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I have a 2012 Mazda 6i, after about 20 Mike's it starts during and stalling. New spark plugs, new ecu, tcm has been checked, new maf, new alternator, the mechanics can't find the problem and I'm at a loss other than an exorcist. Any ideas?
 

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Find a better mechanic. Seriously. Should not be a big challenge. Battery voltage. Crank signal. Fuel pressure. Maf signal. Engine vacuum. There's a computer your tech should have that will stop you from throwing parts at it like it's the 90s and people don't know how to use a multimeter still lol.
 

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Oh shit damn. Ok so you're stating it does this after it has reached normal operation temperatures, right? You mentioned after about 20 minutes if I'm deciphering that correctly.

When your car is cold the ecu runs off of different parameters than when it's warm. Once it reaches a certain temp it reads the sensors differently than it would cold.

Idk how far your car knowledge goes, but open and closed loop essentially means your car will run on 2 different settings. One where it sees inputs and adjusts, and one where it just recycles inputs til you get to normal operating Temps.

My guess is it's something in that area. I'm flabbergasted that 2 dealerships (Mazda, right) could not find any issues what so ever.

What has been replaced so far? Any more insight would help us.
 

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Discussion Starter · #5 ·

Oh shit damn. Ok so you're stating it does this after it has reached normal operation temperatures, right? You mentioned after about 20 minutes if I'm deciphering that correctly.

When your car is cold the ecu runs off of different parameters than when it's warm. Once it reaches a certain temp it reads the sensors differently than it would cold.

Idk how far your car knowledge goes, but open and closed loop essentially means your car will run on 2 different settings. One where it sees inputs and adjusts, and one where it just recycles inputs til you get to normal operating Temps.

My guess is it's something in that area. I'm flabbergasted that 2 dealerships (Mazda, right) could not find any issues what so ever.

What has been replaced so far? Any more insight would help us.
As I said the cam position sensor the alternator the ECU the TCM O2 sensors battery
 

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About 20 miles into driving it starts stuttering then stalling. The rpms jump up and down.
Hi Rodney. I have something similar. Buy yourself an obd scan tool. Not expensive and it may give you a clue with fault codes what the cause is. Presumably this odd behavior of the engine is generating a check engine light? If you could narrow it to one cylinder that might make life easier. Possibly a wiring issue between the ecu and one of the injectors. There are lot of possible reasons. Getting some fault codes could possibly help unless its something like po300.
 

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Oh shit damn. Ok so you're stating it does this after it has reached normal operation temperatures, right? You mentioned after about 20 minutes if I'm deciphering that correctly.

When your car is cold the ecu runs off of different parameters than when it's warm. Once it reaches a certain temp it reads the sensors differently than it would cold.

Idk how far your car knowledge goes, but open and closed loop essentially means your car will run on 2 different settings. One where it sees inputs and adjusts, and one where it just recycles inputs til you get to normal operating Temps.

My guess is it's something in that area. I'm flabbergasted that 2 dealerships (Mazda, right) could not find any issues what so ever.

What has been replaced so far? Any more insight would help us.
Interesting I was not aware of this fact.
 

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I've gotten random misfire codes, the next thing I'm thinking is new coils, but I have several conflicting codes. I'm going to do a scan again today and see what it says now
The reason this is on interest to me is that I have something similar myself going on at the moment. The problem is that none of these parts is that cheap and by just swapping stuff you could be spending a lot of dough.
My car is ok but driving uphill starts the issues and the error codes will come on. mostly they are p0300, but yesterday I got s p0302, which I'm happier with. I got one new coil as a spare. That way I can test the car , if it produces a p0300, then I swap the coil into the next cyclinder etc. I like jack james comment on the reading different sensors once it has warmed up.
 

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Wiring loom. Thatll cause all of those.
 

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The clue seems to be that the car seems to run normal before normal operating temperature is reached when the engine runs on a higher fuel to air ratio. If there is an intake air leak, once the normal operating temp is reached, the air/fuel ratio gets too lean and the engine stumbles.
 
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