Just purchased 2006 grand cherokee limited 4.7 liter engine . Misfire occurs


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I am receiving these codes on the problem. p2320,po113,po300,po308,poo68. I replaced all of the plugs gaping at 40 and replaced the4 ignition coil pack in cylinder 8. Have been trying to locate o vacuum leak that sounds like one when engine is running. But no success. Any suggestions. HELP PLEASE

Jared B

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Staff member
After you replaced the plugs and coil pack did you clear the codes? I know it's a basic question but just trying to start from the beginning to help out as best as I can.

If so, try swapping the coil on cyl 8 around with another one and see if the code moves. P0308 is a misfire on Cyl 8 code, while p0300 is a random misfire code. If you swap the coil on cyl 8 with cyl 7 the code should switch to a p0307 in theory if the coil is the culprit for that code.

Possible causes Faulty Intake Air Temperature (IAT) sensor, Dirty air filter Intake Air Temperature (IAT) sensor, harness is open or shorted, Intake Air Temperature (IAT) sensor circuit poor electrical connection

The generic trouble code P0068 refers to an engine management problem. A disparity exists between the computer's sensors as to the volume of air entering the intake manifold. The PCM relies on three sensors to indicate air flow volume in order to calculate fuel and timing tactics. These sensors include the mass airflow sensor, throttle position sensor and the Manifold pressure (MAP) sensor. There are many sensors on the engine however these are the three associated with this code. The mass airflow sensor is located between the air cleaner and the throttle body. Its job is to signal the amount of air passing through the throttle body. In order to accomplish this, a thin piece of resistance wire the thickness of a hair stretches across in the inlet of the sensor.

The other codes are all ignition related as previously stated so I figured we could look into these ones. P0013, points directly at the intake air temperature sensor but p0068 could relate to 3 different sensors. The GC 4.7 doesn't use a mass air flow sensor so we can rule that out right off the bat which leaves us with the throttle position sensor and the Map sensor. It could very well be the MAP sensor that would be causing your vacuum leak which would make sense if you're getting a MAP code as well as a vacuum leak.

To check for a vacuum leak you can spray a solution of soapy water around the engine with it running, a vaccum leak will start giving off bubbles so it should be easy to spot. If you have access to a smoke machine that is the best way but most don't and a soapy water solution would work just fine and won't hurt anything.

I had a 2001 Grand Cherokee with the 4.7 previously and my mom currently has an 06 with the 4.7 as well, something I noticed with both is that they suck air so hard through the throttle body at idle that with the hood open they sound like they have a vaccum leak, without actually having one.

All those codes together would make me think there's possibly a wire harness issue, or unfortunately possibly no compression in one of the cylinders.

There aren't many mechanics on here, and a great resource for jeep owners is https://www.jeepforum.com if nothing I've said helps, there are a lot of knowledgeable guys over there. Hopefully you get it fixed up. (y)

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