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Old 10-18-2014, 01:37 PM   #1
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Default MSPNP map sensor help

Hi, I have a gen 1 mspnp and I'm having map sensor trouble. When the car is running (like crap) the map sensor gauge on tuner studio doesn't move. It's stuck on 100kpa. So when I change the map sensor gauge to a vacuum gauge its stuck on 0. I have changed the map sensor over for a new one (250kpa) and its exactly the same :/ can anyone help me? If it wont work could I rig up a external map sensor?
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Old 10-18-2014, 08:13 PM   #2
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Wait, what is your MAP sensor hooked up to? It should be teed off the FPR vac line. 100kpa means your map sensor is (likely) working and it's sitting open to the atmosphere. 0 PSI = roughly 100kpa or so.

There's nothing on a Miata that will pull vaccum to 0 kpa. A boost gauge hooked up to nothing obviously reads 0 PSI.
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Old 10-19-2014, 04:28 AM   #3
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It's hooked up to where the carbon canister was
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Old 10-19-2014, 11:24 AM   #4
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Has it worked before?
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Old 10-19-2014, 12:42 PM   #5
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No it hasn't, that's why I changed the map sensor to a new one
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Old 10-19-2014, 12:49 PM   #6
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But this is a new ecu for you? The car has never ran well on this ecu?
Is the correct map sensor selected in the project properties?
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Old 10-19-2014, 01:54 PM   #7
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Your MAP gauge reads something, something that just happens to be right in the middle of it's range. It also just happens to be reading atmospheric pressure, which I highly doubt is a coincidence. Why exactly is it you think it's broken? Disconnect it from whatever you have it hooked to and blow/pull on the line while logging in tunerstudio.

You actually pulled the MSPNP apart and soldered in a new MAP sensor?
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Old 10-19-2014, 02:39 PM   #8
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Quote:
Originally Posted by deezums View Post
Your MAP gauge reads something, something that just happens to be right in the middle of it's range. It also just happens to be reading atmospheric pressure, which I highly doubt is a coincidence. Why exactly is it you think it's broken? Disconnect it from whatever you have it hooked to and blow/pull on the line while logging in tunerstudio.


You actually pulled the MSPNP apart and soldered in a new MAP sensor?
I tried this, sometimes it spikes to 230kpa on idle, so with the engine running I disconnected the vac line and it stayed at 100kpa, usually on idle the intake manifold should be under vacuum, when I rev the car the gauge on tuner studio doesn't move, I have logged this and ill post it on here after work. Yes I removed the map sensor on the board and ordered another 250kpa from diyautotune and the results are the same. I have noticed that the car doesn't start up unless I change the map type to 115kpa using engine constraints

Yes I pulled it apart and found that the Q5 (fuel pump) transistor was blown, I've repaired it now, also the db37 loom joining the boards had not been making a good connection properly so I built a new loom using new db37 plug ends. Now the ecu operates better. Before it was randomly shutting off on me, Now its on as it should be.
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Old 10-19-2014, 02:57 PM   #9
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Here's a pic of the map gauge, look the gauge says its spiked to 250kpa which is impossible for a stock engine lol
The vacuum gauge says 0 too on the right of the map gauge

Attached Thumbnails
MSPNP map sensor help-wp_20141018_16_06_21_pro_zpsf62aa079.jpg  
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Old 10-19-2014, 03:06 PM   #10
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I guess it could really only be three things, you don't have it hooked to the manifold, something about the MSPNP is toast, or you've somehow got the MAP calibration wrong in tunerstudio.

I'd find the datasheet to the MAP sensor and go probing. If one transistor is blown, maybe the Vref is blown, or traces melted? It should be easy as hell to bench test, just get a syringe, small section of vac line and a meter.

You could easily wire in another MAP sensor, but you'll need the pinout to retrofit it. Wouldn't be much more work to just test it first...
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Old 10-19-2014, 04:15 PM   #11
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Quote:
Originally Posted by deezums View Post
I guess it could really only be three things, you don't have it hooked to the manifold, something about the MSPNP is toast, or you've somehow got the MAP calibration wrong in tunerstudio.

