Idle RPMs drop to 500 when applying breaks at red lights/ stop signs

[vankiz]

Hi guys, I noticed that when I am on a red light or on a stop sign, pressing breaks. My RPMs in 2-5 seconds drop from 900 to 500 RPM.. and stays there until I depress breaks (when I depress, and not touch gas even, it goes up to normal 900 )
It stalled on me yesterday on a red light... Now everytime I stand on a red light I pray and stare at my RPM not to go down and die on me again.

I have a mazda 3 2005 I.
Anyone had this? Whats your RPM on idle and idle applying breaks?

I have disconnected battery and cleaned MAF the other day.. but this started after going under the hood.. maybe touched something .. like a hose.. break booster vacuum leak? any ideas?

[rzapata]

Did you let the car idle for a bit right after you've done all that stuff? I suspect the ECU is just resetting.. After you drive a fair bit, it'll go back to normal.

Other than cleaning the MAF, what else did you do?

[vankiz]

Well last weekend I DCed battery to replace my passenger front fender.. but that has nothing to do with this I am assuming.. Nothing else done.. I mean the first time I noticed this was after first time ever unplugging negative battery.. then was feeling some vibrations at red light.. Never thought of even looking at RPMs at that time.. wish I did.. so, it MIGHT be the ECU taking it time to get back to normal and everything.. does it take long for it to set the settings and everything?

[rzapata]

Yeah, I think it's just the ECU relearning everything.. You're suppose to let it idle for a bit because it'll take a while for the ECU to learn everything again. Maybe 10-15 minutes of driving...

[tmpz]

My car idles at 500 RPM once it's warmed up.

[vankiz]

My car idles at 500 RPM once it's warmed up.

Hmm so 500 is normal on 3's .. then maybe I am overreacting...

[rzapata]

My car idles at 500 RPM once it's warmed up.

Really? Hmm, I thought idle RPM should be in the 700 range...


Hmm so 500 is normal on 3's .. then maybe I am overreacting...

Check this LINK (http://www.mazda3forums.com/index.php?topic=185300.0)out.. Might be helpful, it sounds like a lot of them are having similar problems. Is your car an auto?

[vankiz]

yea, its automatic transmission

[rzapata]

yea, its automatic transmission

Well, the consensus is that it's the PCV valve.. I can't say for sure, but that could be a good place to start... Although, it's weird that it only happened right after you cleaned the MAF...

I would assume that right now, the car still has low RPM at idle even after the ECU reset?

[sp3GT]

It might not be any issue with your car at all. Did you recently put in something new to the car / disconnected battery?

Last year, I installed a HID kit for a member had to disconnect battery for the relay. He leaves my place with everything good. But on his way home, roughly a 20 minute drive he experienced something similar to you. Fluctuating RPMs and also stalled once, I believe it was also an automatic.

After that episode though, the car was fine.

[vankiz]

so all in all... My idle RPMs should technically NOT drop at all after I press the brake pedal on a red light per-say ?

[JSI]

Put the car in neutral, the rpm will go back up.

[vankiz]

Put the car in neutral, the rpm will go back up.

I am sure it would.. but that's not a solution.. I want to fix it :)

[vankiz]

can somebody, who has mazda 3 , 2005, 2.0 sedan. check what they get and let me know, would really appreciate!
See if they get drop in RPM when coming to a full stop while braking.

Thanks!

[vankiz]

can somebody, who has mazda 3 , 2005, 2.0 sedan. check what they get and let me know, would really appreciate!
See if they get drop in RPM when coming to a full stop while braking.

Thanks!
Automatic transmition

[Ozil]

Hi guys, I noticed that when I am on a red light or on a stop sign, pressing breaks. My RPMs in 2-5 seconds drop from 900 to 500 RPM.. and stays there until I depress breaks (when I depress, and not touch gas even, it goes up to normal 900 )
It stalled on me yesterday on a red light... Now everytime I stand on a red light I pray and stare at my RPM not to go down and die on me again.

I have a mazda 3 2005 I.
Anyone had this? Whats your RPM on idle and idle applying breaks?

