Need more...AEM/MT readings off (search didn't fix it) & Cold Cranking/Start Issue - Miata Turbo Forum - Boost cars, acquire cats.

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Old 11-19-2008, 10:35 PM   #1
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Default Need more...AEM/MT readings off (search didn't fix it) & Cold Cranking/Start Issue

Ok, two things.

1)
AEM and MT are not reading anywhere near where they should. The gauge in MT wont read above ~ 11.80, and the AEM gauge is reading full sweep.

I've changed the settings under Exhaust Gas w/e AND did the whole 9.72 to 10.02 in the settings, but it didn't change anything.
I have AEM linear picked in the config.
In MT, it is picked as a wideband.

I have the white 0-5v output wire going into my harness. Any other ideas?


2) Car will not crank cold by itself. The past two nights working on it, the only way I got it to fire was to pull the plugs, spray starter fluid stuff in the holes, put it back together and crank it. (which works like a champ, after it fires and runs for a second it idles OK, but really isn't fine until its completely warm...obviously an enrichment issue after start.)

Ambient temps are ~45F, same for coolant temps withing a degree or so. I'm running high res code with stock 90-93 MSPNP settings:

Should I just jack up the PW ~40 degrees? How high is ok without flooding? The other night they plugs smelled like fuel when I took them out, but it wouldn't crank until I used a starting fluid.
Also, in the realtime viewer and on the gauges, MS shows 0 PW and duty cycle while cranking...is that normal?

Name:  CrankingSettings.jpg
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I'm going to guess that the car might not be getting enough fuel since I'm having to put starting fluid or w/e in it...again, any ideas?

Last edited by miatamania; 11-19-2008 at 11:41 PM.
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Old 11-19-2008, 11:08 PM   #2
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Old 11-20-2008, 12:21 PM   #3
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Sounds like you need to increase the cold start cranking pulse widths a little.

On the issue of the sensor readings, be sure it's set up for the right sort of wideband in the MegaTune Configurator.
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Old 11-20-2008, 01:16 PM   #4
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I will make sure it is. In the config it was setup for AEM_Linear IIRC. I'll make sure. I'm also going to make 100% sure I have the right wire.

For cold start, should I just go up by .1 in the 40* column until the car fires or will I risk flooding it?
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Old 11-20-2008, 01:46 PM   #5
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post your msq, curious to what your are settings are. when you talk about the whole 9.72 to 10.02 thing, are you refering to the settings.ini file?


since you need start fluid, it's pretty obvious you need more fuel while cranking, start adding a point in the 40 and 60 degree temps rows and see what happens.
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Old 11-20-2008, 02:51 PM   #6
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The 9.72-10.02 is referring to changing the settings.ini file

I didn't even think about touching the 60* settings.
When they are in between temps do they just average or find a happy medium, or go to the closest?

I'll grab my MSQ when I get back home. I gotta figure out how to get them off a laptop run win98 that wont read my flashdrive x.X
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Old 11-20-2008, 03:35 PM   #7
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MS always averages between cells...ve fuel table, boost duty cycle, spark table, warmup table, cranking table, air-density corrections table....
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Old 11-20-2008, 03:45 PM   #8
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I assumed it did, not sure why I didn't think about that when trying to work with cranking.

I think I might skip my next class and go work on the bitch.
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Old 11-20-2008, 03:46 PM   #9
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but there's obviously something wrong if MT and the AEM aren't even close to the same scale, which good easily f-**** up.
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Old 11-20-2008, 07:19 PM   #10
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I checked the settings, Config shows it setup for AEM linear.

Only thing I can think of is we wired in the wrong input? instead of 0-5V.
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Old 11-20-2008, 08:42 PM   #11
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Quote:
Originally Posted by Braineack View Post
but there's obviously something wrong if MT and the AEM aren't even close to the same scale, which good easily f-**** up.
Yeah, its not leaving jackstands until I figure that out. Which sucks, because I want to drive my car :(
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Old 11-20-2008, 09:14 PM   #12
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wheres that msq?
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Old 11-21-2008, 12:25 AM   #13
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Perchance, have you verified that the switch on the back of the AEM is set to position 0? Were it set on a 0-1V scale, you'd see just about exactly the readings you describe.

Failing this, some basic troubleshooting steps are in order. First, disconnect the AEM's analog output from the MS's O2 input. Run a temporary jumper from the MS's Vref output (pin 26) to the O2 input. This will place +5 on that input,
which should cause MT to indicate 20:1.

