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Unread 11-14-2011, 09:16 PM   #16
cruiser54
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1990 MJ Comanche 
 
Join Date: Oct 2009
Location: Prescott, Arizona
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2 seconds isn't too slow.

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Unread 11-15-2011, 12:35 AM   #17
Double0Jeep
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2000 XJ Cherokee 
 
Join Date: Nov 2011
Location: Mountain View, CA
Posts: 11
Ok, things are getting interesting now. The Jeep is now running so bad that it is no longer drivable. Good news is I finally got a CEL!

P0400 Exhaust Gas Recirculation Flow Malfunction

That bad news is that the 4.0L does not have an EGR Valve!! What going on here? Has anyone ever seen or heard of this before?

TIA!
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Unread 11-15-2011, 02:02 AM   #18
Double0Jeep
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2000 XJ Cherokee 
 
Join Date: Nov 2011
Location: Mountain View, CA
Posts: 11
Quote:
Originally Posted by Double0Jeep View Post
Ok, things are getting interesting now. The Jeep is now running so bad that it is no longer drivable. Good news is I finally got a CEL!

P0400 Exhaust Gas Recirculation Flow Malfunction

That bad news is that the 4.0L does not have an EGR Valve!! What going on here? Has anyone ever seen or heard of this before?

TIA!
It looks like this is just a symptom of the low engine vacuum.

P0400-P0405
The PCM tests the exhaust gas recirculation (EGR) system during deceleration by momentarily commanding the EGR valve to open while monitoring the manifold absolute pressure (MAP) sensor signal. When the EGR valve is opened, the PCM should see a proportional increase in MAP.

If the expected increase in MAP is not seen, the PCM notes the amount of error that was detected and adjusts an internal fail counter towards a fail threshold level. When the fail counter exceeds the fail threshold level, the PCM will set this DTC. The number of test samples required to accomplish this may vary according to the amount of detected flow error.
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4.0l , low power , rough idle , surging , vacuum

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