I have disconnected battery and cleaned MAF the other day.. but this started after going under the hood.. maybe touched something .. like a hose.. break booster vacuum leak? any ideas?

same problem! my car stalled 3 times within a month...

my rpms drop same way you described

[m_bisson]

Can you set the vents to floor only and see if the problem still occurs? Reply back :p

[vankiz]

Can you set the vents to floor only and see if the problem still occurs? Reply back :p
Strange thing, it drops still but from 900 to 750 I would think instead of 500.... and vents make strange noise... any ideas?

[highlineMotors]

I've heard of cases like this while working at the dealership. First off, you should get it scanned to see what codes you may have. I know there's a TSB on bad fuel pumps, don't know if it applies to your model. A fuel pressure test should be done on the vehicle. If it doesn't hold pressure, you have a bad fuel pump. If you get code P2187...likely a bad purge solenoid valve to start off with. I replaced the fuel pump and a purge solenoid valve when I saw this case. Hope that helps. Let me know if or when you get it fixed. Cheers.

[vankiz]

asked a friend to scan me for codes.. he found nothing .

[awhoy]

I had a similar problem on my 05. Had the purge solenoid valve changed last month and no problem since.

[theo575]

I'd say disconnect the battery again, but for a while this time - say 10 or 15 minutes.

Attach the battery again and this time let the car idle for 5 min.

Go for a drive and try to get on a highway, give it a bit of the beans WOT reving it up to 4-5k.

If this doesn't fix this issue then I'd clean the PCV valve.

Hopefully resetting the ECU again will get it fixed up.

[highlineMotors]

I had a similar problem on my 05. Had the purge solenoid valve changed last month and no problem since.

There you go. Start off with a purge solenoid valve. About $130 from the dealership i think. These units are common failures are Mazda 3's anyway. Sooner or later, you're going to have to replace it.

[vankiz]

I reseted ECU couple of times.. turned off battery for 40 mins.. pressed brakes to release left over life out of the car... then hooked it back up, turned on the car and idle it for 15 mins in P and another 10 mins in D gear.. nothing.

[vankiz]

There you go. Start off with a purge solenoid valve. About $130 from the dealership i think. These units are common failures are Mazda 3's anyway. Sooner or later, you're going to have to replace it.

Is it hard to get to to replace it? Is there a way to see if its done and needs a replacement?

[highlineMotors]

It's easy to replace. Depending on the model of the vehicle, you'll need a pair of pliers, maybe a 10 mm socket, wrench and extension. But they are fairly easy to replace. Just use some common sense. The unit is above the air filter hose, next to the battery. Don't know if you can tell if its done before. May need to check the history of the vehicle.

[mazdabetty]

Like I said before, it's normal. You car will NOT explode from idling at 500 RPM. If you want, you can always try re-filling your headlight fluid and try it while you point the vents down, but as you can see from the picture of my car, it is perfectly normal. :chuckle

(PS I know it's not QUITE 500 but my car was in park, it drops when it's just my foot on the brake. If it makes you feel better I can take a picture of that too).

http://img832.imageshack.us/img832/2748/photouaj.jpg

[vankiz]

Like I said before, it's normal. You car will NOT explode from idling at 500 RPM. If you want, you can always try re-filling your headlight fluid and try it while you point the vents down, but as you can see from the picture of my car, it is perfectly normal. :chuckle

(PS I know it's not QUITE 500 but my car was in park, it drops when it's just my foot on the brake. If it makes you feel better I can take a picture of that too).

haha you found my thread here too :P
yea it would make me feel better if you take a pic of that too :)

[cwp_sedan]

If you aren't getting any codes then it's probably not the purge valve solenoid. I definitely wouldn't replace that unless you are actually getting symptoms that point to the PVS, which you aren't.


Sounds more like a MAF or relearning issue but I've never had the car bog like that and I've pulled the neg connection all the time.

Does it bog and seem like it's going to stall? Chugging, etc? What does it do when you put it in neutral? Idle smooths out and RPMs go back up?

