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Greg, Technician
Category: Jeep
Satisfied Customers: 7111
Experience:  maintain jeep wrangler's for a off road rental company,
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1996 Jeep Grand Cherokee Laredo: 6cyl 4.0..recently replaced..muffler

Resolved Question:

I have a 1996 Jeep Grand Cherokee Laredo 6cyl 4.0 with poor engine performance. I recently replaced a bad Cat converter and muffler. I'm currently getting the codes 12 - 43 - 37 - 21 - 45 - 22 - 55
I looked up the codes but that doesn't help on what to fix.
Submitted: 5 years ago.
Category: Jeep
Expert:  Greg replied 5 years ago.
Name is XXXXX XXXXX i will assist you the best i can, please Only accept if you are happy with my answer.

Is the car drivable , as i would like you to take a drive down to AutoZone and get a free code read out done , as your jeep is OBDII .

As soon as you have the codes please post them here for me.

Kind regards Greg
Customer: replied 5 years ago.
Ok here's the codes autozone pulled, P1762 - P1757 - P0138 - P0141 - P0300 - P0304 - P0118
The truck runs though lacks power when going from a stop. Sometimes usually when engine is cold it will not leave the lower gears ( its a automatic) and the engine will just race. Stopping and shifting through the gears, park to low 1 back and forth a few times corrects it.
Hope this helps.
Customer: replied 5 years ago.
Also just found the ccv/pcv vacuum house the one towards the cabin rotted at the connector it was just placed in it.
Expert:  Greg replied 5 years ago.
Hi .

Thanks you for the codes this will make it a lot easier to start repairs for your issue .

First we have to repair the P)300 P0304
Which means you have a multiply misfire and a main misfire on cylinder # XXXXX

So we have to start with the basics ,
Spark plugs ,wires etc , this you have done so this is a good start ,but you still have a problem .

Next what has to be done is check the fuel pressure ,

If the fuel pressure is good then we have to check the injectors ,

Easiest whey to do this is remove the #4 injector and swap it over with the # XXXXX .
clear the codes then run the engine and see if the code changes to #6,(P0306) if this is the case you have a bad injector and this will have to be replaced .

Then you have the codes:

P1757 - Governor Pressure Above 3 PSI When Request Is 0 PSI

P1762 - Governor Pressure Sensor Offset Improper Voltage

These are transmission issue and both codes are pointing towards the governor pressure sensor; in most cases this part has to be replaced but best checked first with the diagnostic scan tool just to be safe and not end up replacing parts not needed .

P0138 - P0141 These are your down stream sensors on the exhaust which is probably a bad sensor or a wiring issue short to ground or short to voltage . So this system will have to be checked out .

P0118 is a ect issue meaning a coolant sensor malfunction or a wiring issue .

To be honest you need a good diagnostic scan tool to check these issue out otherwise you will end up just replacing parts with nor good results and spend a fortune for nothing .

So my advise for the problem you have is to take it to a known good shop that works on Jeeps to have this checked out for you. or visit the Jeep dealer .

But if you have a diagnostic tool i would be more than happy to walk you though this repair .

Kindest regards Greg.
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