Eradicator

I was getting the check engine light and codes about misfires, so I just changed out the coils, spark plugs, and wires per a couple good DIY threads on this forum. Not long before that, I had the dealer change out an O2 sensor.

After changing out the coils and plugs, the car runs great except for at idle. Sometimes, but not every time, when I engage the clutch and brake to come to a stop, the car idles and drops the RPM well below 1000k. I have done some searching here and thought it might just take a few cycles for the computer to get the trim dialed in. After a few days and several drive cycles, it's still having this problem.

I inspected the air intake today, released the clamps on the hose between the intake and the air filter, and re-tightened everything. No change. I then tried the 20-brake-pedal computer reset. I needed gas anyway, so I went for a few miles drive to test it out. It didn't outright stall this time, but it still has the same behavior of bouncing down to around 500 rpm and back up to 1000-1200 when I idle and brake. A couple times, the batter light came on, but it didn't fully stall.

I have the Torque app and took some data using my bluetooth OBD Scan device. I'll attach a CSV with the data. I tried to select the appropriate parameters, but I'm new to this kind of thing, so let me know what else I should do. At first, I let it idle for >30 seconds. Then I stopped and restarted logging and did a 0-60 double-red-line. Again I stopped and restarted logging. I then did a stead-state at about 55 MPH / 3200 RPM for about 30 seconds, followed by another redline. Finally, I just re-enabled logging and let it run as I drove back home, hoping to catch it dip down to 500 RPM and maybe stall.

I appreciate any help troubleshooting. I'm hoping this last ECU reset will solve it, but I'm not sure after these past few days.

Eradicator

The zip file in the original post was using the free version of Torque. I ponied up the $5 for the full version and took some more log files.

This post has three new files with the full version of Torque:
1. Idle - Just sitting and idling
2. Red-Line - From 0-60 with two red-lines in first and second gear
3. Driving Stalls - Driving back home with part of the trip steady-state at 35 mph / 3500 rpm in 3rd gear, followed by a couple stalls as I had to stop.

I also noticed that the fan does not stay on to cool the engine after I shut it off, like it normally would.

Junkman 6394226

Probably a noob response... But Maybe try cleaning the MAF and change the oil? Had the same rev-bouncing symptom before I did that.

Easy_E1

iTrader: (2)

I would clean the MAF sensor. Don't know if you've changed your air filter lately either.
Have you looked under the car after driving? Checking to see if the Cat is red hot and glowing.
Depending how long you were driving with mis fire CEL's. Your cat can be clogged. Very common issue related to continuous misfires. This can cause stalling and loss of power.
Do you have any loss of power in the higher RPM range?

Eradicator

I looked at the cat yesterday after over a half hour or driving and it was noit glowing (not saying it isn't the problem).

I just pulled the MAF sensor and I noticed a couple things. First, it appears the plastic housing that partially protects the bulb has been broken off. I have no idea how this happened unless someone from Mazda was too rough with the air hose when doing something else. I attached a photo.

Secondly, when I reinstalled the sensor, both screws seemed to free spin instead of coming to a stop with some torque. I'm not sure if there is some fancy mechanism there, but it could also be that those threads somehow got stripped and it's not sealed. Yet when I gently pull on the MAF, it doesn't just slide out as if the screws weren't there.

Is there a recommended vendor for a replacement MAF sensor? Will I need a new air duct as well since it seems the housing threads are stripped?

Eradicator

I should also point out that it appears one of the leads on the bulb is breaking loose. I didn't pull on the lead at all to test it out of fear of further breaking it. You can see a little evidence of this in the pic I attached.

Easy_E1

iTrader: (2)

Looks like you need a new MAF sensor. I would say this is your problem. Make sure your MAF O-Ring is in good shape. No cuts or knicks.
Put some silicone on the threads of the maf screws and snug them in.
If that piece of plastic went through the engine it might have done some damage to an Apex seal. One never knows.
Don't know if you've done a compression test yet or not. But you might consider it.

Eradicator

Ok, after a trip to the parts store, I have a new MAF sensor installed. I used some hi-temp silicone to hopefully hold the screws in place. I installed it in the parking lot, reset the ECU using the brake stomping, and drove home (~10 miles). No stalls on the drive home, but a couple times where it was close (battery light came on). I'll give it a few drive cycles after letting the silicone set and see what happens.

I haven't done a compression test since the one about 15,000 miles ago, when it failed in one rotor and I got a new engine care of Mazda. I just realized today that when they swapped out the engine, they put back in the rusty old spark plugs that I removed recently. How cheap of them!