[vankiz]

Havent tried in neutral.. but when switching from D gear into park it smooths out back to 900..
also when pressing brakes in gear , after 2-3 seconds when RPMs drop, engine starts to be more quieter .. well obviously I guess since rpms drop.. but just a note.

[cwp_sedan]

Havent tried in neutral.. but when switching from D gear into park it smooths out back to 900..
also when pressing brakes in gear , after 2-3 seconds when RPMs drop, engine starts to be more quieter .. well obviously I guess since rpms drop.. but just a note.

To be honest, I don't think it's anything out of the norm.

Does the car bog and sound/feel like it's going to stall or are there just more vibrations? Idle is always around 750RM or so when it's warmed up.

Also are you stopped or driving or both when this occurs?

[vankiz]

To be honest, I don't think it's anything out of the norm.

Does the car bog and sound/feel like it's going to stall or are there just more vibrations? Idle is always around 750RM or so when it's warmed up.

Also are you stopped or driving or both when this occurs?
Maybe am overreacting.. it just stakked on me once on a red light, right after replugged battery kinda.. didnt let it idle much..
when driving all is norm.. slight vibrations on 110 km hour. normal idling when in P is 900.. when approach red light, let go of gas and brake, roll with 1000- 900.. applying brakes , and when completly stopped with holding brakes drops to 500

[mazdabetty]

http://img33.imageshack.us/img33/6321/photo2nhy.jpg

[vankiz]

thanks a lot mazdabetty! makes me feel better now!

[Prima Tech Aaron]

There is an updated pcm programing for the stall and low idle concern. you'd have to take it to the dealer to check if the computer in already up to date or not.
the other thing that usually helps is cleaning the throttle body.

[stock3]

Two words for this issue... Throttle Body.

Clean it and your problems will go away, I'm 95% certain of this.

[vankiz]

Two words for this issue... Throttle Body.

Clean it and your problems will go away, I'm 95% certain of this.

How can I find out if its dirty lol? I never seen a piece... is it difficult process? anyone know of a walktrhough maybe with pics?

[cSPEED]

If your car is stalling at stops it's likely your purge solenoid. It happened to me as well once I swapped it, it was fixed. The code I got was too lean at idle (don't remember the actual code). I'm selling a brand new PSV in the classifieds. If you'd like to check you are welcome to come by and use my DH to check the codes. Even try the PSV to see if it fixes it.

[stock3]

How can I find out if its dirty lol? I never seen a piece... is it difficult process? anyone know of a walktrhough maybe with pics?

You have to take off the intake tube that connects to the throttle body. then with the car off and a disconnected battery for added safety, you rotate the butterfly valve by hand to see the inside. It's most likely gunnked up with oil and carbon. You can simply use a rag, sprayed with throttle body cleaner to wipe off carbon built up from the edge of the valve a s well as throttle body walls that the valve seals against.
How do I know it?
A reverse of your situation happened to me. I cleaned the throttle body without resetting the ECU and my idle was about 900RPM in D when fully warmed up. It would also shoot up to 2.5k RPM on cold starts. After I reset the ECU my idle went back to normal.
Also a friend of mine at work had to change the battery in his Mazda 3 and his car was idling very low and stalled once or twice right after the change. I told him what happens to me and he got the throttle body cleaned at the dealer. His car was idling normally after that.

[vankiz]

thanks but im in ottawa.. far =\

[vankiz]

is it risky to clean it myself? hard to remove it? easily screw things up if done wrong?

[Wes08M3]

is it risky to clean it myself? hard to remove it? easily screw things up if done wrong?

Really hard to screw up. If its really gunked up you can use a toothbrush to scrub the TB.

Just make sure you wipe up all the crap before you put it back together. While you're at it, might as well clean the MAF too. Also very easy to do.

[Shadyslim]

Hey .... I need some feedback too.... Whenever I start my car , the rpm goes to 2000 for 5 seconds . Then it drops to 1500 for another 6 seconds while on neutral ... How come the rpm is moving when I'm in neutral ?

