Map Sensor/Running Lean
CF Veteran
Joined: Sep 2010
Posts: 12,692
Likes: 6
From: Mercer County, NJ
Year: 2001
Model: Cherokee
Engine: 4.0L I6 HO
Np oh and when I said close your eyes I was just being a smartass. It wouldnt spark because all it does is discharge the energy in the ECU to ground. Good luck with your issue. Also check
Google for alternate ways to discharge the ECu power to reset the system. Good luck brother
Google for alternate ways to discharge the ECu power to reset the system. Good luck brother
Thread Starter
Junior Member
Joined: Jul 2012
Posts: 38
Likes: 0
Didnt work. Jeep surges then dies with map sensor plugged in. Unplug it and it runs.
Time to replace MAP sensor. Guess I'll have jeep test it, along with the 02 sensors and catalytic converter just so I know if anything else is wrong.
I'll post what they say and the results of my work.?
Time to replace MAP sensor. Guess I'll have jeep test it, along with the 02 sensors and catalytic converter just so I know if anything else is wrong.
I'll post what they say and the results of my work.?
Seasoned Member
Joined: Jun 2012
Posts: 369
Likes: 0
Model: Cherokee
You haven't replaced your thermostat lately have you? That wrangler I had was running rich becuase it had a 180 thermostat in it. I replaced it with a 195 and it didn't completely fix the problem but it got a lot better. Might be something to think about
Senior Member
Joined: Aug 2011
Posts: 760
Likes: 6
From: Landers, CA
Year: Several
Model: Cherokee
Engine: 4.0
OBD II - touching the cables together, stepping on the brake pedal, killing a sheep at midnight, sacrificing a virgin, or flashing lights, does NOTHING - INTERNET RUMORS = BULL!
THE ONLY way to reset the PCM is disconnect battery power for at LEAST 8 HOURS. Resets the computer to factory default.
Do it whenever you change sensors, make major changes, or repair the vacuum lines.
THE ONLY way to reset the PCM is disconnect battery power for at LEAST 8 HOURS. Resets the computer to factory default.
Do it whenever you change sensors, make major changes, or repair the vacuum lines.
Last edited by rrich; Aug 30, 2012 at 10:54 PM.
CF Veteran
Joined: Mar 2010
Posts: 47,923
Likes: 38
From: Broward County Fl.
Year: 1989 xj sport 2dr
Model: Cherokee
Engine: 12 hole bosch Injectors
OBD II - touching the cables together, stepping on the brake pedal, killing a sheep at midnight, sacrificing a virgin, or flashing lights, does NOTHING - INTERNET RUMORS = BULL!
THE ONLY way to reset the PCM is disconnect battery power for at LEAST 8 HOURS. Resets the computer to factory default.
Do it whenever you change sensors, make major changes, or repair the vacuum lines.
THE ONLY way to reset the PCM is disconnect battery power for at LEAST 8 HOURS. Resets the computer to factory default.
Do it whenever you change sensors, make major changes, or repair the vacuum lines.
CF Veteran
Joined: Mar 2010
Posts: 47,923
Likes: 38
From: Broward County Fl.
Year: 1989 xj sport 2dr
Model: Cherokee
Engine: 12 hole bosch Injectors
Senior Member
Joined: Aug 2011
Posts: 760
Likes: 6
From: Landers, CA
Year: Several
Model: Cherokee
Engine: 4.0
When running it without the line connected, the MAP no longer sends the right signal. Eventually the deep memory in the PCM tries to compensate as best it can.
When you reconnect the line, the PCM suddenly gets the right signal. But it takes TIME for the deep memory to adjust - till then it may surge, die or do other strange things.
Erasing the memory puts it back to default - it should run fine there. It will still tqke a few drive cycles to fine tune itself.
8 hour disconnect - other methods only clear codes, not the deep memory.
When you reconnect the line, the PCM suddenly gets the right signal. But it takes TIME for the deep memory to adjust - till then it may surge, die or do other strange things.
Erasing the memory puts it back to default - it should run fine there. It will still tqke a few drive cycles to fine tune itself.
8 hour disconnect - other methods only clear codes, not the deep memory.