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Old 01-07-2009, 05:52 PM   #1
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Default Swapping back to stock ECU

do I need to put the ST SIGN fuse BACK in the fuse box now that I am going back to stock ecu? That is the fuse you MUST remove from the fuse box when installing MSPNP.

Thanks
-Ryan

p.s. Just doing this to pass smog since I have the standalone.
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Old 01-07-2009, 06:03 PM   #2
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Think so.

And you can pass smog with a standalone MS.... I've done it and no, I didn't know the guy.
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Old 01-07-2009, 06:06 PM   #3
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Originally Posted by ThePass View Post
do I need to put the ST SIGN fuse BACK in the fuse box now that I am going back to stock ecu?
That fuse is in series with a signal that tells the ECU you are cranking over on the starter. It'll run without it, but cold starting might be a bitch.

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p.s. Just doing this to pass smog since I have the standalone.
I passed CA smog with 440cc injectors on mine.
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Old 01-07-2009, 06:07 PM   #4
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How?? I'm nearly certain that for a smog inspection the tech has to plug into the diagnostic plug in the engine bay and if I'm not mistaken their computer or whatever reads the ecu and checks for CEL's and such - the MSPNP doesn't even talk to that diagnostic plug unless I'm totally mistaken.

Any more info on this???

-Ryan
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Old 01-07-2009, 06:38 PM   #5
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They only plug into the diagnostic plug if you have a obd2 ecu. If you have a greddy it is VERY likely your factory ecu was not obd2 since they started that in the US with the 95 miatas.
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Old 01-07-2009, 06:52 PM   #6
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They only plug into the diagnostic plug if you have a obd2 ecu. If you have a greddy it is VERY likely your factory ecu was not obd2 since they started that in the US with the 95 miatas.
Oh. I forgot about that...
Well, stock ecu is back in now. I figure the ref is probably very ---- about stuff - more so than a normal smog guy so it's all back to how greddy intended... except that I left the intercooler in the car and just swapped out the piping so the intercooler is hanging out not connected to anything
I think next time I'm up for a smog I'll try to pass with the MSPNP as this month I'm switching to 460cc injectors so swapping back to the stock ecu would require swapping injectors too.

-Ryan
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Old 01-07-2009, 07:27 PM   #7
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except that I left the intercooler in the car and just swapped out the piping so the intercooler is hanging out not connected to anything
you now have an interfooler
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Old 01-07-2009, 08:36 PM   #8
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it's all back to how greddy intended... except that I left the intercooler in the car and just swapped out the piping so the intercooler is hanging out not connected to anything
Boy, that sounds familiar. I used to do the exact same thing (leave the IC in place, but remove all the piping and re-install the plastic tube) and I even had the blue Vortech FPR hanging on the firewall and plumbed in, though it was gutted internally.

So, what did you do that you have to see the Ref? My last check was a test-only, but I never got busted all the way back to the state dude.
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Old 01-07-2009, 08:57 PM   #9
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I got pulled over by a CHP who thought my car looked modified enough to warrant being pulled over. Anyways, I didn't have the CARB sticker with me, so I got the ticket. Went to court today with the CARB sticker in hand and the judge said I had to go to the ref.

OK I have a big issue now - drove the car around with the stock ecu in and the original greddy tubes hooked up to the black oem crossover tube and now I have a CEL!!! Not good as a CEL will fail the smog. What in the world about what I did could cause a CEL?
All I did was:
unplug MSPNP/Plug in stock ecu
Plugged vac hose that goes to the MSPNP MAP sensor with a nail
put a 10amp fuse into the ST SIGN slot
Remove my IC piping and install greddy/stock pipes
Set idle
Set base timing to 10* with stock ecu in
Plugged the charcoal canister back in since I had removed that.

Can a vacuum leak cause a CEL? Because it drives/idles fine but the boost gauge won't go below -10 psi and it normally goes as low as -30 psi on off throttle...

Please help!
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Old 01-07-2009, 09:07 PM   #10
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ugh. this kind of **** by itself is enough to keep me from moving to california. it sounds like a vaccum leak, or that your MAF is acting up.
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Old 01-07-2009, 09:49 PM   #11
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What in the world about what I did could cause a CEL?
It'd help if you knew what the fault code was for.

Open the diagnostic connector on the driver's side shock tower and put a jumper between TEN and GND. Turn the ignition key to on, but do not start the engine. Observe the flashing sequence of the CEL to learn the code.

List of codes here: Miata Computer Diagnostic Fault Codes
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Old 01-08-2009, 12:45 AM   #12
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Thanks for that info didn't know how to read the code.

it is code 15 - Oxygen sensor (output too low)

My stock o2 sensor is still there - the wideband is mounted farther down the exhaust. What does this mean? I recall that when installing the megasquirt or the wideband I did something to the stock o2 sensor... not remove it, but maybe disconnect it? I'm working int he dark now so should be fun trying to get a flashlight up under the fender to get an eye on the harness that plugs into the o2 sensor...

UPDATE: FIXED! I remember that when I installed the wideband for one reason or another I disconnected the stock 02 sensor wire - probably because the MSPNP can't be getting two 02 signals. So, I went out and plugged it back in. Wallah!

Thanks x1000000 Perez for the info on reading the codes that was the life saver!!!!

-Ryan

Last edited by ThePass; 01-08-2009 at 01:20 AM.
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Old 01-08-2009, 10:36 AM   #13
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you now have an interfooler
Ricer!!
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