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Unread 12-21-2008, 08:51 PM   #1
greenerob
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Symptons of a bad MAP Sensor

I recently had issues with my Jeep and there were many suggestions along the way as to what it may be. With all of the help I narrowed it down to a bad TPS or bad MAP. In the end with more help I decided that it was the TPS which it turned out being. One of the replies sent me to a webpage that showed what the various sensors do. I am just trying to get more educated on all of this Jeep stuff.

What are the symptons of a bad map sensor?

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1995 Jeep Wrangler Rio Grande 4in RC Lift 33" Tires with 73,000 miles. Auto Trans
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Unread 12-21-2008, 08:55 PM   #2
Kraxen
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i just changed mine today after doing a motor swap but turn your key in the on position 3 time but not enough to start and the check engine light will flash a code. thats how i found out mine was bad.
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Unread 12-21-2008, 08:57 PM   #3
Kraxen
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caused mine to run like crap if i got it running
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Unread 12-22-2008, 05:05 AM   #4
greenerob
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Quote:
Originally Posted by X-YJ-X View Post
caused mine to run like crap if i got it running
Define crap
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Unread 12-22-2008, 06:44 AM   #5
Alfons
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It can run very rough at a very low rpm and normally die. If you pull the vacuum line to the map sensor, you'll hear what "crap" sounds like. A failing or malfunctioning MAP won't always give you a "check engine light", it depends on what's going "bad" in the sensor.
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Unread 12-22-2008, 07:05 AM   #6
Que89YJ
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Bad Map

Symptoms for a bad MAP Sensor would be comparable to an old vacuum advance on a distributor. The timing retards because the ECM thinks demand is low (typical failure is low).
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Unread 05-27-2009, 08:55 PM   #7
dswi
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Would this (a bad MAP Sensor) cause no power (sporadically) between 1500 and 2000 RPM when I am above about 30 MPH??
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Unread 05-28-2009, 05:29 AM   #8
Que89YJ
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No Power

Map or the TPS, I would check fuel rail regulator first though.
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Unread 06-02-2009, 06:45 PM   #9
dswi
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Quote:
Originally Posted by Que89YJ View Post
Map or the TPS, I would check fuel rail regulator first though.
Pep boys pulled codes of always lean running...
What causes the engine to know to run lean or rich...is it MAP or TPS...or both
(My O2 sensor is bad and is unplugged)...I am having problems in the lower RPM range (below 1500 or so)...If I rev to about 3000 I have a little power...(don't want to do this too long...as to not wear out the clutch pressure plate!).
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Unread 06-02-2009, 06:46 PM   #10
dswi
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Will the engine still run with the fuel rail reg valve unplugged from vacuum?? Mine won't (is this right or not?)
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Unread 06-05-2009, 02:13 PM   #11
dswi
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Quote:
Originally Posted by Que89YJ View Post
Map or the TPS, I would check fuel rail regulator first though.
It was the TPS...

EVERYTHING IS RIGHT WITH THE WORLD AGAIN!!
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Unread 09-03-2011, 12:11 PM   #12
swelms
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I have a similar problem. I listed it in these forums http://www.jeepforum.com/forum/f13/1...thing-1260551/ trying to narrow it down if anyone could help plz
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Unread 05-10-2012, 05:41 PM   #13
kman99
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Anyone come up with a fix for this? My 93 YJ is doing the same exact thing. It runs great if its cold out and until it gets up to temp. After driving on the highway for 10 miles or so, it cuts out like it is running out of gas and if I try to give it more gas it will backfire. I have replaced the fuel pump, fuel filter, MAP, TPS and fuel pressure regulator. The O2 sensor is only two years old and I don't have any error codes. Can anyone help?
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Unread 05-11-2012, 10:55 AM   #14
Que89YJ
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It is either your O2 sensor or the exhaust manifold to the O2 sensor has loose bolts or cracks. I know you said you replaced it but the issue is happening when it goes into closed loop and starts to use the readings from the sensor.
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Unread 10-16-2012, 09:36 AM   #15
For33l
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Quote:
Originally Posted by kman99 View Post
Anyone come up with a fix for this? My 93 YJ is doing the same exact thing. It runs great if its cold out and until it gets up to temp. After driving on the highway for 10 miles or so, it cuts out like it is running out of gas and if I try to give it more gas it will backfire. I have replaced the fuel pump, fuel filter, MAP, TPS and fuel pressure regulator. The O2 sensor is only two years old and I don't have any error codes. Can anyone help?
I know this is old but if you haven't fixed the problem it could your timing chain, if its never been replaced it could be stretched beyond belief. Thats what was wrong with mine and mine had the same problems.
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