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Old 06-26-2016, 07:30 PM
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Engine miss around 1200 RPM at times

Hello All,
I have a 2001 Jeep Grand Cherokee that I've put a salvaged 4.7L engine in. Just to let everyone know what has been done to it here is the list. The engine has all new gaskets, new timing chain guides, new spark plugs, new coils, new MAP, new IAC, new O2 sensors, Injectors have been removed and cleaned and checked against a new injector for flow and pattern - all seems good there. I've chased all the coil wires and injector wires from the PCM to each component with 12 volts to insure continuity and that the common ground is good - no problems there.

The issue I'm having is after starting the Jeep and it goes into its closed loop function I get an engine stumble about 1200 RPMs. Sometimes the engine catches and will continue to idle and other times the engine will die. It is easily restarted. There are other times when this occurs I get a P0352, P0356 code.

Included is my scanner information for the last 3 measurements prior to the engine dying:
Numbers of DTCs 0
Fuel system 1 statusCL
Fuel System 2 statusCL
Calculated Load Value(%)2.0
Engine Coolant Temperature(。F)195
Short Term Fuel Trim -Bank 1(%)-5.5
Long Term Fuel Trim - Bank 1(%)2.3
Short Term Fuel Trim -Bank 2(%)-4.7
Long Term Fuel Trim - Bank 2(%)2.3
Intake Manifold Absolute Pressure(psi)4.5
Engine RPM(rpm) 776
Vehicle Speed Sensor(mph)0
Ignition Timing Advanece for #1 Cylinder(。)0.0
Intake Air Temperature(。F)138
Absolute Throttle Position(%)9.0
Location of Oxygen SensorsB1S12--B2S12--
OBD requirements to which vehicle is designedOBDII
----------------------
Numbers of DTCs 0
Fuel system 1 statusCL
Fuel System 2 statusCL
Calculated Load Value(%)2.4
Engine Coolant Temperature(。F)195
Short Term Fuel Trim -Bank 1(%)-14.1
Long Term Fuel Trim - Bank 1(%)2.3
Short Term Fuel Trim -Bank 2(%)-11.7
Long Term Fuel Trim - Bank 2(%)2.3
Intake Manifold Absolute Pressure(psi)4.2
Engine RPM(rpm) 221
Vehicle Speed Sensor(mph)0
Ignition Timing Advanece for #1 Cylinder(。)4.0
Intake Air Temperature(。F)138
Absolute Throttle Position(%)16.5
Location of Oxygen SensorsB1S12--B2S12--
OBD requirements to which vehicle is designedOBDII
----------------------
Numbers of DTCs 0
Fuel system 1 statusCL
Fuel System 2 statusCL
Calculated Load Value(%)1.6
Engine Coolant Temperature(。F)195
Short Term Fuel Trim -Bank 1(%)-12.5
Long Term Fuel Trim - Bank 1(%)2.3
Short Term Fuel Trim -Bank 2(%)-11.7
Long Term Fuel Trim - Bank 2(%)2.3
Intake Manifold Absolute Pressure(psi)14.2
Engine RPM(rpm) 0
Vehicle Speed Sensor(mph)0
Ignition Timing Advanece for #1 Cylinder(。)4.0
Intake Air Temperature(。F)140
Absolute Throttle Position(%)8.6
Location of Oxygen SensorsB1S12--B2S12--
OBD requirements to which vehicle is designedOBDII
----------------------
Numbers of DTCs 0
Fuel system 1 statusCL
Fuel System 2 statusCL
Calculated Load Value(%)0.0
Engine Coolant Temperature(。F)195
Short Term Fuel Trim -Bank 1(%)-12.5
Long Term Fuel Trim - Bank 1(%)2.3
Short Term Fuel Trim -Bank 2(%)-11.7
Long Term Fuel Trim - Bank 2(%)2.3
Intake Manifold Absolute Pressure(psi)14.2
Engine RPM(rpm) 0
Vehicle Speed Sensor(mph)0
Ignition Timing Advanece for #1 Cylinder(。)0.0
Intake Air Temperature(。F)140
Absolute Throttle Position(%)8.6
Location of Oxygen SensorsB1S12--B2S12--
OBD requirements to which vehicle is designedOBDII
----------------------


Sorry for the long message and I have appreciated the help in times past from this forum. Hopefully one day I'll have enough knowledge on these things to be of help to someone.

Again, thanks for any assistance that can be provided.
Scott

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  #2  
Old 06-27-2016, 10:12 AM
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Re: Engine miss around 1200 RPM at times

Every time that is misses, you get the P0352 and P0356 codes? These codes mean that the primary ignition part for the respective #2 and #6 cylinders have a problem. Did you already check the connectors on the PCM itself for moisture/corrosion and eventual loose fit for the pins? You did measure the wires for continuity and short to ground, while messing with the bundle? Does the problem start only after being into closed loop?
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  #3  
Old 06-27-2016, 03:53 PM
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Re: Engine miss around 1200 RPM at times

I don't always get the P0352, P0356 codes when it misses. In fact, it can run for 5 - 10 minutes prior to getting the code. I do get the miss regardless of whether it is in open or closed loop. I did check the pins on the PCM and they looked good. I didn't check the resistance of the wire, but I did power 12 volts through the wires and measured the reading. I used a ground to battery for the initial reading then I used the common ground through the wiring harness and everything worked well.
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Old 06-28-2016, 09:17 AM
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Re: Engine miss around 1200 RPM at times

A couple of items that may or may not be pertinent. I the TPS last night for correct voltage, etc. and here is what I got. With the ignition on, but the engine not running I got 5.1 volts when checking the voltage supply line and using the ground to the TPS. I then back probed the signal wire and got .45 volts at closed throttle. As I opened the throttle I got a pretty smooth increase of voltage to WOT which topped out at 3.8 volts. So I believe my TPS to be working correctly.

The second item has to do with my autozone heating / A/C controls. I don't any display nor do I have any fan or lights there at all. Not sure if that is a related issue or something altogether different.

Thanks,
Scott
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