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Old 01-16-2009, 09:33 PM   #1
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Default Interesting MSPNP issue

So it's been about 10F today and yesterday in NJ. My daily driver has been sitting for 2 days because I've been driving my girlfriend's 94 that I just turbo'd earlier in the week. I go to start my car tonight, it starts and stalls right away. I figure maybe the cranking settings are to blame so I adjust them as I've never fine tuned them at this temp. Still won't start. I check out all the gauges in MT and notice the vac/boost gauge is showing 44psi while the key is on but engine isn't running.

I disconnect the ECU and bring it in the house to warm it up. I figure maybe there was moisture in the vacuum line and some made it's way to the MAP sensor and froze. Of course freezing water expands which would/could exert pressure on the sensor and cause the extreme reading. After warming the thing up with a heat gun I bring it back outside. Car starts up immediately. Oh, and the MAP reading was dead on before starting.

So does this theory sound plausible or could it be something else?
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Old 01-19-2009, 11:53 AM   #2
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Could be ice in the sensor. Are you able to adjust the MSPNP so the sensor is pointed straight down? That may help.
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Old 01-19-2009, 11:59 AM   #3
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It happened again the next day as it was still like 16F. This time it wasn't as bad though. Was reading 104kpa at idle(very shitty idle at below 10afr) and I watched it slowly go down as the car heated up till it was normal. Cold spell is over and hasn't happened now that temps have been upper 20s-30s.

Unless I pull the factory harness up or move the MS to the front I can't rotate it to point the sensor is pointed down. If it happens any more I may consider those options though.
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Old 01-19-2009, 01:12 PM   #4
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Side note but I cranked my MS2 with it being 17 outside and it cranked and idled fine. Also my MS2 is oriented such that the map line does point relatively down.
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Old 01-19-2009, 01:42 PM   #5
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I wonder if you had some condensation in the vac line that was right at the edge of freezing and the sudden drop to low vacuum caused it to flash freeze. Makes sense why the sensor worked fine until you started it.
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Old 01-19-2009, 02:20 PM   #6
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Quote:
Originally Posted by Fidgitk View Post
I wonder if you had some condensation in the vac line that was right at the edge of freezing and the sudden drop to low vacuum caused it to flash freeze. Makes sense why the sensor worked fine until you started it.
Frozen water at 32*F at 1 bar would evaporate at 32*F and a vacuum. Not the other way around.
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Old 01-20-2009, 12:09 PM   #7
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I nuked my MSPnP MAP sensor last week. A few emails back and forth with DIY-AT pinopinted the issue. I ordered a new one locally (in the UK for 20 quid) and installed it, all my issues went away. Car started and ran perfectly.

This happened after a nasty cold snap. When I pulled my MAP line I had LOTS (5-10mm) of water in the line, so that seems quite conclusive to me.

I now have my MAP sensor pointing downwards, hopefully stopping condensation falling into the sensor (unless there is LOTS).

If this is indeed another failure then perhaps DIY-AT should mention it somewhere. They didn't seem tooo fazed by my issue, apparantly it was the first they had heard of it.
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Old 01-20-2009, 01:43 PM   #8
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Maybe they will now. Thank you for giving my theory some merit.
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Old 01-20-2009, 07:40 PM   #9
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whoa thats nuts.. certainly plausible though. thankfully that'll never happen in FL
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Old 01-20-2009, 07:58 PM   #10
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christ, I have a problem with one of my coils not working well when its below 30 out. I hate this cold weather.
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Old 01-21-2009, 05:34 AM   #11
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Another tip Paul. I needed to move my car 100 yards down the road with a broken MAP sensor. I was able to do this by changing my "Fixed ASE/MAP Time Period" to 60 seconds.

This setting fools the ECU into thinking it's got a fixed MAP value regardless of what the sensor is telling it. It is only used after cranking to get the engine running. The default is 5 seconds, and this is that part that is allowing your engine to start in the first place. But it dies as soon as it starts acting on the MAP input.

Might be useful to know. It dug me out a small hole :-)
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