather is cold and without a hoist some of these jobs are pain to do on a cold ground... but if I can try and get ahead on diagnosing, that would be a good start. Thanks for the help thus far

 

[windeye]

Is this “low idle“ causing a problem? How are you verifying the RPM? The tach needle may be a little off.
My Mazda 3 with the 2.3 Automatic trans idles down to 600-580 RPM in drive with foot on brake. And idles up to 720-700 RPM in neutral/park. Verified with a Scanguage II. (This is all with the A/C OFF, the engine will idle higher with the A/C on in order to Turn the compressor)
As far as the fan, it seems to cycle on and off whenever the A/C is on no matter what temperature it seems.

I have a 2007 with 2L engine. What you described is what I have observed as well. Seems to be normal.

 

[windeye]

Sorry should've mentioned I verified the rpm with a generic obd via Bluetooth and torque app on my phone. It hasn't particularly caused any issues yet, but I have noticed a few times the engine bog, as if it wanted to stall, seemed like it miss fired for that moment when it bogged, but hard to say. As for the fan coming on, mine comes on without the ac, when it's cold outside, which seems really strange and definitely not the norm in my mind

The fan comes on when you have your hvac mode dial pointing to floor and window (from 12 o'clock position to 5 oclock). The AC comes on automatically for those positions without having the AC indicator lit.

 

[Johan1]

The fan comes on when you have your hvac mode dial pointing to floor and window (from 12 o'clock position to 5 oclock). The AC comes on automatically for those positions without having the AC indicator lit.

Ohhh, now that, I have never heard of on any car... Ac coming on without you physically turning it on. That is very interesting, I will switch the HVAC mode and see what happens later today as I would have never thought of that

 

[PimTac]

Ohhh, now that, I have never heard of on any car... Ac coming on without you physically turning it on. That is very interesting, I will switch the HVAC mode and see what happens later today as I would have never thought of that

That’s common these days. If you select a
window defrost position the A/C comes on. You should be able to hear the compressor come on and off.

It happens too with automatic climate control.

 

[Johan1]

That’s common these days. If you select a
window defrost position the A/C comes on. You should be able to hear the compressor come on and off.

It happens too with automatic climate control.

I worded my previous reply incorrectly. I have noticed that turning the HVAC to a certain setting turns the ac on, but I only noticed this in the summer whenever I set the temp to max cold, the ac would turn on, and the corresponding light would also go on, but I have never heard of the ac turning on its on without the corresponding ac light illuminating in the car. Anytime I have seen the ac come on after picking a certain hvac setting, the corresponding light inside always turned on to indicate ac is on

 

[PimTac]

I worded my previous reply incorrectly. I have noticed that turning the HVAC to a certain setting turns the ac on, but I only noticed this in the summer whenever I set the temp to max cold, the ac would turn on, and the corresponding light would also go on, but I have never heard of the ac turning on its on without the corresponding ac light illuminating in the car. Anytime I have seen the ac come on after picking a certain hvac setting, the corresponding light inside always turned on to indicate ac is on

On my ‘17 CX5 if I have the climate control set to 70 and it’s 40 outside for the morning start the A/C comes on at the beginning to help clear the windshield. The system does what it wants to do. Sometimes I don’t understand it but it’s using the input of sensors inside and out to determine which setting and direction things go.

The one thing I don’t care for is that the fan speed goes up at the beginning. That’s to clear the glass quicker. Later it slows down.

Mine may be totally different than yours though.

 

[GMFan]

I had an idling issue on my 2011 Mazda6.

Thread below:

Car struggles to idle without stalling

2011 Mazda6, MT, 147k miles. For the past week my car has been idling at too low of an RPM (currently idles around 500RPM but typically idles at 750RPM). The engine seems to be trying to avoid stalling out by raising the RPMs when the RPMS drop too low. The car will vibrate/gently shake like its...

bobistheoilguy.com

It drove my absolutely nuts. The dealer kept the battery disconnected for over an hour and did a top end de-Carboning using something like sea foam. Apparently the pistons and some of the internals were carboned up. I think the used a mini bore scope camera to verify. Since then the issue has not returned.

It’s been “fixed” now for the last 10k miles. Now almost at 165k.

See last post in the thread I linked. My Mazda dealer called it an ‘EFI service’ which included cleaning the injectors and de-carboning the top end and manifold. Apparently after 150k miles carbon can really take its toll.

A clogged fuel injector can really cause tons of drivability issues. During my ordeal I never once got a CEL light.