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Old 05-07-2012, 11:36 PM   #1
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Default GM IAT installed, but now car wont start

Trying to replace the stock MAF with the GM IAT onto the 1.6 before we turbo, just to have the car running well just before the major swap. Problem is that as soon as we connect the IAT sensor, the car wont start. If we go back and plug in the stock maf, car turns right on, no problem. Updated the resistor tables, Tunerstudio reads gauge values correctly. No idea why its doing this.

Anyone have any ideas?
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Old 05-07-2012, 11:41 PM   #2
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That's strange. Mine worked on the first try.

What MS are you using? Where do you have the IAT wired? How and why?

Throw some pics up of your engine bay, as well, so we can see what chaos you hooligans have started.
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Old 05-08-2012, 12:23 AM   #3
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diypnp.

the 2 wires from the IAT sensor are in #1 and #5 in the maf connector plug as the directions say.
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Old 05-08-2012, 03:07 AM   #4
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The iat is attached to a section of aluminum pipe, and I basically removed the stock airbox/maf, and attached the new iat pipe at the end of the stock plastic pipe that connected to the airbox, and then put a regular cone air filter to the other end.
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Old 05-08-2012, 10:39 AM   #5
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did you recalibrate the AIT sensor in the software?
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Old 05-08-2012, 12:08 PM   #6
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I used the settings on diyautotune and ohm rate of 2490

Temperature Ohms
48 degrees F 7000
87 degrees F 1930
146 degrees F 560

Went back and forth between stock and iat [re-calibrated each time] and it works stock but doesn't when i plug iat in [again I recalibrate the IAT settings I posted above]. Any thoughts? Seems very weird.
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Old 05-08-2012, 12:10 PM   #7
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what are your temperature readings? are they accurate?

just use the "GM" sensor from the drop down when calbirating, dont plug in anything.
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Old 05-08-2012, 01:44 PM   #8
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Ok I will try that when I get back home. The temps do appear and seem somewhat normal I think?? It read around 70F and I think the stock MAF read similar. But the temps were definitely within range, nothing out of the blue.
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Old 05-08-2012, 01:49 PM   #9
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Pretty easy to check, if the IAT temp reads close to ambient when the car is cold, Its probably working.
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Old 05-08-2012, 01:58 PM   #10
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Quote:
Originally Posted by jtpaintballwdp View Post
Pretty easy to check, if the IAT temp reads close to ambient when the car is cold, Its probably working.
Then if that is the case, then the IAT itself is working. I live in socal and it was around the 70s yesterday, car was cold. So it's gotta be the calibration settings. I will try choosing GM as mentioned and go from there.

Thanks again everyone for the help so far.
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Old 05-08-2012, 02:39 PM   #11
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wait a second.

how are you controlling the fuel pump?
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Old 05-08-2012, 03:29 PM   #12
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Quote:
Originally Posted by Braineack View Post
wait a second.

how are you controlling the fuel pump?
Not sure I understand?

The fuel pump is controlled through ms i would assume? We installed megasquirt, took out the ST SIGN fuse and the car has been running fine like that for weeks.

The only thing that recently changed was adding the 460 injectors, which ran fine after fuel adjustment. Next thing we added was the IAT, and it refuses to run unless the stock MAF box is installed.
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Old 05-08-2012, 03:33 PM   #13
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Quote:
Originally Posted by kruze View Post
Not sure I understand?

The fuel pump is controlled through ms i would assume? We installed megasquirt, took out the ST SIGN fuse and the car has been running fine like that for weeks.

The only thing that recently changed was adding the 460 injectors, which ran fine after fuel adjustment. Next thing we added was the IAT, and it refuses to run unless the stock MAF box is installed.

did you build the diypnp? did connect FP to high side driver IN, then high side driver OUT to 1c?
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Old 05-08-2012, 03:45 PM   #14
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Quote:
Originally Posted by Braineack View Post
did you build the diypnp? did connect FP to high side driver IN, then high side driver OUT to 1c?
I would bet that you are correct and did not build the fuel pump circuit and when he unplugs the MAF that the fuel pump is not turning on.
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Old 05-08-2012, 03:59 PM   #15
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Quote:
Originally Posted by Braineack View Post
did you build the diypnp? did connect FP to high side driver IN, then high side driver OUT to 1c?
Hmm, we did solder it together yes, and at the time we built it so it would run the car stock. Does building that circuit prevent the stock MAF from running the car? I'll have a look at the circuit.

The temps read within 2-4 degrees of each other with either sensor plugged in, and I believe I did try it with just choosing the drop down "GM" option in tuner studio without changing anything and it still would not run.
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Old 05-08-2012, 04:01 PM   #16
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no it doesnt, but it allows the FP to be run when the AFM is not present.


right now, your issue is no power to your fuel pump.
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Old 05-08-2012, 06:08 PM   #17
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The wiring is correct. FP to 'in' on high side, 'out' goes to 1C. Does it matter which 1C terminal it's wired to? Currently its run to the smaller section of 1's, directly above the ecu connector.

Could the car run without this being wired properly?
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Old 05-08-2012, 06:37 PM   #18
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put ait back in.


jump f/p gnd in diagnostics.
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Old 05-08-2012, 06:45 PM   #19
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Quote:
Originally Posted by Braineack View Post
put ait back in.


jump f/p gnd in diagnostics.
Okay, should i try starting it as well or just listen to see if it begins running?
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Old 05-08-2012, 06:47 PM   #20
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Quote:
Originally Posted by kruze View Post
Okay, should i try starting it as well or just listen to see if it begins running?
It will start and stay running.
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