ok i got my car back from mazda after a service which i had hoped would solve my boosting problems but it didnt. I just took it for a run and the car will not go over 0 vacuum.

When it approaches 0 the car starts to hesistate and backfire a little. Has anyone experienced this ever.

As for grabbing codes ive openend the diagnositcs box but dunno which one to join?

 

in the box you join gnd and ten as far as what you exp it might be something called limp mode. Try reseting your ECU.

 

yeah ive already resetted the ecu.. its a used one. Do you know what the black box above the ecu does?

 

oh, and you can't use the flashing engine check light to get the codes - as we don't have one! haha, rpm-powa pointed that one out for me :p

do a search under his name (I think I spelt it right) - as he has posted the procedure before - if it doesn't go into the specifics for JDM (it's a bit more of a pain in the butt) - PM him

 

hahah damn.. off boost the car drives perfectly which is a good sign. i really do think its something electrical related.

The BOV does go off even on 0 vacuum.

 

rpm_pwr (pete) is the correct username (thankfully!)

I'll qoute him:

"Open the diagnostics port in the engine bay. Connect TEN and GND with a link. If you have a fast voltage meter, you can read the voltage on the FEN pin on the diags connector. Alternatively, just buy an LED and a 680 Ohm resistor and solder them together. Put one end in the FEN pin socket, and the other in +BAT. Like so:
FEN <----- 680R------|< (LED) ------ +BAT

A paperclip works best for the TEN->GND link and is about the right thickness to make good contact with the terminals. Quite a few people have PM'd me about that post and I have since found out that you can use a test lamp if you couldn't be arsed making the LED. "

the code list has been posted on this forum a few times

good luck!

 

my guess would be that you appear to have a major boost leak. the reason the car stumbles when you get to that point (0 vacuum) is because the ecu is either sensing boost or "anticipating" boost and richening the mixture to the point that the car is misfiring due to the extra fuel that is being provided because of the ecu "thinking" the car is boosting. try hooking your boost guage up closer to the turbos along the intake path and see if you get a boost reading. if so, then you know the leak is between your guage and the uim.

 

If he is in Japan, he might have a 96 or later which I believe is OBDII. Might want to confirm the year of his car before he starts trying to code his engine by plugging a wire in somewhere.

 

Check your y-pipe and other hoses conected to your turbo's

 

Yeah when one of my IC rubber pipes blew off, I was getting 0 boost. Wouldn't go past 0 on the gauge. Check your IC pipes.

 

they didnt have obdII on the rx7. thats why they stopped importing in 96, they didnt want to spend billions to make it obdII to sell 500cars...

 

Cool. Plug away then!

 

its limp mode,,,,leaking boost wouldnt cause back firing. thats exactly what my car run like in limp mode,,,,car would drive fine but wouldnt let you boost,, pull the error code using the procedure described by daiOni.

 

wouldnt a boost leak cause stalling?? mine doesnt stall at all.

 

Have you also checked your turbo actuator arms? I had similar problems with my twins and realized that one of them had come off.

 

You know...what I don't understand is...When people get a boost leak and then they experience stalling and smoking they say...The map sensor popped off...But what's the difference between the map sensor vac line popping off and any other vac line attached to the UIM popping off? They are all getting the same pressure/vac from the same source...So if any of those pop off the UIM then the same symptoms would occur...Right?...This may be a bit off topic...

 

map sensor pops off, the ECU doesn't know how much fuel to put in. ex. Line pops off, and map now sends 0psi to the ECU (atmosphere), so ECU dump 0psi amount of fuel, no matter if the motor is sucking in 15in-hg (needs less fuel) or push 10psi...well, that would pop the motor.

 

Because the MAP sensor is what the ECU uses to determine manifold pressure. When the hose to the sensor pops off the ECU now has no idea what the manifold pressure is...


As for the problem this guy is experiencing, no boost and backfiring is a sure sign of limp mode. Car pulls normally until boost starts to build and then instant cutout and backfiring.

My car just was stuck in limp mode for a day when the feedback sensor on my OMP went south (actually I could maintain 3psi. Anything over that and instant cutout). I verified the OMP was working fine but of course couldn't get out of limp mode until replacing it. If you're patient you can maintain 65 mph on the highway in limp mode. Do yourself a favor and use a downhill on ramp as I did though

 

Ok, I understand this part...But whether it pops directly off the sensor or off another nipple on the manifold you should get the same symptions right? Like say, you have your boost gauge hooked up to the nipple right on top of the manifold...If that popped off it would affect the map sensor, correct?....

Don't know if anyone mentioned this to you before but a Mazda dealership will usually give your car back to you in worse shape than when you dropped it off there. Don't take it to dealership anymore.

 

No. All you'd have is a very small vacuum leak that would probably have no noticeable effect. Everything else would be perfectly fine.

 

I had same symptoms and found that it was double throttle solenoid/check valve. Just disconnected it and could boost normal.

 

all i had done at mazda was an oil and filter change, spark plugs and power steering fluid. Didnt think that was gonna cause too much problems =)

I have a feeling its limp mod too. Now i just have to figure out why. Thanks guys ill keep you all updated.

 

dude, do you have cats? my car wouldn't go past 0, it backfired, etc, I unclogged cat and whoalaaaa, boosting, 12' again!!!

 

I had one of my secondary injectors go bad once. My car would fall flat on its face at 0 manifold pressure. It would also sputter out at about 4000 RPM even if I was keeping in the vacuum.

-Max

 

did you do any work to the car before this started or did you buy it that way?