okay so i'm at a complete loss i have an amazing 2016 with 200,000 km on it, i recieved it as money owed for work performed on a different vehicle. at the time it was a no start. tracked down a failed low pressure fuel pump, okay replaced the pump and now it starts and runs amazing but only until you shut it off and go to restart it, when it is hot it will NOT start. it tries to start it almost starts but it wont. press down the accelerator and it tries a little hard then has a bit of a hard time turning over until you let off accelerator and it does an almost start
wait for it to cool off and boom it starts and runs amazing, try a little starting fluid and it makes 0 difference, check to make sure spark is there its good, fuel is good, compression is excellent but ok why wont it start when its hot, replace cam and crank sensors, spark plugs and no difference.
break out the scan tool and watch live data and the only thing i can find out of wack is the exhaust cam timing actual vs desired. when cold they are very close to eachother within a couple degrees. matches the intake desired/actual differences however as the engine warms up and gets hotter the difference between exhaust cam actual and desired starts to get further and further apart. and exhaust cam actual just seems to be completely random and all over the map however no codes. ONE time early in diag when battery was low i got a cam/crank corelation code but since that one time zero codes what so ever. if anyone has any idea that please let me i

 

Welcome to the forum

 

To start with if your engine does not start there will be a DC (S). There are 3 area's to look when you scan your ECU using a directly connected Diagnostic scanner.
Otherwise you have either a failing ECU, or harness to the ECU is not making good connectability.

 

As Callisto said read all your codes.
My guess would be at those miles a worn/stretched timing chain. Which can result in error codes from cold (tighter chain) to hot (relaxed chain).
Which can also cause starting and running issues.

 

Could be vapor lock. That's unusual on modern engines, but still worth checking all fuel hoses/lines and making sure they are in good condition and not touching any hot metal parts.

 

It always something to check . However the cause leading up to that would have had a few TC and the check engine light would have been shing on your dash.

Look at the I/M monitors from the responses you will have more than one not emission ready which will also indicate you should find DTC(s) at least in the permenate file of the ECU if not the pending. If none of these then you have a communication issue with your ECU or a problem with the ECU

 

like i said before, one time it came up with a crank cam corelation code but otherwise nothing and that is weather i check with a scantool or a generic OBD, all readiness monitors have completed acccording to what i'm seeing and the only thing i see is the exhaust cam actual is all over the damn place when desired is very fluid, goes up and down depending on load. however now that i think about it the scantool i have will not let me do any "special functions" for some reason. it is greyed out. i'll try another scan tool tomorrow but there should be some special functions at least right?

 

Debating this with me is counter productive to helping you.
Ok so just saying this is not how an ECU works.
There is not a OBDII or CANbus control system I can't find the cause of the target area in an hour or less. You have a communication concern with your ECU. What you have said from the first post you should have multiple DTCs and your monitors will show in fault. The target area is the ECU.

ASE



Good luck with your Mazda

 

Just a thought, I had a very similar issue and it turned out to be the main fuse relay. Was a mission with plenty of choice words.
My 2 cents only.

 

You would have had a DTC (s) to help u find the issue (main fuse relay)