Runs better without map sensor???
08-13-2009, 06:05 PM
#1
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Runs better without map sensor???
Why does my car feel like it has a miss at idle and light throttle up until about 2500 rpm, yet when I unplug the map sensor, it runs smooth as can be? Yes, the check engine light comes on when i do that and it resorts to default values in the PCM, but it just runs so much better. I have watched the map values on a scanner and they seem to be good. Changed plugs and wires and damn near everything else on it. It just doesnt make sense. Anyone have any ideas???? 93 vette 6 speed. pretty much stock.
08-18-2009, 07:01 PM
#6
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It has had this light miss ever since i owned it. It isn't tuned other than to remove egr and emissions. Put a new map sensor on the other day and it still feels the same. Could it be my non vented opti causing an issue? Some days the miss is worse than others.
08-18-2009, 09:23 PM
#7
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A 93 running without a MAP would have to be running in some kind of limp-home mode.
Is the bad behavior in closed loop or open loop or both?
If only in CL, then you're throwing it out of CL and it's probably the O2 sensors.
Is the bad behavior in closed loop or open loop or both?
If only in CL, then you're throwing it out of CL and it's probably the O2 sensors.
08-19-2009, 08:42 AM
#8
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Does it in closed loop or open loop. New AC Delco O2 sensors as well. I thought maybe an optispark problem, but it wouldn't make sense why it idles and revs perfect with the map unplugged. It is in some sort of limp mode with the map unplugged as it is not really driveable that way, however, it will idle and rev up fine that way. Just has me confused.
08-19-2009, 12:56 PM
#9
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Look at the front, right side of the block where the coil and ICM mount.
You should have a few black ground wires on one of the bolts/studs.
Back it out, clean the terminals and block surface with a piece of sandpaper.
Add a little dielectric grease and tighten. See if that helps any.
You should have a few black ground wires on one of the bolts/studs.
Back it out, clean the terminals and block surface with a piece of sandpaper.
Add a little dielectric grease and tighten. See if that helps any.
08-29-2009, 08:06 PM
#10
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Look at the front, right side of the block where the coil and ICM mount.
You should have a few black ground wires on one of the bolts/studs.
Back it out, clean the terminals and block surface with a piece of sandpaper.
Add a little dielectric grease and tighten. See if that helps any.
You should have a few black ground wires on one of the bolts/studs.
Back it out, clean the terminals and block surface with a piece of sandpaper.
Add a little dielectric grease and tighten. See if that helps any.
08-30-2009, 03:29 PM
#11
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Corvettes are set up a little different than F-bodies i guess. I know what area he is talking about but my vette only has 1 wire there. Cleaned it up and still the same issue. What doesn't make sense is like in the title, i pull the map sensor plug and it idles perfect. Wouldn't that rule out any ignition or mechanical problems?
08-31-2009, 05:14 PM
#12
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I'm going through the same problem with my 95 , my map is currently unplugged because it misses so bad plugged in. I'm waiting on a new pigtail connector for it because the clip is broken on mine, ordered the little seal from the dealership today. If that doesn't work I will be getting a new map. I was getting a code 33 before I unplugged it
Last edited by SmokeyBlaZe; 08-31-2009 at 05:16 PM.
09-01-2009, 10:40 AM
#13
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Today when I started my car with the map unplugged it dropped down to about 500 rpms and cut off, then When I started her back up she was slowly bouncing between 500-1500 rpms. Is this from the map being unplugged?
09-01-2009, 02:26 PM
#14
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Basically, one of the things it isn't using in limp home mode may be the cause. But it's using almost nothing in limp home mode, so that doesn't narrow it down much.
09-01-2009, 03:05 PM
#15
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Anyone have any idea as to what the default values are in limp home mode, such as coolant temp, inlet air temp and others? These are used to calculate normal fuel and timing, so curious what they change to, to make my car idle so much better in limp mode. Might help me find what sensor is bad.