Eradicator

After a few more drives, it was still idling low and stalling. So today I checked the air filter. It wasn't all that bad (K&N), but I tapped it and cleaned it a bit with some compressed air. I then disconnected the battery for ~30 minutes to reset the KAM per This thread. Upon the first restart, it didn't stall, but the idle range was still questionable. I'll give it a few more starts/drives and see how this goes.

RedDream

You might want to check your battery's cables and make sure they are cleaned up nice and tightened properly not just on the terminals but everywhere you can tighten a bolt or screw. Also go to an autoparts store like oreillys or autozone and take your battery to them and have it checked as well as your alternator. You might want to try that. My car began acting this way and I replaced the battery and terminals sure enough I was on interstate 20 here in Texas when my battery light would flash and disappear..then pow!! Everything turned off and my steering wheel got hard... Yeah my alternator gave out while next to an 18 wheeler 😥

RedDream

Had your same symptoms even after cleaning my maf and filter.. Could be your alternator warning you it's having trouble keeping a charge

Eradicator

I stopped by a mechanic that changed out mt alternator and battery 3 years ago and asked him to check them again. He said he didn't have time until Monday (really? it should only take 10 minutes) but that he didn't think the battery or alternator could cause idle and stall issues.

So I went to Mazda and got a free oil change. During that, they tested the battery (but not the alternator) and it tested weak.

Then I went over to Sears Auto since my battery was just barely still under full warranty. The jerk at Sears wanted me to pay $20 to have him test my battery since he "couldn't trust anyone else's test results". I called BS, so he got his assistant manager. That jackhole acted like he was doing me a favor and waived the fee. They installed a new battery.

TL;DR - I now have a new battery and the stalling has stopped, although it's not completely fixed. I still have the low idle symptoms, where the dial bounces down around 500 rpm and back to around 700-800. This morning, after a 30-minute drive at highway speeds, I took it out of gear when reaching a stop light. The tach dropped to 500 or so and the battery light flickered. I really hope this is transient from the ECU "learning" the trim again, but I'm thinking there is some other underlying issue. Could it be gunk in the intake, valves, fuel injectors, ... ? Should I try some of that fuel additive that cleans the gunk or is that no-good for the apex seals?

I have an appointment on Monday morning with this mechanic, but he's not a rotary expert. I'm trying to decide if I should go to him or pay more for Mazda to diagnose.

Javii

iTrader: (1)

Hey, please do check your alternator. If it's bad it could be causing your battery to drain quicker and eventually weaken it.

Also:

-Clean the ESS sensor if you haven't
-Clean the Throttle actuator, I had issues with stalling for weeks until I got a CEL for the actuator stuck closed. You could have oil in there from overfilling the engine.

Eradicator

I'll go to Autozone and get the alternator checked soon.

I found a good pic of the ESS sensor here, but I'm not sure how to reach it. Do I have to remove the air box? I'd rather not considering how delicate that MAF sensor is.

I couldn't find any obvious DIY threads for the throttle actuator. Can you point me to one?

Javii

iTrader: (1)

To clean the Throttle actuator valve it's best if you remove the throttle body itself and clean it from both sides.

It's pretty simple:
Remove the airbox, the intake tube, and all the hoses attached to it. Remove the coolant hoses that attach to the throttle body and remove the throttle body, then you can use a degreaser and clean it. Still, leave this for last if you find it confusing, as it probably isn't your issue.

To clean the ESS I didn't have to remove much because I have a CAI so no airbox in the way. I'm not sure how much the box actually blocks it, but if you can find a way to spray it with a degreaser and use a paper towel to clean it it'll help a lot, you don't even have to remove the ESS sensor itself. You should be able to reach it from under the car as well.

Eradicator

The alternator tested out okay.

Any opinion on the gas additive cleaner stuff?

djfa

iTrader: (3)

Hey man,

I had the same problem as you. Unstable idles, the engine was running fine but the rpms never wanted to stay stable and the car would jerk around. Myself, i had changed plugs coils wires, nea air filter, clean maf and reset fuel trims. My cat was also fairly new from the dealer. I took it to the dealer and just asked for a compression test. Turns out my engine was bad. All it takes is a 120$ at the dealer and you will know for sure.

You could also have a vaccuum leak somewhere? Check your pipes make sure everything is nice and tight. Maybe your wires arent tightly secured on either the coils or plugs?

Eradicator

It's been about 2 weeks since changing the battery. Since then, the stalls have stopped. Within a couple days, the idle trimmed out, and now it seems back to normal. Strange. I would think with the alternator going, the battery wouldn't be so key in a running engine. Other than an occasional vibration at idle, I think the case is closed. For the vibration, I think it's time to replace the motor mount (the one that wasn't designed properly for the heat).