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Old 08-25-2014, 05:44 PM
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new to this forum problems with 07 5.7

new to this jeep forum. been trying to track down a problem with my 07 overland with 5.7. Runs fine cold, drive it for a while, park it in the heat then come back and it runs like crap. Seems to throw MDS errors and p0300 random misfire errors.
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Old 08-29-2014, 10:49 AM
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Re: new to this forum problems with 07 5.7

I have an 08 5.7 and my truck seems to drive slightly worse in the heat as well. The acceleration seems choppy, although mildly, at some points whem I am heavier on the gas. I have already changed Map sensor, PCV, EGR, Air filter, oil change, seafoam treatment, cleaned the throttle body, added a catch can. I was thinking of looking into crank position sensors and 02 sensors next. It doesnt seem to be a big problem but I want her to be perfect.
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Old 08-29-2014, 05:18 PM
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Re: new to this forum problems with 07 5.7

I would have a look at the upstream O2 sensors. Check the fuel trims, they should indicate single digit numbers.
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Old 08-31-2014, 09:27 AM
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Re: new to this forum problems with 07 5.7

Hmmm, did you by chance put in other than stock spark plugs ? The Hemi needs the hotter spark from copper plugs to run properly, and will misfire before long with aftermarket plugs like platinum or iridium, particularly in MDS mode.
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Old 09-02-2014, 05:36 AM
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Re: new to this forum problems with 07 5.7

I used the Champion 570's that are recommended.

As far as checking the 02 sensors, I have a OBII Bluetooth readout & the Torque app. When I look at the sensors the reading see way out of whack, mybe I have it set-up wrong.

It shows the following (I'm just trying to remember here, since I'm not hooked up to my car....)
F/T 1x1 - 3.9%
F/T 2x1 - 4.1%
F/T 1x2 - 99%
F/T 2x2 - 99%
F/T 1x3 - -%
F/T 2x3 - -%
F/T 1x4 - -%
F/T 2x4 - -%

It seems as though I'm reading this wrong or I have a huge problem. I will plug it in tonight and snap a pic of the readout to be sure I'm wrtiting this the right way. Also I thini pinpointed the exhaust leak to the metal to metal connection in the pipe behind the Y connection right before the huge muffler.
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Old 09-02-2014, 11:02 AM
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Re: new to this forum problems with 07 5.7

Lets wait for the screenshot then. The upstream sensors are the ones which should give the fuel trim values (so 1-1 and 2-1 sensors), which seems to be fine in what you wrote down.
The downstream sensors (1-2 and 2-2) are used for catalist monitoring and should not give any fuel trim figures.
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Old 09-03-2014, 02:51 PM
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Re: new to this forum problems with 07 5.7

Quote:
Originally Posted by Frango100 View Post
Lets wait for the screenshot then. The upstream sensors are the ones which should give the fuel trim values (so 1-1 and 2-1 sensors), which seems to be fine in what you wrote down.
The downstream sensors (1-2 and 2-2) are used for catalist monitoring and should not give any fuel trim figures.
Here you go. This is the % readout
imgur: the simple image sharer

This is the the voltage graph
imgur: the simple image sharer

In both instances 1x2 & 2x2 seem way off the charts, they never move.

1x1 & 2x2 however are constantly bouncing back and forth from 0 to 9 (never saw a double digit on those yet)

What do you guys think?
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Old 09-04-2014, 02:51 PM
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Re: new to this forum problems with 07 5.7

The 1-1 and 2-1 sensors ( both upstream from cat) should bounce up and down from 0.2V to 0.8V. This shows that the PCM is trying to get the fuel air ratio as close as possible to 1 / 14.7 by constantly adding and reducing fuel to the standard fuel MAP. The fuel trim figures for the 1-1 and 2-1 are normal as well.
The down stream sensors (1-2 and 2-2) should show a steady indication. The cats should burn any remaining fuel particles and uses almost all O2 from the gasses to do so, so the after cat sensors should see a very low O2 content and therefore show a high O2 voltage. Because the low O2 level is quite constant, the O2 sensor voltage will be as well. So again normal indication.
I donīt know why Torque is showing a fuel trim figure for the after cat sensors, since these sensors are not used for fuel trimming purposes. They only serve for monitoring the catalist performance. When the cat its performance goes down, less O2 will be burned and more O2 will be left over at the after cat sensor(s). The O2 voltage will go down with decreasing performance of the cat. So with a rising O2 level in the gasses, the performance of the cat can be measured. There is a certain treshold set in the PCM, whereafter the PCM will trigger the "check engine" light and set a DTC for low cat performance.
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Old 09-04-2014, 03:06 PM
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Re: new to this forum problems with 07 5.7

Thank you. So it seems as though my O2 sensors are in good order. I should be getting my new exhaust Saturday so I will have the installed look very deeply for a leak. I suspect the metal to metal connection right before the muffler. But I will have them check the whole system including the manifold bolts.

Thanks for your help.
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