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Discussion Starter #1
Recently Ive noticed what appears to be a intermittent drop in RPM when idle.

Basically Im at a stop in neutral and I see and feel the RPM drop from normal idle speed to about 1/2 normal idle speed then it goes back up.

No CEL has ever come on at any point.

I never see anything like this when actually moving but it probably would be harder to tell.

Any clues what this might be? Am I getting a mis-fire of some sort?

Im not 100% positive but this may only be happening in the a.m. when I leave for work. Ill try and watch it today on the way home and see if it happens in the afternoon at all. (not sure if its related to engine warm up but only recently started and its not even cold here)

p.s. I do have an auto xray scanner so if that could show me something let me know and Ill check it out.
 

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I noticed somewhat similar behaviour. It would idle like a bag of crap (up-and-down between 500 and 1500 RPM), and then stall.

There was a TSB put out to re-flash the ECU, and it hasn't happened since.

What year is your '6?

It could also be water in your gas...
 

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Discussion Starter #3
Mine is 2005. It never stalls but it does drop Idle a few times when at a stoplight. Its also not a bunch of up/down idle. Its generally a drop then return to normal for a bit, then drop again etc.

From inside the car it feels alot like what happens when a/c compressor turns on and momentarily drops the idle before the car corrects it. However I dont have the A/C on so I doubt thats it.
 

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Discussion Starter #5
I have the CPE MafCi but I didnt take out any inserts so its just in the stock wheel well (minus resonator of course)
 

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Discussion Starter #7
Mine's always done that since the day I got it, with or without an intake.
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I havent noticed any drivability issues so far but it only recently started doing this. Hopefully Ill get some time to run it on the scanner this weekend (wednesday starts my weekend) and see if the computer is reporting anything wrong.
 

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I started a post on this about a month ago. I really started to notice this after I installed a CAI, but, the car has done it from day one. A lot of others have also experienced it. I've been riding in a 06 Pontiac G6 (v6) for the last 2 weeks with a friend of mine to work, this car is a rental and stock, and, it does it too. So I'm guessing the emissions control crap has something to do with it. I really wouldn't worry about it unless it throws a CEL or the car stalls.
 
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JTZako,

The reason it feels like you’re A/C is cycling is because it IS cylcing! Pop the hood and have a look while at idle and ANY heat/cool setting is selected with fan on.
I posted this on mazda6tech forum, and was told this was by design. Even if A/C or defrost is not selected, compressor will still cycle on any heat/cool settting. Does not make sense to me, but I bet that's what you are seeing although RPM drop should only be 100/150 RPM.
 

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Mine has done the same thing, without the a/c on - it's recently stopped, but didn't cause any driveability issues so I never said anything about it.
 

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Discussion Starter #11
JTZako,

The reason it feels like you’re A/C is cycling is because it IS cylcing! Pop the hood and have a look while at idle and ANY heat/cool setting is selected with fan on.
I posted this on mazda6tech forum, and was told this was by design. Even if A/C or defrost is not selected, compressor will still cycle on any heat/cool settting. Does not make sense to me, but I bet that's what you are seeing although RPM drop should only be 100/150 RPM.
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I have my whole air system completely off. The system is definitely not cycling. Plus, the Idle drops are not happening at the kind of intervals I'd see if the A/C was the issue. It can do multiple drops right together, or one drop in a span of 2 minutes at a light. Its pretty random.
 

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Discussion Starter #13
OK this is still happening. I finally got time to hook up the auto xray and run the car around to see if anything unusual appears. Unfortunatly since no CEL comes up I dont know what else I might be able to determine from the scan results.

The problem doesnt seem to happen until the car begins to warm up. i.e. when parked in my garage it took about 4-5 minutes running at idle before the idle drops started.

I checked my filter (CPE) and it looks fine, oil levels etc are also fine.

I did notice that when the idle drops like that I can hear the intake sound change. It almost sounds hollow compared to the normal sound. Its hard to describe and unfortunately I dont have a recorder to post a sound here.

I also sometimes hear a click, almost like the a/c compressor kind of click but the a/c system is powered off so I dont see how it could be coming from that.
 

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You know this recently started happening to me to, maybe just didn't feel it as I know have the stiffest CPE mount installed so I feel the drops it drops to say 600?

ANd driving home after seeing Dane Cook and on the way there I really opened her off on the way there and had a good time, but then inching throught traffic(MTX) I would scoot up a little and press in clutch and brake and the idle stayed at 1250 for a little then to 1000 then to reg idle, sometimes it stayed there for a bit, and not I notice it not smoothly returning to idle but like in smooth intermitnit stops.

This OONLY happens when the car is warmed up and been at idle for at least a little bit say a min or 2. I thought it was the Throttle Body motor?
 

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Discussion Starter #15
Ok so mine is still doing this and I've done more investigating...

I removed my CPE and MAFci. I created a "bypass" so I dont have to unwire the whole harness for the MAFci. I have the stock airbox back in the car.

I used electrical contact cleaner to clean the heck out of the MAF sensor.

The car still does this. Its not *quite* as noticable as it is with the CPE installed though but the RPM is dropping down to 500 or so and back up to 750-1000 when Idle.

A side note:

Im not sure if this is related but I've also been noticing that most of the time when I am accelerating from a stop or even going to 2nd or 3rd gear under acceleration I can feel an odd hesitation. Its as if there is a rapid fire gain/loss of power on the way up the RPM range before I shift.

Overall I think the problem may be getting worse because the idle drops are about 1 every 10 seconds when stopped at a light and the "hesitations" during acceleration is getting more noticable. Now that I have the CPE stuff out Ill probably take it to the dealer and see what they find.
 

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Discussion Starter #16
Took car to dealer today and left it with them. Got a call about them having trouble reproducing the problem. (of course the car only does it when it feels like it)
 

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I had the same problem and had to remove the CP-E since it amplified it. I now have an AEM and very rarely get it but when I do it's very subtle. I have tried everything to get to the bottom of the issue and haven't come up with any concrete answers. It hasn't occured in the last couple months so it's really a non-issue at this point. As a side note: when I had the CP-E on, my acceleration was never as smooth as it is now. There would be a slight 'dead spot' before the car really started moving. All in all it wasn't that bad but on some days it was more noticeable than others.
 

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It wouldnt be a fan comming on? When a fan comes on in the 6, I notice that they click, but is unoticable while driving. Taking power to start the fan(s) would cause a drop for a split second during idle until the fan started moving. Just a guess, I dont know to much about it.
 

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Running a cold air intake with the bumper insert cut out?
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I think you hit the nail on the head Stretch. That's what causes this problem for me. I tried taking the insert out of the bumper and after cruising at speed for a few minutes, I'd slow to a stop and the engine would hunt for the correct idle speed. I think it's a case of the ECU not understanding the variance in pressure. Fast moving air = low pressure, slow moving air = high pressure. I put the insert back in the bumper & went for a drive - the problem instantly went away. Took it back out and the problem came back again... So on and so forth. Removing this insert DEFINITELY causes a problem if you have a CAI. At least it did in my case.

I imagine this could also happen if you remove the plastic splash shields underneath.

Have those of you having this problem replaced the bumper inserts with mesh or something?
 
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