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Old 11-29-12, 17:47   #1 (permalink)
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Join Date: Sep 2012
Location: Little Rock, AR, USA
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intermittent loping idle?

sometimes my car idles roughly. usually after it's warmed up to operating temperature. when i first start it in the morning it idles at 1000+ and then will idle normally at 600 or so but after a while, and not always, the rpms will dip to 500 or so and it will start running roughly.


if i even tap the gas it will smooth right out and then rev back down to 500 and resume idling roughly.


its a head scratcher...any ideas? egr? pcv?

93 MX6 I4 MTX
bone stock...but not for long.
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Old 11-30-12, 8:54   #2 (permalink)
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My guess would be Idle Air Control (it's low down on the throttle body). Maybe it needs to be cleaned. But that's just a guess.
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Old 11-30-12, 21:52   #3 (permalink)
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is it located by the egr? i can use brakleen to clean both of them?

93 MX6 I4 MTX
bone stock...but not for long.
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Old 12-1-12, 18:07   #4 (permalink)
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Check for good spark on all the plugs, cap and rotor. Check coolant level. Check for air leaks especially around throttle body gasket. I have a youtube video on cleaning the IAC for the FS engine.


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Old 12-1-12, 23:27   #5 (permalink)
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thanks for the reply, man. i'll be checking that stuff tomorrow.

the spark plugs are new...no clue about the rest of it. that IAC looked like a biatch tho.

i've seen some of your other vids and have commented you on youtube before. keep making them becuase there is just not enough mx6 reference vids out there.

thanks again.

93 MX6 I4 MTX
bone stock...but not for long.
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Old 12-2-12, 14:00   #6 (permalink)
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The hardest part is getting the damn thing off. After that it's a breeze. Replace the IAC screws with hex bolts so in the future it will be much easier if you ever want to check it again. Just FYI if you unplug the MAF harness make sure to reset the ECU before plugging it back in.

Thanks for the compliment. I've got a lot more videos coming this year with the ATX to MTX swap and other little projects.

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Old 12-6-12, 15:38   #7 (permalink)
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Getting those Phillips heads off isn't too bad with a manual impact. I've had the same problem for a very long time. Replaced or cleaned just about everything (disty, plugs, wires, egr valve, Iac cleaned, throttle body cleaned, new intake boot, all hoses.....) and still have hit it. Love to hear what you find if you solve the problem. Good luck.

Last edited by Enigmacar; 12-6-12 at 15:43..
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Old 12-7-12, 19:06   #8 (permalink)
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When someone says that it idles fine until the car warms up my first thought is always the O2 sensor. During closed loop operation the ECU runs in a programmed preset operation (open loop). When the car warms up it enters closed loop and then all the sensors start feeding it live data and the ECU runs off of that live data.

Idle issues can also be caused by the thermostat opening after the car warms up and thermostat opens. If you have a coolant leak you can get fluctuating idle so make sure you coolant level is correct.

Other than that make sure you aren't getting any kind of spark loss from the plugs or wires. Look for good blue spark. A $5 spark tester from any auto parts store is excellent for that.

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Old 12-8-12, 13:21   #9 (permalink)
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thanks for the replies!

i found a broken vacuum hose that looks like it belongs to the EGR BOOST SENSOR VALVE(passenger side of Intake Manifold, lower of 2 similar looking fixtures...orange plug)

i plugged the holes with my fingers while the car was idling roughly and noticed no change. there is no vacuum present in the hose nor the valve itself.


this could def be causing this problem, right? how do i remove this valve? i have the shop manual but dont see any specific instructions on removal.

i'm uploading pictures now.

93 MX6 I4 MTX
bone stock...but not for long.
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Old 12-8-12, 13:26   #10 (permalink)
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[IMG][/IMG]



[IMG][/IMG]


its the vacuum hose with the orange stripes on it that does not connect to anything...not sure if that means anything to anyone. and the wire harness plug for the valve in question is orange.

i'm going to autozone to have them plug in the code reader.

Last edited by ohnoitsthatguy; 12-8-12 at 17:33..

93 MX6 I4 MTX
bone stock...but not for long.
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Old 12-9-12, 11:50   #11 (permalink)
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aaaand i just SNAPPED the connector that my yelllow vacuum line connects to the solenoid above the orange one!

now i have 2 busted solenoids!!!11 i couldnt even get them off of their bracket.

this sucks.

93 MX6 I4 MTX
bone stock...but not for long.
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Old 12-9-12, 12:19   #12 (permalink)
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will this egr vacuum solenoid work on my I4?

Mazda EGR Vacuum Switch Solenoid Valve K5T49090 FS05 | eBay

93 MX6 I4 MTX
bone stock...but not for long.
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Old 12-9-12, 15:42   #13 (permalink)
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All of the solenoids work the same on the I4. When fed 12v they open. They are grounded all the time. It's a pull down solenoid. It will work but you might have to hard wire it if the connectors aren't the same. I would just go to a junkyard and find another solenoid. I have a video on testing both the vent and vacuum solenoids on the I4. As for what you can do with the snapped off vacuum tube (assuming the one on the back of the manifold) you can try JB weld (limited success but has been done) or drill and tap a plumbing style fitting.

Oh and another thing just for future reference. Never try to pull off the hose from the back of the intake manifold it will snap. You must first slice it with an Xacto knife and then peel the hose off like a banana. As dumb as it sounds (blame Mazda) the vacuum port plugged into the back of the huge aluminum intake manifold is actually plastic and will snap with minimal force. Unfortunately sounds like you've found out the hard way.

Here are some videos that might help. Solenoids used on the 626 I4 are exactly the same as the MX-6 I4.




Last edited by djdevon3; 12-9-12 at 15:50..

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Old 12-9-12, 20:05   #14 (permalink)
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alright cool. i bought that ebay solenoid...the connectors appear to be the same but i can splice something up if i need to.

i have read the shop manual procedures for testing these and will be doing that before installation.

thanks again for the info!

93 MX6 I4 MTX
bone stock...but not for long.
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Old 12-10-12, 0:10   #15 (permalink)
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Quote:
Originally Posted by djdevon3 View Post
when someone says that it idles fine until the car warms up my first thought is always the o2 sensor. During closed loop operation the ecu runs in a programmed preset operation (open loop). When the car warms up it enters closed loop and then all the sensors start feeding it live data and the ecu runs off of that live data.

Idle issues can also be caused by the thermostat opening after the car warms up and thermostat opens. If you have a coolant leak you can get fluctuating idle so make sure you coolant level is correct.

Other than that make sure you aren't getting any kind of spark loss from the plugs or wires. Look for good blue spark. A $5 spark tester from any auto parts store is excellent for that.


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93 MX6 I4 MTX
bone stock...but not for long.
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