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Old 12-17-2012, 02:11 AM
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2007 cherokee hemi

GJust got a 07 hemi with 55,000 miles on it. Have a few questions.

How accurate is the computer mpg? I'm not expecting much but I'm only getting 10-11.

This is my winter vehicle (infiniti g35) other vehicle. Wasn't expecting great mpg but its gone down sine July when I bough it. Coming up on 60k maintenance and was wondering will plugs n wires help?

Also.. the jeep has quadra drive II is that more maintenance will it help come snow vs the other options jeep offered?

Intake options n gains? Cost?
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Old 12-17-2012, 06:42 AM
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Re: 2007 cherokee hemi

Welcome to JeepGarage!! With all your questions, you would be best to post something in the WK section of the forums to some answers.
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Old 12-19-2012, 07:43 PM
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Re: 2007 cherokee hemi

The computer calculated mpg is fairly precise, at least in my experience, but it may vary across all of these vehicles. Plugs and wires may help, but you may also want to check numerous other parts, including PCV valve, MAP sensor and EGR valve. Some recommend a Seafoam treatment, but I generally stay away from anything advertised as a "mechanic in a can". However, carbon build up appears to be pretty severe in these models. Try searching the forum for "catch can" and the pictures will tell their own tale. The QDII does not require any more maintenance than regular 4x4 vehicles, but I would recommend you get all fluids changed, including transmission, transfer case, differentials and coolant. Oh, and don't forget the oil The QDII should be fairly efficient in snow, but it all comes down to tires and your ability to drive in that type of weather. 4 wheel drive is no guarantee that you will make it to your destination and it should never give you a sense of over-confidence. Plenty of ignorant drivers overestimate the ability of their vehicles and their own skills - just take a look at the number of traffic accident once the first snow falls. In terms of intake and other mods, many recommend a Cold Air Intake (CAI), but stand alone, a CAI doesn't really do anything for your vehicle in any way. Plus, some of the CAI's are notorious for soaking up moisture in bad weather and thus negating any benefits of a CAI. Either you go all the way (PCM tune, CAI, exhaust/muffler), or be happy with your stock GC, IMO. In the end, even my limited 5.7 Hemi will never be a SRT8, so don't set yourself up for disappointment. So far, my total cost for my upgrades, which include Flowmaster muffler + resonator delete, Predator 91 Oct. tune and an Airaid JR Kit has cost me around ~$600. No real gains in terms of performance according to my butt, but a real dyno tune or custom tune will certainly change that. Are you in a giving mood this Xmas??
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Old 12-19-2012, 08:08 PM
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Re: 2007 cherokee hemi

Sorry but I do not agree with most of the long previous post. SInce the question posted is about mpg, yes it is accurate, and by all means Seafoam will help with 55k, as so many Hemi owners can testify to. MDS lifters will start sticking long before the miles you have and Seafoam frees them up, and it then runs far better. Other fuel system cleaners did nothing in my experience. You also don't need to replace any parts at this point, and if plugs were done at 30k,. they are still fine and you will notice no difference. I would replace the air filter and that should be it for parts. Your throttle body is the big problem, which is all gunked up, and will reduce performance and mpg. The first thing to buy is a catch can, then clean the TB, You can remove and carefully clean it using alcohol and a rag, or just get a new ported TB which is a worthwhile upgrade. EIther way, reset the ECU after doing either. Last, your right foot determines mpg and if you are constantly taking off and braking late, don/t expect to get 14 mpg. Mine gets 22 HWY, 13 city.
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Old 12-19-2012, 11:18 PM
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Re: 2007 cherokee hemi

No offense dmsfun, but the air filter will do absolutely nothing in terms of mpg. Newer vehicles with fuel injection are not affected the same way by dirty air filters as older vehicles without fuel injection. Replacing the air filter is just plain superstition in terms of mpg. Regarding Seafoam treatment, it may work, but it may also cause significant issues with the MAP sensor, for example. But hey, now we know who believes in fairy tales...
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Old 12-20-2012, 10:56 AM
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Re: 2007 cherokee hemi

Since you have never tried Seafoam, your Hemi is all gunked up, has the tick from sticky lifters, and runs like crap, like mine used to. Night and Day improvement in everything after one treatment. If you do not have a catch can, the gunking is going to be severe, and it is guaranteed your Hemi is a total dog. There are no effects on the MAP, all BS. Mine now has 83k , no tick or any noises, and drives better than ever. With the upgrades it is significantly faster, clocked at 0-60 5.2, so yeah, I know what works and what doesnt. Replace the stock panel filter and this is absolutely neccessary, at a cost of 10 bucks. You are only choking the engine by not doing this, worsening mpg and performance. The bottom line is to take advice from those who have tried things and tested them, not people who theorize. For a total of 20 bucks the OP will totally cure all the issues, it will run better than ever, and no other parts are needed.
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Old 12-20-2012, 12:34 PM
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Re: 2007 cherokee hemi

Dmsfun, I am not theorizing here. I am telling the facts.

