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MAP Sensor Testing; OK, I'm confused?
Topic Started: Jan 27 2013, 04:53 PM (3,322 Views)
XFIGUY
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Hi all,
say, I read on this forum, one way to test my MAP sensor on my 1992 Metro is to simply unplug the electrical connector while the car is idling. Then if the car runs worse, that would be a good indication that MAP is operating correctly.

I did just that. At a warmed-up idle, I unplugged it, the engine almost died, but then it caught it's self and perked back up kept idling, but it idled at a little slower RMP then when it was connected. So, I guess this test turned out to be a bit confusing for me, seems it didn't really tell me much. Any experts out there who can tell me if what I explained would mean a good or bad MAP sensor? I just don't know what to make of it...

Thanks for nay help anyone can provide me.

Bill.
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Memphis metro


I can tell you how your supposed to test it,

Turn the ignition on and at the light green wire going to the map sensor it should read 5 volts.

Disconnect vaccum hose at the map sensor and connect a vaccum pump. Turn igniton on and check voltage on the light green/red wire terminal. Apply vaccum and note voltage changes. As vaccum changes, voltage should change. Readings should be 1-1/2 volts at high high vaccum using the pump or engine at idle. 4-1/2 volts at full open throttle, low vaccum. In other words you should see voltage change using a vaccum pump with the ignition on at the light green/red wire terminal. Depending upon how much vaccum with the vaccum pump it should be between 1-1/2 volts to 4-1/2 volts.

If you do not own a vaccum pump, you can borrow one from autozones loan a tool program for free,

http://www.autozone.com/autozone/accessories/OEM-Vacuum-pump-and-gauge-tester-includes-24-in-tube/_/N-25jr?itemIdentifier=2080_0_0_


Why do you think its bad?



.
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XFIGUY
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Hey blue rhino, thanks much for your straight forward, easy instructions on this.
I not so sure my MAP is bad. My 1992 is an XFi, it isn't getting the MPG's it should, so I'm trouble shooting the problem. Here's my issue. On the highway, @ 55 / 60 mph I get around 45 MPGs. it's compression is good at around 186, 184, 181 PSI. So it should be doing a bit better then that. I'm running Conoco premium, (NO ethanol). I've gone through many of the common issues that can cause poor MPGs, not much left to look at other then 02 sensor and the MAP sensor. I've read the MAP can play a big part in MPGs, so here I am...I have done some testing with a digital meter myself, but I wasn't real clear about the proper way. I think I did conclude one thing in testing, in reference to what you posted. "Turn the ignition on and at the light green wire going to the map sensor it should read (5 volts). If I did this step correctly, I was getting around 4.5 volts, not 5 volts. My battery isn't the best, in a good float charge stage it's hangs around 12.3 volts, and that's not so good. So could that by chance give me a low voltage show on the MAP test that's requiring 5 volts?
Any ideas?

Thanks much man!

Bill.
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HelterSkelter
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you get better mpgs from regular. there is less energy in premium. there's one problem solved.
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Memphis metro


4.5 volts is ok as long as it variates using a pressure pump.
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XFIGUY
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HelterSkelter
Jan 27 2013, 09:28 PM
you get better mpgs from regular. there is less energy in premium. there's one problem solved.
Well,
I guess a guy learns something every day, or, much of what I think I know or believe is wrong!

I just searched and found this info that seems to back your claim, I did not know this!

The American Petroleum Institute says that premium gasoline can give your better mileage because premium contains more energy per gallon. However, the gain in fuel efficiency is so small that you will likely not even notice the difference, according to Cars.com. The Federal Trade Commission also believes that premium gasoline has no effect on fuel mileage, according to a report by USA Today.

Unfortunately, where I live, Conoco gas stations only offer their NO ETHONAL fuel in their premium grade, not regular. Now I'm thinking that maybe 10% ethanol fuel may get as good MPGs as no ethanol?

Thanks for the help guys!

B.

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Vkhelldog
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45 mpg is what the cars rated at. You can pass 50 mpg if you change your driving style and higher maybe with a few sime aero mods.
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XFIGUY
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Vkhelldog
Jan 28 2013, 10:19 AM
45 mpg is what the cars rated at. You can pass 50 mpg if you change your driving style and higher maybe with a few sime aero mods.
Yes, the base Mertro models are rated at or around 45 or so, mine is an XFI, the XFi are rated higher, at or around 58 or so.
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5 O'Clock Charlie
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I think your doing pretty good XFIGUY ...... Unless your getting a code 31 or 32 or having some drivability issues, I'd think your MAP sensor is all right.


As far as your milageage is concerned, try slowing down a bit, and remember MGP in winter months is always a little poorer.

http://www.fueleconomy.gov/feg/noframes/8704.shtml

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XFIGUY
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5 O'Clock Charlie
Jan 28 2013, 06:32 PM
I think your doing pretty good XFIGUY ...... Unless your getting a code 31 or 32 or having some drivability issues, I'd think your MAP sensor is all right.


As far as your milageage is concerned, try slowing down a bit, and remember MGP in winter months is always a little poorer.

http://www.fueleconomy.gov/feg/noframes/8704.shtml

Posted Image
Well thanks for that 5 O'Clock Charlie!
I'm glad you brought up the code thing. I live in a small community, I've called all over local repair shops and such trying to find someone who can look at codes. They all tell me, my 1992 is to old for their equipment to hook up to. So, how do you guys do this code procedure?

Thanks,
Bill.

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Memphis metro


XFIGUY
Jan 28 2013, 06:39 PM
They all tell me, my 1992 is to old for their equipment to hook up to. So, how do you guys do this code procedure?

http://geometroforum.com/topic/638390/1/#new
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XFIGUY
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OK,
I ran the voltage tests as the last poster explained about the ECM or wiring issue, over my MAP sensor issue. This may not be good!

Firs off, I was unable to see any numbers for the little pin connections or cavities on the connector plug. There are 3 connections in the MAP plug, 2 of them are copper color the other is plain silver color. So, I'll go by the corresponding wire colors to the pin connectors. I tested all 3 connections.

Connection #1 the silver color connection inside the plug, or the plan green wire: (4.97 volts)
Connection #2 or the Green and Black wire: (0.01 volts)
Connection #3 or the Green and Red wire: (0.05 volts)
Yes, this was done with the plug connector (unplugged) and I did connect to the NEG post on my battery.

I hope I haven't just opened up a can of worms here!
Any ideas out there for me?

As always, THANK YOU ALL for the help, it's very much appreciated!

Bill.
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XFIGUY
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blue rhino
Jan 28 2013, 06:45 PM
XFIGUY
Jan 28 2013, 06:39 PM
They all tell me, my 1992 is to old for their equipment to hook up to. So, how do you guys do this code procedure?

http://geometroforum.com/topic/638390/1/#new
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5 O'Clock Charlie
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Hopefully these will help ......


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clarkdw


Thanks for the pages 5 O'Clock.
XFIGUY it may be time to start with the basics. One of the most common problems with the Metro is bad grounds. Before you go off chasing rainbows remove and clean with emery or a wire brush on a dremel every single ground you can find. The battery connections, the battery cable to trans, the cable from the trans to the body, the grounds on the back of the intake manifold below the throttle body the grounds on the ECM, etc. You get the picture. Many times this will itself cure a problem.
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