I have been battling this “project” for a while now, and i am at a point where i am going too need some help.
2010 Mazda CX-7 2.3 Turbo L3 – 6 spd Auto – NZ new
Vin : JM0ER…
202626 Km
Backstory; Towed in from 6 hrs away, has been to 4 other shops, obviously still not fixed, many hands and feet have been on this thing, many parts have been touched/swapped/cleaned/licked/adjusted/tested/replaced. many tests have been performed.
In the boot there are old OE sparkplugs, a low pressure fuelpump and a set of injectors.
There is a letter from the customer in the car, stating what has been done. Again, many, many things.
Why do we take this stuff on? Because we are (slightly) mad, a little obsessed and we like a challenge.
Process: Looked at live data and codes, OBD and OE.
2x codes; MAF and IAT, turns out MAF is disconnected.
Connect MAF and attempt to start engine, crank no start. It absolutely refuses to start unless the MAF is unplugged.
Disconnect MAF, it will eventually start and run like garbage, the car is undriveable.
When cold it will keep stalling, it will get (slightly) better when warm and idle by itself, at this point you can reconnect the MAF and it will no longer stall. I attached a little video of it idling and attempting to raise the engine rpm.
diag.net/file/f12lkgsmb…
EDIT: this is actually running with the LAF removed from the manifold, but still connected. I was testing for possible exhaust restrictions. With the LAF installed, it will still run like garbage, just not so loud…
It sorta feels like its missing as well, but its hard to be sure when it runs as garbage as this.
The scantools (Autel Ultra, Gscan2 and Forscan) are limited on this model it seems, there is very little in the way of bi-directional control. I can do an injector drop test, and that is about it. I do the drop test several times and i do not seem to get a response from cyl 2.
As the live data points out, LT always at 0%, ST jumps to 25% when it goes into C/L. LAF reads far too high (800 Ma), rear o2 stays at 0, FP sits at 1000 psi, injector p/w at 2-3 ms, Eq ratio at 1.3, intake manifold vacuum is not stable, engine load and MAF are all over the place.
Leave it running long enough and it will eventually log a P0171 Lean code.
So its running lean and it is adding fuel to compensate?
Cranking the engine, it sounds okay, but i started with a cranking compression test, RC vs Coil1 vs Exhaust pulse vs Intake pulse.
diag.net/file/f34ie23r1…
Don’t see anything weird there.
Next i spent some time scoping coils and injectors (current and voltage) Did not see any issues there either.
Cam/crank next, i thought i had my first issue there. Coil trigger vs Cam vs Crank.
diag.net/file/f6x3a0l5f…
every time it stalled, the cam sensor would always stop first. I thought i had a sensor issue, so checked powers and grounds to the sensor. (As i discovered, on this engine it seems the cam sensor is used for ignition control and the crank sensor for injector control. Disconnect the cam sensor and you get injector activation, but no ignition.)
I put a cam sensor in it, no difference. keep on going.
Cam vs Crank sensor correlation seems okay, compare to a few known goods.
i go in cylinder on no 1, and again, i do not see any obvious issues. 111 Psi running compression and 174 cranking, my valve timing seems okay, even though i do not have a known good (yet), but i have done enough of these now that i think i can spot an obvious anomaly.
diag.net/file/f6o12dks7…
Can i figure out why its missing? I scope 2ndary ignition next and i find a shorted sparkplug on cyl 2.
Pull the plug for inspection, incorrect plugs (offcourse), replace all 4 with new NGK’s and borescope all cylinders while we are there.
No obvious mechanical issues observed.
Take a fuel sample, nothing funny here either.
Pull both O2s and inspect Cat with borescope, perfect. Pull EGR valve and inspect, all good. Smoketest intake system, no leaks.
Disconnect all ports (purge,brake, etc) to intake manifold and block them, No change, still garbage.
Don’t like Maf readings, They seem too high, There is a test in the OE manual which states to check KOEO signal voltage. Test fails, New Denso MAF installed.
At this point i am running out of ideas. I scope each injector current, voltage and railpressure. All the injectors have good waveforms, each injector pressure drop seems the same. Scope the Spill valve, again seems normal.
I unplug the HPFP spill valve and the fp drops to around 65-70 psi. that seems okay too.
Attempt a capacitive discharge for ½ hr, no change.
disconnect the LAF, car will not go into C/L, Disconnect Map and it will go into C/L. Disconnect FRP, runs even worse (if that’s possible).
At this point i disconnected the FRP sensor and used a variable trimpot to dial back the FP to around 450-500 psi.
Success !!! Finally some progress.
diag.net/file/f305000s5…
All my numbers are finally back to normal, my o2s are functioning, my Eq ratio is acceptable, my idle is stable, engine load is good.
But (you might hear it in the video) the HPFP is squealing its head off…so now what?
i do not believe i have a faulty FRP, i am leaning towards a HPFP or the pressure relief valve on the rail.
Or i there something else i am missing?
A new HPFP is at least $600 cost and the rail requires some dissassembly to get to it.
Q: How do i prove that its one or the other? What test can i perform to determine which is at fault? I am trying to think through what a stuck open OR closed pressure valve would do and i am going in circles.
Theo.