I'd find the datasheet to the MAP sensor and go probing. If one transistor is blown, maybe the Vref is blown, or traces melted? It should be easy as hell to bench test, just get a syringe, small section of vac line and a meter.

You could easily wire in another MAP sensor, but you'll need the pinout to retrofit it. Wouldn't be much more work to just test it first...
What's a Vref? And which transistor would I need to test buddy?
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Old 10-19-2014, 04:22 PM   #12
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I'm not up on it 100%, but there should be a section of the MSPNP that makes a regulated and fixed voltage, that voltage is used as a reference for the map sensor to work, as it puts out an analog voltage based on pressure. If the reference voltage is incorrect or dirty, the MAP will not read right. Reading the datasheet of the map sensor should help. I don't know your MSPNP, so I can't give specifics. You'll need to find the pinout, and trace things back. If you can measure a solid voltage between ground and Vref pin on the MAP, it's probably OK. The signal pin on the sensor should change voltage (in relation to signal ground) as you use the syringe to cycle the MAP sensor.

I still think you have it hooked up wrong. You should buy a 3/16 vacuum fitting T, put it between the FPR and it's manifold source, run it through the firewall, and plug it to the MSPNP.

People don't use the charcoal canister or CC port for a reason.
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Old 10-19-2014, 04:31 PM   #13
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http://rocky.digikey.com/WebLib/Moto...A%20SERIES.pdf

Vout is the signal, it should change in relation to ground based on pressure.

Gnd is obvious, it's where you should be measuring voltage against.

Vs is the reference voltage, it should be 5V and should not fluctuate at all. If you follow the trace, it should take you to the transistor "making" said 5V.
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Old 10-19-2014, 08:37 PM   #14
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Simple test:

Key on, engine off. Connect a piece of hose to the MAP sensor, put the other end in your mouth, and suck on it. With no suction, the computer should show around 100 kpa. With your mouth, you should be able to draw it down by at least 20-30 kpa, much more than that if you're a typical Miata owner.

If that test fails, you have an electrical problem.

If that test works, re-connect it as normal, and repeat the suck test on the other end, where the hose is connected to the engine.
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Old 10-19-2014, 08:44 PM   #15
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Quote:
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, much more than that if you're a typical Miata owner.

.
PHAHAHHAHAHAHHAAHHHAAAA!!!
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Old 10-20-2014, 06:07 PM   #16
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Quote:
Originally Posted by deezums View Post
I'm not up on it 100%, but there should be a section of the MSPNP that makes a regulated and fixed voltage, that voltage is used as a reference for the map sensor to work, as it puts out an analog voltage based on pressure. If the reference voltage is incorrect or dirty, the MAP will not read right. Reading the datasheet of the map sensor should help. I don't know your MSPNP, so I can't give specifics. You'll need to find the pinout, and trace things back. If you can measure a solid voltage between ground and Vref pin on the MAP, it's probably OK. The signal pin on the sensor should change voltage (in relation to signal ground) as you use the syringe to cycle the MAP sensor.

I still think you have it hooked up wrong. You should buy a 3/16 vacuum fitting T, put it between the FPR and it's manifold source, run it through the firewall, and plug it to the MSPNP.

People don't use the charcoal canister or CC port for a reason.
Thankyou ill give this a try tomorrow and let you know the results
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Old 10-23-2014, 01:02 PM   #17
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I've repaired the megasquirt I now been driving it for a while 😊
The pin2 gnd on the map sensor was burnt so I repaired the gnd track and voila the car runs perfectly!
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Old 10-23-2014, 01:28 PM   #18
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Good to hear you got it fixed, wonder what caused it to blow up in the first place? Did you forget the ST_sig fuse? I did that
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Old 10-23-2014, 01:44 PM   #19
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Nope lol the st sign fuse blows the q5 transistor for the fuel pump. The stock ecu was never ment to run the fuel pump but the boffins as diyautotune figured out how lol
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