Weird idle hunting 06 mazda3 2.0

[Smogsucks]

Its also possible he had more then one issue to begin with. One covering the other. I'm sure you've come across this in your experience.

Did the OP get his alternator from a wreckers? I don't recall him saying so, or I missed it completely. If so then the probability of a faulty alternator goes way up.

The reason I mentioned the ground cables is because of his comment much earlier about his lights dimming with his system use during high output. My system is equivalent in power numbers and I've never had dimming occur. He should probably check ALL grounds throughout to eliminate that as an issue is what I was getting at.

_3

As for sound system, I completely disconnected it from everything, as that was my first thought. During troubleshooting, I disconnected ALL wires going to anything sound system related, to try and isolate where the issue was. Nothing changed.

[Smogsucks]

Also, wierd bit here, (as if this whole damn thing isn't already weird) sometimes, more often than not, my car will shock me as I'm getting out of it if I am touching the body of the vehicle. Could be nothing, or could be everything. Isn't there a body ground somewhere?

[Smogsucks]

https://youtu.be/5Pl1eIhJGhc
Video with cycle of headlights on and off.

[Smogsucks]

Alternators could come defective but unlikely since they are supposedly tested.

Try simple things first like;

Check the alternator output close to the source.

Check that your ground cables are all good, not frayed, loose or corroded. Even add another cable if you have some large gauge wiring hanging around.

Check your battery is fully charged also, the whole episode could have drained it considerably putting a huge strain on the alt, which would require quite a drive to charge it up.

Btw, your video doesn't show what happens when you put a load on either.


_3

Okay so took a voltmeter and tested for resistance on the ground circuit and positive lead to battery, both well below a tenth of a volt. Fluctuations happen at alternator as well same readings. Had both alts tested on a bench, old one passed with flying colors no ac current leak, diodes were fine regulator is functioning. Same with new one. One thing I learned. The pcm has some say as to voltage regulation based on current driving and load conditions. There was a service bulletin for the a/c causing this same issue, and it recommends a firmware reflashing. That's about all I could find though.

[morganc]

That shock is is simply built up static charge that you get from normal driving. The car, being on rubber tires, is completely isolated from an earth ground so you become the conductor for any built up static when you exit the car. Nothing to do with the 12V system. If the alternator is testing out ok, then I'd start to veer away from electrical and start thinking of things like fuel pressure and EGR.

Also, wierd bit here, (as if this whole damn thing isn't already weird) sometimes, more often than not, my car will shock me as I'm getting out of it if I am touching the body of the vehicle. Could be nothing, or could be everything. Isn't there a body ground somewhere?

[Smogsucks]

That shock is is simply built up static charge that you get from normal driving. The car, being on rubber tires, is completely isolated from an earth ground so you become the conductor for any built up static when you exit the car. Nothing to do with the 12V system. If the alternator is testing out ok, then I'd start to veer away from electrical and start thinking of things like fuel pressure and EGR.

Yeah I'd buy that if it wasn't for the ridiculous voltage fluctuations. There is no way that engine hunting by itself is causing THAT much fluctuation in the voltage. Unless I'm completely wrong there? And engine hunt from 650 to a 1000 max, very rarely dropping below 650, the hunt almost always happens UPWARDS of normal idle, forgive me for that not making sense. Then again I am thouroughly convinced that electricity is some form of witchcraft. So, how would I go about checking fuel pressure while the is happening? Checking fuel pressure any other time would most likely just yeild normal results and totally deafeat the purpose. As for the egr, it works just fine, and has been cleaned. I have (finally) gotten a mil code. P0421 warm catalyst bank 1 efficiency below threshold. Guess the precat is starting to go.

[Flagrum_3]

I would still think its electrical. Changing voltages under different loads doesn't, to me anyway, point to fuel or egr related problem. But I could be wrong.

You sure your battery is at 100%?

If all is well with your battery, alternator and grounds I would suspect possibly a firmware issue or maybe even a sensor.

_3

[Smogsucks]

This is what I was thinking. I know of a service bulletin that dealt with the a/c causing this and the fix was a pcm reflash. It's a similar enough problem that it might work. You mentioned sensors. Any ideas there?

[Smogsucks]

Yeah battery is 2 years old, tested fine, cca were right where they are supposed to be and I've never had an issue with it.

[McGuyver_3]

Yeah I'd buy that if it wasn't for the ridiculous voltage fluctuations. There is no way that engine hunting by itself is causing THAT much fluctuation in the voltage. Unless I'm completely wrong there? And engine hunt from 650 to a 1000 max, very rarely dropping below 650, the hunt almost always happens UPWARDS of normal idle, forgive me for that not making sense. Then again I am thouroughly convinced that electricity is some form of witchcraft. So, how would I go about checking fuel pressure while the is happening? Checking fuel pressure any other time would most likely just yeild normal results and totally deafeat the purpose. As for the egr, it works just fine, and has been cleaned. I have (finally) gotten a mil code. P0421 warm catalyst bank 1 efficiency below threshold. Guess the precat is starting to go.

