engine stall, please help...

Hi, i have a problem with my cx-7
it don't start at all, it cranks normal, start for 1 or 2 seconds, then stall...
if i unplug maf sensor, it is starting but idle raise UP and down, and afr is 20-22... :-( stft AT 0
if i turn it off, plug black the maf, and restart, sometimes, it runs, but impossible to rev, afr at 20-22 and stft at +25..
when running without maf sensor, there is missfire, rough idle, and vacuum is Bad... -0.1 to -0.3 bars, normale it was -0.8 bars at idle.
if is rev it near 3000rps, then the vacuum goes black to -0.6 bars -0.7 bars, and then the motor run good, afr goes to 15, and no more missfire...
so i thought about vacuum leak? but Nevers found any.. AT idle with pressure and smoke machine, and also soapy water, also sprayed brake cleaner everywhere.. no reaction...
if i spray a little brake cleaner in the intake, the car run fine a few seconds..
i also notice that when i am a 3000rpm with afr good (15) , if i try to give gas, it revs good, but there is not a lot of boost, it raise to 0.4 0.6 bars, instead of 1.3, but i know that in neutral Gear, it never built boost like when rolling... (sorry for the pressure in bars, i'm from France.. but there is not a lot of 2.3 disi here ..son i try to ask to the best Mazda owners... i do my best to write not too Bad...)
i replaced maf, Map, inkake manifold gasket, throttle body gasket, all clamps on intake hoses including the turbo ourlet one..
checked all hoses... replaced pcv valve, i'm on it for 3 month... i'm going mad...
do you have any Idea?
i thought about buying a set off Cooper injector seals... corksport
but could that be an injector seals problem? that is leaking and throwing air into the cylinder,. i'm not sure, because when i throw brake cleaner on the injectors, it dont make the idle better or reving..
if you Can please help me...
best regards..
al

 

Do you have a method of logging any data? An Accessport, or Versatune perhaps?

edit: without diagnosing the issue you are just throwing money away.

 

Forscan is free and will allow you to data log any PIDs you want as well as read DTCs and take snapshots of events that trigger DTCs.

https://forscan.org/home.html

Just need a compatible ELM Bluetooth adapter which is fairly cheap.

As jsmith said you need to try and pinpoint the issue before you spend any more money on parts.

 

hi, thank you, i will try to make a log,
i have no DTC or light on dashboard..
non stored code, only maf when i start thé car without.
the only Bad things are vacuum pressure that goes too high and that make engine stall, and stft at +25 when the car wants to start with maf plugged. when maf unplugged, stft is AT 0.

 

Bonjour al,

I'm not convinced this is the issue but worth checking fueling as well. Out of curiosity what's your hpfp pressure reading at key on engine off (koeo), idle and 3k rpm. Also PRV test

There is also a very small ground near the hpfp that can cause many issues ensure it is clean and German torqued

Bon chance

 

thank you, i will look tomorrow, but if i remember.. i have near 25 psi when off, 480 at idle (without maf sensor .. ) 1400-1500 a 3000 RPM stable, and 1900 when wot ( in neutral Gear... ) i have autotech hpfp internats, when it was normal, it can go to 2100..
the ground near hpfp was checked..
the strange thing is why it missfire with Bad vacuum and afr at 22 in low RPM, and when i pass 3000rpm, and keeping revs at 3000 the vacuum goes black to normal values, it stop missfire and have good afr...
it looks like a Big vacuum leak... but can't find anyrhing...
that's why i asked about lthe seals under injectors... if it's possible that enough air that cause lean mixture is coming in from here..

 

If it was an individual (or even multiple) cylinders wouldn't you be able to see that on the spark plugs?

The high pressure relief valve test Awa mentions is to get engine warm, then turn off engine and watch the high pressure fuel pump variable. It should rise to over 1600 PSI (or whatever in bar) I belive. In a minute or two. If not it's a bad valve.

 

hi , everybody..
so i have checked fuel values:
ican't start the car with maf sensor plugged..
* engine off: 40 psi (non crank for 2 days)
* idle warmup: 1400-1600 psi ( with maf unplugged ) vacuum -0.4bars - afr 22
* idle motor hot: ( motor shaking, nearly stalling ) 1000psi - vacuum -0,2 - - 0,3 bars- Map 64kpa - afr 23
* 3000 RPM stable: ( motor run good ) 1350 psi - vacuum -0.7bars - Map 33kpa - afr 13.9
*Key off: 1100 psi,
*1 minute after: 1300 psi
*2 minutes After: 1500 psi
*3-4 minutes After: 1820 psi
then it goes vert slowly down..
i Hope that will be useful to you

