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Old 06-18-2009, 11:26 PM   #1
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ok,
so i was stumped as to why when my motor was cold it was reading extra lean, and when it was hot it read extra rich.

aside from air temp and coolant temp corrections, i noticed something strange.

when it is cold the map seems to be much lower, 25kpa @ idle, 98kpa @wot. Yet after it heats up idle is 45ish kpa, and wot increases to 120ish kpa.

do you think i have some sort of weird vacuum leak?

stock 2000 w/ gm 3bar map sensor
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Old 06-19-2009, 12:01 AM   #2
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Sounds more like a faulty sensor. ~100kpa is atmospheric pressure, so you shouldn't be going over that at WOT. Where is the sensor mounted?
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Old 06-19-2009, 12:42 AM   #3
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Quote:
Originally Posted by swimming108 View Post
ok,
so i was stumped as to why when my motor was cold it was reading extra lean, and when it was hot it read extra rich.

aside from air temp and coolant temp corrections, i noticed something strange.

when it is cold the map seems to be much lower, 25kpa @ idle, 98kpa @wot. Yet after it heats up idle is 45ish kpa, and wot increases to 120ish kpa.

do you think i have some sort of weird vacuum leak?

stock 2000 w/ gm 3bar map sensor

How did you wire it up? If a MAP sensor is bad its just bad, and if its ok its usaully ok.

When its cold its reading right, and when its hot, its way off. Is it mounted where it would get extremely hot?

Just so you know, even if everything is reading perfectly you have to throw what would seem to be a ridiculous amount of coolant trim at the motor to get the right AFR's. My new tunes I've uploaded should have a coolant enrichment I used with my vehicle. Since its percentage it should scale with any injector size correctly.
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Old 06-19-2009, 05:51 PM   #4
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the map sensor is mounted at the base of the strut bar on the drivers side. Is this too close to the manifold?

I was planing on relocating it closer to the fender anyways, i think this gives me good enough reason to follow through with the relocation.


I will look through your more recent maps and take note of the temp corrections travis.
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Old 06-19-2009, 06:21 PM   #5
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My MAP sensor is mounted beside the map sensor that is used for the egr. Its just before the place you just described. If I understood you right, I don't think that your sensor is mounted in a wrong place.
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Old 06-19-2009, 08:47 PM   #6
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the map sensor was originally mounted to the strut bar where the red arrow is pointing.

it is now mounted further away from the heat, as indicated by the yellow arrow.

i will update later as to whether or not this has any effect on the obscure readings that i was referencing to earlier.
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Old 06-20-2009, 12:09 AM   #7
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ok, even with the map sensor in the new location i am still getting issues.

when i first started up the car and for the first 30-45 min max vacuum was 15-19kpa idle was about at 28-34kpa, wot was 98kpa.

After about an hour of tuning the wot map started to increase. by the end of the session wot was at 115 kpa, and idle was at 45-55 kpa, and max vacuum was at 30 kpa.
At this point, my infared temp gauge said that the map sensor was at 90* F.

Just for curiosity sake, after the tuning session with the motor off, i hooked up a spare hose to the map sensor. Atmospheric pressure read 115, and the min and max that my lungs could produce where 78kpa and 122kpa.

so do you guys think that the map sensor is faulty?
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Old 06-20-2009, 12:03 PM   #8
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i just rechecked the map sensor since it is cooler this morning 75.8*f.

atmosphere reads 98 kpa, fast idle (1550 rpm) is reading 32kpa, wot reads 98kpa, and max vacuum reads 20kpa.

also for consistency sake the max and min that mu lungs can produce are 105 and 75 kpa.

so what is the deal with these differing values? the temperature difference is 20*f or so, yet the map changes rather drastically.

anyone have any ideas?
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Old 06-20-2009, 04:19 PM   #9
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Try checking the voltage between the sensor ground and engine ground when it goes to the higher readings. It might be something in the sensor ground path is increasing in resistance when it gets hot.

Are the sensor wires run directly to the adaptronic?
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Old 06-21-2009, 02:07 AM   #10
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i wired the sensor exactly how it was described in the instalation instructions. the power is from the TPS, and the sensor is wired to the mass airflow sensor's wire.
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Old 06-21-2009, 04:44 AM   #11
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Sorry I didn't use the instructions

What about the ground, is at the TPS as well?
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Old 06-21-2009, 11:28 AM   #12
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yes power and ground are both from the TPS.

should i check to see if there is a difference between this ground and some other one?
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Old 06-21-2009, 11:54 AM   #13
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This is pretty odd, and I definitely appreciate Roach's expertise here.

I'm getting ready to make an order, and I could get you another MAP sensor just to try it. The GM sensors are supposed to be 99% stable over a really wide operating range from -20-250F or something along those lines, which you are definitely outside of on the pressure tolerence.

If you can't find anything wrong with the ground in the connector then its more the likely the sensor. The grounds are directly to the ECU as far as I can tell from the wiring diagram. How are your solder connections/wire connections?
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Old 06-21-2009, 01:08 PM   #14
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I have two types of connections... Wires soldered directly together, and wires soldered to bullet style connectors.

The MAP power and ground are soldered directly to the TPS power and ground. The signal wire from the MAP sensor is connected by bullet connector so that i can switch back to the MAF sensor easily. This connection is very tight, and requires that i use pliers to get the bullet connector apart.

I will check to see if there is any resistance within my connections.
I don't think that i will be able to post the results from this test until next Thursday. I an getting hitched this afternoon and will be back from my miniature honeymoon by then.

Thanks everyone for all of the great help that you have given me thus far.
I will be switching back to the stock ECU for reliability purposes until next Thursday. So until then...
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Old 06-21-2009, 01:14 PM   #15
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Congratulations!

I just came back from a wedding, it must be in season.

I should have the new sensor here for you by then either way so if its not the grounds I'll have you fixed up in no time.
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Old 06-21-2009, 04:40 PM   #16
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Quote:
Originally Posted by swimming108 View Post
yes power and ground are both from the TPS.

should i check to see if there is a difference between this ground and some other one?
ya, when it gets hot check the voltage between the TPS (as close as you can get) and the Map ground (also as close to the sensor as possible). This is just to make sure that the wring is sound when it gets hot. If it measures 0V then you've ruled out the ground, and can try a new sensor.

Congratulations on getting hitched!
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Old 06-30-2009, 12:24 AM   #17
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thanks guys,
i have had enough fun and i will be getting back to work on the car now. i will also update as soon as i have either checked the ground or tried another sensor.
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Old 07-03-2009, 10:48 PM   #18
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TravisR, i just received the new map sensor. I am extremely happy to report that i no longer have an issue with the map values rising due to heat.

idle is at 16kpa and wot is now roughly 83kpa.

83kpa seems a little low for atmospheric pressure, any idea how i can get that number closer to 100kpa? Or is that even necessary?

thanks a million,
Jared
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Old 07-03-2009, 11:03 PM   #19
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Jared,

You need to goto the analog tab and adjust your sensor just a bit. When the motor is off, but the ignition is on so that the sensors are reading select the upper value to be 100kpa and then click learn. Leave the lower value alone unless you have a vacuum gauge and vacuum generator to set it. By honing in on the upper value you will get the readings much work close to correct and it will give you the two points you need for the map sensor to be calibrated. The upper value doesn't represent the maximum it can read, it will still work like a full 3-bar.

Your welcome!
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Old 07-03-2009, 11:11 PM   #20
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ooh, cool
i will try that right now!

i will also try looking around for a shop that has a vacuum generator and gauge to do the same with the lower values.

cheers
-Jared-
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