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Author Topic: MAP sensor signal unstable  (Read 323 times)
Wreckleford
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« on: November 08, 2009, 07:15:51 AM »
The map sensor signal I am geting from the F/IC on board map sensor is very unstable. It fluctuates as much as 7-8 psi when the car is at peak boost. I am not sure if this is a prblem with the car or with the F/IC. The boost guage doesn't fluctuate at all but maybe it is too insensitive.

Now I want to clamp the factory map sensor, but when I do this and rely on the F/IC fuel map for additional fueling and use the ignition map to retad timing, the fuel and timing jump all over the place as the MAP signal jumps.

If I put a restrictor in the line would it dampen the MAP signal?
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Plug & Pray
Raj
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« Reply #1 on: November 08, 2009, 07:36:11 AM »
Have you tried moving the vac source?  Not to sure about using a restrictor since it might slow the response.  Might also want to try installing a mechanics style vac/boost guage for a reference.  Most aftermarket guages are dampened pretty heavily where as a mechanics guage isn't.
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Wreckleford
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« Reply #2 on: November 09, 2009, 05:35:11 AM »
Quote from: Raj on November 08, 2009, 07:36:11 AM
Have you tried moving the vac source?  Not to sure about using a restrictor since it might slow the response.  Might also want to try installing a mechanics style vac/boost guage for a reference.  Most aftermarket guages are dampened pretty heavily where as a mechanics guage isn't.

The car has a mechanical gauge and it shows no fluctuation. We moved the vacuum source to one right off the plenum (instead of tee'd off of another line) and we have the same effect.
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Plug & Pray
Wreckleford
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« Reply #3 on: November 10, 2009, 09:31:17 AM »
Am I the only one seeing this issue?
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Plug & Pray
Raj
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« Reply #4 on: November 11, 2009, 02:18:06 PM »
In vac, is the fic readind stable?  At part throttle in boost, is the reading stable?  Does the car have a custom intake/plenum? 

You really can't guage the fic reading against a autometer or other aftermarket mech. guage because they are dampened some.  Like I said before a mechanics vac/boost guage would be the best way to verify if its the motor or fic.
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Wreckleford
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« Reply #5 on: November 11, 2009, 05:20:22 PM »
When you said mechanics gauge I thought you meant mechanical gauge.

It is always a bit unstable, but gets realy unstable after about 4000 rpm. I notice the battery voltage is also very unstable so I wonder if that is part of the issue.
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Plug & Pray
Raj
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« Reply #6 on: November 11, 2009, 05:39:32 PM »
A mechanics guage is mechanical but has 0 dampening so you will see and fluctuations. 

Take a log of whats happening.
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Wreckleford
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« Reply #7 on: November 12, 2009, 06:22:29 AM »
Quote from: Raj on November 11, 2009, 05:39:32 PM
A mechanics guage is mechanical but has 0 dampening so you will see and fluctuations. 

Take a log of whats happening.

Yes, I know what it is, but I read your original post as mechanical and not mechanics.

I have several logs, it is form the logs that I know what the issue is. i will post a few of them.
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Plug & Pray
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