Intermittent Stalling/No Start (electrical?)

jms

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Hey all, I have a 2007 Liberty and hoping someone may have gone down this road before and could offer some advice. I'm having some serious intermittent issues which are almost certainly electrical in nature. They are:

  • Sometimes the Jeep will not start. It will act as if the battery was dead (no crank), but after several tries it may miraculously start perfectly. Sometimes it won't start for days, then out of no where, perfect.
  • Sometimes the Jeep will stall when idle OR when in gear. When this happens the engine simply cuts off. The only codes it has ever thrown are P1128 and P1129
  • Sometimes at idle (a stoplight for instance) the jeep will lurch forward suddenly as if I had pressed the accelerator (despite foot being on the break). This has been much less common the the other issues
Sometimes it is acting up and is basically undriveable because it's so unreliable, then weeks might go by where it is totally fine.

I have brought it to a shop and called several others (I live in Los Angeles), no one wants to touch it. They say it's too difficult for them to diagnose.

If anyone has some thoughts, I'd love to hear them. I'm not a mechanic, but willing to give stuff a try since at this point I'm ready to just accept a total loss on the vehicle, despite it mechanically being in excellent shape and running beautifully when it's not acting up.
 

Duster

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I think these are drive by wire throttles. In other words I don't think there is a mechanical throttle connection between the pedal and the throttle body.

That would probably be a place to start at least.
 

Billwill

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I agree with Duster^^^ the 2007 KJ is a drive-by wire-throttle which is known to give a lot of trouble!:(

At least re-plug any connectors on the throttle and on the PCM before replacing the throttle assembly.

Codes P1128 and P1129 are not listed in the 2006 KJ service manual which leads me to believe that these are relevant to the 2007 only...I do not have 2007 KJ Service Manuals.:confused:

You can try Google these two codes to see if there is a description for them...the KKs also use a drive-by-wire system I believe.
 

LibertyTC

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Online video suggests that both codes would appear in 6 cylinder engines. 1128 and 1129 relate to the oxygen sensors.
 

jms

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I agree with Duster^^^ the 2007 KJ is a drive-by wire-throttle which is known to give a lot of trouble!:(

At least re-plug any connectors on the throttle and on the PCM before replacing the throttle assembly.

Codes P1128 and P1129 are not listed in the 2006 KJ service manual which leads me to believe that these are relevant to the 2007 only...I do not have 2007 KJ Service Manuals.:confused:

You can try Google these two codes to see if there is a description for them...the KKs also use a drive-by-wire system I believe.

The PCM/throttle body are definitely logical places to start... but do you have any ideas other than just checking the connections at the plugs?

I have an OBD reader and a multi meter I could use to take some measurements.
 

jms

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Online video suggests that both codes would appear in 6 cylinder engines. 1128 and 1129 relate to the oxygen sensors.

Yea, it's a 3.7L. The codes are pretty ambiguous and not only related to the oxygen sensors...
 

Billwill

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As far as your first-stated problem of intermittent no-crank....the Actuator Pin Assembly may be starting to fail.

Or the interlocks going to the PCM may have a problem.

If you are stranded you can make sure you are in Park or Neutral, remove the Starter Relay from the Fuse/Relay box under the hood.

Briefly jumper together female pins 30 and 87 inside the empty socket...engine should turn over.
 

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