If that works, then the problem is likely with the AEM or its wiring. If not, then start investigating inside the MS. Specifically, I'd verify that R10 and R11 are the right values- these two form a voltage divider on the WBO2 input, and the wrong values here (R10 > 1k, or R11 < 1M) would cause the abnormally low (rich) readings you're seeing.
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Old 11-21-2008, 12:40 AM   #14
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Quote:
Originally Posted by Braineack View Post
wheres that msq?
Trying to figure out how to get win98 to accept my flashdrive so I can pull files OFF of my laptop.
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Old 11-21-2008, 12:58 AM   #15
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Quote:
Originally Posted by Joe Perez View Post
Perchance, have you verified that the switch on the back of the AEM is set to position 0? Were it set on a 0-1V scale, you'd see just about exactly the readings you describe.

Failing this, some basic troubleshooting steps are in order. First, disconnect the AEM's analog output from the MS's O2 input. Run a temporary jumper from the MS's Vref output (pin 26) to the O2 input. This will place +5 on that input,
which should cause MT to indicate 20:1.

If that works, then the problem is likely with the AEM or its wiring. If not, then start investigating inside the MS. Specifically, I'd verify that R10 and R11 are the right values- these two form a voltage divider on the WBO2 input, and the wrong values here (R10 > 1k, or R11 < 1M) would cause the abnormally low (rich) readings you're seeing.
I have not checked the back of the gauge I will try to do that tomorrow, but it reads full sweep (seems normal operation) will that happen regardless? Or does that just change the output?

About the other stuff, I'll need to figure out what that means. I will have to check the output first as that is easy.
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Old 11-21-2008, 10:01 AM   #16
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Quote:
Originally Posted by miatamania View Post
I have not checked the back of the gauge I will try to do that tomorrow, but it reads full sweep (seems normal operation) will that happen regardless? Or does that just change the output?
Honestly, I don't know. The whole time I ran the AEM, I never bothered to actually throw that switch and see what happened. The documentation seems to infer that only the analog output changes, which I base upon the fact that they've indicated the various LED positions to be a constant for all switch settings:


Perhaps I'll get the AEM setup back out, jam the sensor up the tailpipe, and experiment with it.


Quote:
About the other stuff, I'll need to figure out what that means. I will have to check the output first as that is easy.
Heh... It's not that hard, we're just moving a couple of wires around to feed a fixed +5 signal into the MS, which it should interpret as 20:1. If it does, then the MS is OK and the AEM is bad. If it still shows <20:1, then there's something wrong in the MS. We're just bisecting the problem in half, so we know where to troubleshoot further.
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Old 11-21-2008, 10:30 AM   #17
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Test complete. I got out my old AEM gauge, inserted the sensor up the tailpipe, powered it externally, and connected a voltmeter to the analog output. As I expected, the front-panel display functions in linear wideband mode no matter what. The rear-panel calibration affects only the analog output. I also found, by comparing the AEM display to the LC-1 display, that readings taken post-cat are surprisingly accurate. There was a discrepancy of a few tenths between the two, so I wouldn't trust it for tuning, but based upon this I expect that a dyno could be properly calibrated to show correct AFR in a post-cat application. I've always wondered about that.

You can easily verify the setting of your UEGO by watching the display during powerup. If it's set in 0-5v mode, the display will show P00 after the initial warmup. If it shows P01-P04, you're in the wrong mode.

Incidentally, I was surprised to find that the rear-panel cal is not a switch at all, but a potentiometer. There are no markings on the case either, you just twist it with a screwdriver while observing the front panel until you hit the correct mode. My respect for AEM has shrunk.
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Old 11-21-2008, 12:52 PM   #18
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hmmm. Awesome.

Thank you sir, I will def take a look as soon as my road gets salted and we can get one of our vehicles out of the driveway. -.-

Sorry for all the dumb questions. I can turn a wrench ok, but this stuff I know nothing about, at least I'm learning.
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Old 11-21-2008, 01:15 PM   #19
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When you start the car, or power it up, the Aem gauge tells you what it is set to. It will flash P0, P1, P2, etc. If it's set to something other that p0 or p1 it is sending the wrong readings to the MS.

Yes. This a ridiculously basic suggestion and likely everyone knows it. I just hadn't seen it made yet. Everyone is talking about taking the gauge out and checking the switch. I figure 1st things 1st in case that hadn't been checked yet.
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Old 11-21-2008, 01:47 PM   #20
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^joe made it somewhere up. But it def should be checked before anything else.


Figured out the cold start issue, I had to go from 8.2 in the 40* section to a little over 10. and from 7.5 in 60* to almost 9.
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