 

hi,
i have replaced injector seals, just to be sure that air was not entering here, i put some corksport Cooper seals, and i'm still having the same issue..
afr 22, stft +25, and car dont start... it cranks... it run 1 second, then rpm goes nearly 0, then it revs to 1500 RPM half a second then it stalls...
vacum is at -0.1 to -0.3 bars instead of -0.8 bars as it was before..
could a stick open egr do that?
if you didn't read previous post, i had a fuel leak from injectors, i replaced the 4 injectors, the fuel rail, pressure release valve, and pressure sensor...
since, the car don't start ... it run for 1 or 2 seconds, then stall...
i Can only run the car with maf unplugged .
but it idles Bad, stft at +25, afr at 21 and not really want to rev up.. but if i can go UP to 3000 RPM, then the engine run fine ( afr ok, vacum pressure ok )
i found no air leak ( smoke tested, and also soapy water tested, sprayed brake cleaner everywhere in the engine bay did noting..
if is spray in the air box, then the engine idles fine for a few seconds..
i replaced maf, Map, replaced again the manifold gasket, now i did injector seals ..
i still have to problem...
if someone have an Idea ..

 

Post a picture of your engine bay please, specifically the area where the air filter is.
Edit:
Did this start happening randomly or after parts were changed/replaced or has it always happened since you got it?

 

initiale, the car was fine, but i had huge fuel leak betwin injector and fuel rail, when i removed the rail, i have seen it was dead, there were holes in the rail where O-Ring are.. (sorry for m'y english)
so i replace everything...
since the car stall...

 

So you had the intake manifold off.... Check for gaps between intake manifold and head, and make sure the gasket isn't torn or cracked or anything.

 

hi, i've removed everything, i put corksport injector seals ( the Cooper ones )
i test all 4 injector with multimètre, 1.3 ohm each.. i have removed egr pipe and blanked egr ports ( screw on the manifold and plate on the egr pipe output ) egr is still plugged.

i put the rail, manifold, and everything back, and i have the same issue...
manifold gasket looks fine,
i can't start it with maf sensor plugged...
if i unplug it, it idles at 800 to 900 RPM, with afr at 20, vacum at -0.2, -0.3 bars, instead of -0.8, and fuel pressure at 600-700psi
i Can make it rev if i press and release gaz pedal a few times, the engine run better and better wile revs go up, afr goes down, and vacuum goes down, and as soon as it pass over 2500 -3000rpm, afr goes black to normal and vacuum goes to -06, --07 bar,,
then i Can make it rev up, afr and vacuum are fine, if i wot, it revs without missfire, fuel pressure goes UP to 1900psi,
if i press gaz pedal a little, just to keep it at 3000 RPM it run fine, but if i let it go under 2500 it missfire again, and nearly stall.
if i turn ac on, it's worst, it is hard top make it rev to 3000, but AT higher RPM it runs fine also.
today i have replaced the crankshaft position sensor, right in the middle of the 20th tooth,
and it does nothing better...
i have also noticed, that the boost pressure Nevers go to positive values, but i don't remember if it was the case when reving in neutral Gear ...(mine is a manual 6 speed gearbox)
i also notice that when it missfires, there is back pressure in the airbox , i Can feel the air pushed out by the air duct comming from the airbox near the headlight.

if i resume: no found leaks...Map maf crankshaft, and camshaft sensor all.new.
injector seals, o-rings, injector, fuel rail, pressure release valve, fuel pressure sensor all New...manifold gasket New.
throttle body working ( it close well and open when gaz pedal presses )
egr deleted blanked...
and the exhaust flow at rear muffler seams good... no white or blue or black smoke..
i'm out of ideas...
thanks to all of you that tries to help me...
best regards
al

 

hère is the picture..
there is epoxy on the hpfp plastic part on top, as the top of the plastic part seized a little when unpluging it,, so i put epoxy on it before it breaks completely..
the problem isn't there, as it was not broken until now... lol

 

Post like ten different pictures of the engine bay so we can actually see what's going on

 

This is quite odd to me, sounds like it's also backfiring by the air coming out of the intake? Perhaps time for a leak down test if it's pushing air out Enki and EB would know than me, I want to draw attention to this issue

 

Could just be recirc air.

With the car idling, is any air trying to go into or out of the hybrid bypass valve (silver thing with the cone on it in your above pic). If it's sucking air in, that's your issue.

 

you mean the blow off valve, can fail and suck air into the intake ?
that's a 2 way one, a Big part goes recycle and a few air goes out.. the spring for thé free to air ouput is a hard one, i mean, it make noise only if i lift gas when boost is over 1 bar... (14psi)
it was working good before i removed fuel rail and intake.. but i will check it.,

for the leak down test, do you think piston rings could be worn or dead?
the car was just runing perfect and no issues at all before injector leak... that will be no luck at all ...

i for my Bad vacuum AT idle, inhave -0,2 bars at idle (something like -3psi )
and when it run fine, i have -0,8 bar ( about -14 psi )
do you think it can be piston rings that make such a Big drop?
the most strange thing is that i have -3 psi AT idle, with missfire, afr at 20 and stft at +25.. and when i pass over 3000 RPM vacuum goes back to -14psi and it run good..afr under 14 and stft near 0...

 

hi, i opened my bov, nothing damaged, the seals are good, the piston moves freely,
the spring is good ..nothing strange here...