Checking fuel pressure you would need a gauge between the fuel feed line and the fuel rail. Unless you have a Schrader valve on the fuel rail which I don't think the 3's have. Seeing how easy it is to duplicate, you should be able to catch it really easy with the gauge hooked up. I doubt the 02 would cause the crazy surging, I'd be more convinced about a misfire and higher fuel consumption. I've had a mazda 3 2.3 a long time ago that ran like a bag of crap with no codes or anything and long story short turned out it was a bad mass air flow sensor. Didn't have surging/power fluctuations. The only reason I wouldn't think the PCM flash will help is because the problem is able to be duplicated with many different load options than just the AC. Unless, every individual load is replicating the AC operation.

[morganc]

Yeah, you'd have to install a Tee in the fuel line with the special push on fuel fittings (available at most auto parts stores). I'd do what a poster below experienced; hook up a second running car like you're boosting the battery. You'll have an additional electrical system stabilizing your car's electrical system. Measure voltage while this is happening and if the car is still hunting while voltage remains reasonably stable, then you can cross off electrical from your culprits.

[McGuyver_3]

I'm wondering if you may have a bad connection (broken wire) between PCM-ALT or a bad PCM all together. Now knowing that the alternators pass with flying colours, you would have to find out what the signal line from alternator to PCM is supposed to see and or do. On cars at my work they are can-bus lines and operate at certain voltage/pulses. If the PCM is not outputting the proper or stable voltage, then that may be an issue as well.

[Smogsucks]

I'm wondering if you may have a bad connection (broken wire) between PCM-ALT or a bad PCM all together. Now knowing that the alternators pass with flying colours, you would have to find out what the signal line from alternator to PCM is supposed to see and or do. On cars at my work they are can-bus lines and operate at certain voltage/pulses. If the PCM is not outputting the proper or stable voltage, then that may be an issue as well.

ill see about getting a diagram. i have access to alldata, so ill start there. on tuesday, im getting a reflash done from mazda, ill also see if they can check whats going on in in their little black box they allow nobody to have the software to. as for fuel pressure, not sure, havent done it yet but, i can tell you that the ignition advance bounces around like crazy, anywhere from +20 to -10 degrees when its doing its thing. commanded air fuel ratio is pretty steady, always about 14.75 no matter what the engine is doing. maf readings are fine, as is manifold pressure, 2.5 g/s and 4 psi respectively, does not correlate to hunting at all. (using torque app, with wired otg on my phone). unfortunately fuel rail and fuel pressure isnt supported on mazdas... so going to do that analougue when i get a suitable gauge. something i noticed tonight... when heater is on there is this kinda loud clicking noise every 10 seconds or so, like a solenoid, but much louder, that corresponds with a dip in rpm and then a surge, rinse and repeat. formerly this only happened with the a/c. also, the hunting has become... inconsistent. sometimes it will do it, sometimes it wont, with the headlights.

[Smogsucks]

Checking fuel pressure you would need a gauge between the fuel feed line and the fuel rail. Unless you have a Schrader valve on the fuel rail which I don't think the 3's have. Seeing how easy it is to duplicate, you should be able to catch it really easy with the gauge hooked up. I doubt the 02 would cause the crazy surging, I'd be more convinced about a misfire and higher fuel consumption. I've had a mazda 3 2.3 a long time ago that ran like a bag of crap with no codes or anything and long story short turned out it was a bad mass air flow sensor. Didn't have surging/power fluctuations. The only reason I wouldn't think the PCM flash will help is because the problem is able to be duplicated with many different load options than just the AC. Unless, every individual load is replicating the AC operation.

as for misfire, misfire count on all cylinders in the last 300 miles(last time i disconnected the battery) is in order of cylinder 1-4, 3,5,2 and 1. so doubt its that. maf also reading proper voltages and readings.

[Smogsucks]

I'm wondering if you may have a bad connection (broken wire) between PCM-ALT or a bad PCM all together. Now knowing that the alternators pass with flying colours, you would have to find out what the signal line from alternator to PCM is supposed to see and or do. On cars at my work they are can-bus lines and operate at certain voltage/pulses. If the PCM is not outputting the proper or stable voltage, then that may be an issue as well.

Ok so took it to Mazda. Turns out there is a problem with fuel, when it stalls, the pressure immediately goes to zero, it supposed retain pressure for about five minutes Utes. Also known problem with intake manifold gaskets is the little tab on them interferes with the seal at times, so they told me to cut that tab off. So I'll be doing that, and there's a possibility that the fuel pump is bad

[Smogsucks]

I'm wondering if you may have a bad connection (broken wire) between PCM-ALT or a bad PCM all together. Now knowing that the alternators pass with flying colours, you would have to find out what the signal line from alternator to PCM is supposed to see and or do. On cars at my work they are can-bus lines and operate at certain voltage/pulses. If the PCM is not outputting the proper or stable voltage, then that may be an issue as well.

The only weird thing the pcm is doing is sending more fuel than usual probably because the gasket on number 2 cylinders intake port is leaking, for the aforementioned issue with the tab