Starts but doesn’t idle.

[Jayy_cee27]

Hey guys this is my first post, and I’m hoping I can get some insight. I’ve already done a lot of searching and can’t seem to find a solution, and I’m not sure if this is the right place but here it goes. I own a 2012 ms3 with about 86k. About a week and a half ago it was driving fine, I let it sit for a couple days, and when I went back to start, it would turn over but it’s not holding an idle. I’ve already checked for leaks and replaced the bpv hose. Checked my spark plugs and coil packs, replaced the battery. Replaced the camshaft position censor. Checked my maf sensor(seemed fine). Made sure I was getting fuel. Checked the throttle body. Did a compression test, from bank 1-4 it read 140,140,170,140 (which is in the green but someone said that those numbers might be low) haven’t done a wet compression test yet. As of right now I’m taking shots in the dark and not sure what else to do besides just having it towed to a shop and spending who knows what on shop fees. I’m hoping someone could give me a few solutions. Could this be a small issue that I’m overlooking or could there be an issue with the motor? I spoke to someone at a shop and he was telling me that I would need to do an engine rebuild, or at the minimum replace the head. Currently the car is a cork sport stage 2(turbo back exhaust with high flow cat, intake, hpfp internals, and an off the shelf tune from the Cobb accessport).

[danb]

what is your fuel pressure when you do a "key on-engine off" test? Have you checked the pressure relief valve?

[Vansquish]

Is it throwing any codes?

[Db09ms3]

Is the alternator charging?

[Jeff23spl]

i would investigate into fuel pressure and maf signal.

can you play with the throttle to keep it running by its own even if it isn,t ok to drive ?

compression is low but it need to be done while hot before diagnosing a rebuild need. . i won,t say it is perfect but you have plenty of compression to get it running ok. i dont think it is the first issue here.

Originally Posted by Db09ms3 Is the alternator charging?

it could ran for a while without the alternator

[Db09ms3]

My harness is fubar'd on my alternator so it runs for a few seconds then dies. Something to check.

[Jayy_cee27]

Originally Posted by danb what is your fuel pressure when you do a "key on-engine off" test? Have you checked the pressure relief valve?

Well we only checked to see if I was getting fuel and return fuel, we don’t have a way to check what the pressure is exactly. And I don’t believe we checked the pressure relief valve. Do you have a write up on how to check these?

Originally Posted by Vansquish Is it throwing any codes?

When we checked it was throwing p2088 p0113 and p0102

Originally Posted by Jeff23spl i would investigate into fuel pressure and maf signal.

Should I just change the maf sensor?

[MSMS3]

P2088 DTC

Check this link. Took me about 60 seconds to locate.

[Jeff23spl]

Originally Posted by Jayy_cee27 Well we only checked to see if I was getting fuel and return fuel, we don’t have a way to check what the pressure is exactly. And I don’t believe we checked the pressure relief valve. Do you have a write up on how to check these? When we checked it was throwing p2088 p0113 and p0102 Should I just change the maf sensor?

you likely not solve it without tools and without investigations. Replacing parts until it works is a long and costly process if you don,t have a spare donor just beside your door...

to check fuel pressure and everything else, you need an obd reader that support specific mazda pids like the high fuel pressure and some others.
a cheap elm327 with torque pro app and the mazdaspeed add on can do it for cheap or probably versatune free with an adapter and a pc computer.

same for the maf, most of the time it is a bad connection, a leak or even dirt on it. sometimes it can be the sensor itself but those car doesn,t seem to like aftermarket ones and it needs to be a turbocharged version. ms3,ms6,cx7-t

[Jeff23spl]

Originally Posted by Db09ms3 My harness is fubar'd on my alternator so it runs for a few seconds then dies. Something to check.

ok i see, but that harness also pick up the crank sensor and some more on the other side...

[Ms3Silver]

Sorry to revive a semi old thread. I'm having the same or similar issue. Engine starts but dies almost immediately. I've checked just about everything OP has in the post.

One thing that I've noticed from my AP is that in the ON position, I'm getting readings of 2000-2150psi. I'm thinking it's my RV not doing its job correctly, I'd just like some more opinions on that before I pull the trigger on a new one.