[Bosshammy]

i havent came into this problem with my mazda but my focus would do this sometimes it was automatic and turned out in the end for me it was the A/C compresser didnt have any lubricant in its system, so it was causeing the engine to use more power to operate causing the weird idle. something to check out just get a recharge kit from CT and get the lubricant its a seprate access port than the A/C gas

[Wes08M3]

Hey .... I need some feedback too.... Whenever I start my car , the rpm goes to 2000 for 5 seconds . Then it drops to 1500 for another 6 seconds while on neutral ... How come the rpm is moving when I'm in neutral ?

Is the engine cold when you start it? Like you're starting it in the morning for the first time of the day. If so, that's perfectly normal. The engine is idling higher to warm up the catalytic converter and will slowly drop down to normal idle speed as the engine warms up.

[trulankan]

so after seeing this post I checked my RPM gauge when idling at a traffic light and noticed that it does drop to around 600 RPM. The car has never stalled or anything. I have 2008 GT 2.3L with 5-spd auto. I guess this is normal then?

[vankiz]

so after seeing this post I checked my RPM gauge when idling at a traffic light and noticed that it does drop to around 600 RPM. The car has never stalled or anything. I have 2008 GT 2.3L with 5-spd auto. I guess this is normal then?

Yea I guess thats normal with 3's. My car hasnt stalled since.. I guess I didn't reset ECU properly last time, and didnt give it enough time to relearn, and drove it right away, so maybe thats why I stalled on the first red light.

If it hasn't stalled on you, you should be good then. Don't worry about it, unless something, and hopefully it won't, happen :P

[Wes08M3]

so after seeing this post I checked my RPM gauge when idling at a traffic light and noticed that it does drop to around 600 RPM. The car has never stalled or anything. I have 2008 GT 2.3L with 5-spd auto. I guess this is normal then?

Idle is usually 700-750 rpm and sub-idle as its called is generally around 600 rpm. Sub-idle is typical of newer vehicles with large amounts of electronic control.

You might notice, when your car has only been running for say 5 minutes and you stop at a light it will idle at 700-750 rpm but after your car has been running for 15+ minutes for example, and you stop at a light it will idle at 700-750 for a few seconds then drop into sub-idle at 600 or so rpm.

Next time you're driving, look for it. Mine does it, as did the other 3's I've had.

[vortexmazda]

Mine idles at 750-850 RPM when I stop at a light. After about 2-3 seconds, it drops to 500-600RPM. When I let go of the brakes, it will go back up to 750-850RPM.

[Wes08M3]

Sounds about right. Remember the tachometers are not doing to be deadly accurate. They don't put hash marks every 50 or even every 100 rpm. Most people just don't care to know the exact engine speed.

[trulankan]

i guess its done for better fuel efficiency? lower RPMs means less gas

[trulankan]

i wonder what a skyactiv would idle at

[Wes08M3]

i guess its done for better fuel efficiency? lower RPMs means less gas

Yes, it's done to improve fuel efficiency. The SkyActiv is probably the same since every internal combustion engine needs to operate at a reasonable speed to avoid stalling.

This is why they now have start/stop systems, to further improve on fuel efficiency.

[seek]

try clean the map and then dis and reconnect the battery. this should reset your idle speed

[Merlos]

I am having the same problem with my mazda3 2007. I change the alternator two day ago and I disconnect the battery, but after I did that the RPM goes low when I apply the breaks. Does anyone has any idea what it can be?.

[stock3]

I am having the same problem with my mazda3 2007. I change the alternator two day ago and I disconnect the battery, but after I did that the RPM goes low when I apply the breaks. Does anyone has any idea what it can be?.

Clean the throttle body and I'm 99% positive the problem will go away.

And to whoever said that 500RPM idle is set to save fuel, they are dead wrong. Mazda's idle RPM, as per service manual should be between 650-700 RPM (or something very close to that as I'm going of my memory here).

Any lower than that and the engine will be rough, shaking, and prone to stalling. That is why even big rig diesels idle around that speed despite their 3k RPM redline.