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I'm trying to help my grandson w/a problem on his Mazda 6 2.3 NA w/97,000 miles. I've been wrenching for about 35 years, mostly Toyota and VWs, so I'm a NOOB when it comes to Mazdas.

This has been an on-going intermittent problem. Car will just die, sometimes it will restart immediately other times it sits overnight and then it restarts.

I finally got it to happen for me. There is no spark. There originally was a code indicating that the bank 1, sensor 2 O2 was bad. Replaced it, cleared code and car ran good for about 10 miles and it died. Died dead, no warning, no miss and NO CODE! It just stopped. Got the car home and found there was no spark at 1, 2 and 3. Didn't bother checking 4 at that point. Waited about 15 minutes and it restarted. Let it idle and after about 10 minutes it died again. Verified no spark again.

So, it seems to be something associated w/spark. Crank sensor or cam sensor, but why does it restart if I let it sit long enough. I've read that it could be a ground fault on a reference signal to the computer.

The wierd thing it that it seems fine about 10 minutes or so before it dies. So, I was thinking a faulty temp sensor or heat/expansion causing a short.

I have a Haynes on order, but looking to the people on this forum for insite. Any help would be greatly appreciated.
 

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The wierd thing it that it seems fine about 10 minutes or so before it dies. So, I was thinking a faulty temp sensor or heat/expansion causing a short.
I think you nailed it there; its heat related either induced from the engine or the passage of current.

Lets rule out what its isn't.
The engine is still heat soaked after 10 minutes if sitting - i.e. its likely hotter than when it shut off. So - things like:
Coil packs = no
Fuel pump = no
Temp sensor = no
Battery, charging system = no
O2 sensors = no

Think of it this way; how many things can be off line and still allow it to run in limp mode. All of the Limp mode inputs could be DEAD and not cause this, i.e. air/water temp sensors, MAF would set a code, all the EGR stuff = negative. . .

Although I don't own a I4, I'd be suspect of what ever interfaces between the ECM and the ignition source. Yes, the crank trigger would be in this bucket and if the I4 has an ignition module between the ECM and coil(s), Id be looking close at it!

Find a schematic of inputs and outputs that will stop the show and look at which of them could be the weakest link regarding temperature. Sorry I'm out of time or I'd dig in further. . . I will check back tho!
 

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So, should I just go ahead and replace the crankshaft and cam sensors? It's about 25.00 for each of them. I could try and test the voltage and resistance of his current sensors, but it would be just as easy to replace them at this point.
 

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Me personally I've never liked throwing money at things when I'm uncertain as the results can vary so much. Hidden in the manual may be a way to test them but this could be painful and slow going doing before and after (when its failed) readings.

If you have money to burn, it is an option, but before I go that route I'd by two big cans of electronics "Freeze Spray" and get it hot and to fail and blast no more than two things at a time. Hit the key and test it. Remember, this may not be Engine Heat related as a hot engine does not Cool in 10 minutes. But feeling for HOT parts when the engine is cold started may be helpful too. <Throwing out ideas.

Have you searched for other posts like this?
 

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I've searched and searched, but everybody seems to have a completely dead issue. Nobody has the same problem, where it will restart after being left to sit. I do like your freeze idea. I work in the IS/IT industry, so I can get a couple of can pretty easily.
 

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Short Update

We seem to be able to recreate the problem on demand now. Started the car this morning and let it idle for 10-15 min and it died. Let it sit for a few minutes and restarted it. This time it idled for about 1 minute and died again. I'm going to pick up a couple of cans of C02 that we use to clean computers. And see if we can eliminate sensors as the possible cause. Will prolly update you over the coming weekend.
 

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Extremely old thread i know, however i have a Mazda 3 sport (2006) exhibiting all the exact same symptoms - so did this ever get resolved? we've tried changing the Crank sensor and even swapped the entire ECU, Body control module, dash clocks and ignition barrel / transponder as we assumed it must be ECU related as absolutely no DTC's / codes came up when scanned. Total mystery and makes the car totally unusable! any thoughts? thanks
 

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Quote, I finally got it to happen for me. There is no spark.
Not really a solution but an area that may need examination.
Good luck,hope you get it sorted.
 
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