First off, Jeep recommends all of the maintenance items that I have described (schedule B). Whether you decide to follow those recommendations is up to you. If it was my vehicle, I would do all of those items for several reasons. One being that when the fluids are drained, you have a good chance at getting a direct and tell-tale look into the condition of the vehicle. For example, looking at the lubricants (transmission, transfer case, differentials) and how polluted the lube is when removed may warn of premature wear and future repairs. This can also be done by taking a sample, for example of the transmission fluid, but after 60 K miles, it's a good bet that its time to change the fluid anyways. Of course, if the vehicle recently had these items checked and the fluids replaced, the need to redo them becomes null and void. Have a reputable mechanic evaluate the services needed for your Jeep to make sure you are not performing unnecessary or duplicate repairs. A second reason for following the recommended schedule is in terms of warranty. If you do not follow the recommended schedule, you may find that the manufacturer will not honor the warranty when something breaks. Also, some manufacturers may state that their coverage expires at a given mileage or age of the vehicle, but if you can prove that you have maintained your vehicle in full compliance with the manufacturer's recommended service schedule, they may cut you a break on repairs, or cover the repairs completely, even after the warranty has expired. However, I seriously doubt that is the case with Chrysler, but other high end manufactures may. I have seen this happen before and have personally handled these types of warranty claims with good success. Saving $50-100 on fluids versys a new transmission or transfer case is in my opinion a really poor investment.

Admittedly, I am not a mechanical engineer, nor do I hold a degree in an equivalent area. However, I have worked for several large automotive and motorcycle manufacturers, including BMW, Suzuki and a few others. I have worked both in sales, service and administration. Working around people, who are at a Master Tech level, engineering and design specialists, will sometimes entail the benefit of gaining some insights that you may otherwise not have the opportunity to learn. If you think I am lying or embellishing my knowledge, you can try and do some research yourself. At a quick glance, here are a couple of articles that describe the exact effect, or lack thereof, of dirty air filters in terms of mpg:

http://www.fueleconomy.gov/feg/maintain.shtml

Myths on raising gas mileage - Los Angeles Times

http://www.consumerreports.org/cro/m...yths/index.htm

Because newer vehicles equipped with fuel injection, including the '07 GC, mostly run a closed loop control circuit in the ECU, the only thing a dirty filter will do is to rob you off a few horses. There is no real noticeable effect of a dirty air filter on gas mileage, but there may be on performance and output, depending on the severity.

Look, you can do whatever you want with your car and in the end, you will be the one responsible for what you end up getting into. But in my book, when someone tells you it is "just an easy fix" and "I have tried this at home", a really big red warning flag goes up in my book. Obviously, Dmsfun has had some success with his Seafoam treatment(s), but to recommend that and an air filter replacement as a substitute for a 60K service is nothing less than pure ignorance. That much should be obvious to even the most inexperienced reader. And had dmsfun read the instructions on the Seafoam can before he used it, he would see that it clearly states NOT to use Seafoam anywhere near the MAP sensor.

Good luck to both of you!
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Old 12-23-2012, 11:14 AM
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Re: 2007 cherokee hemi

Winter fuel will show a decrease im mpg from july. Longer warmup time also.
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Old 12-24-2012, 05:55 AM
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Re: 2007 cherokee hemi

Keep in mind that the time the jeep is idling factors into the EVICs MPG calculations. If I remote start mine the MPG goes down significantly.
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Old 12-25-2012, 05:38 PM
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Re: 2007 cherokee hemi

Quote:
Originally Posted by bizz518 View Post
GJust got a 07 hemi with 55,000 miles on it. Have a few questions.

How accurate is the computer mpg? I'm not expecting much but I'm only getting 10-11.

This is my winter vehicle (infiniti g35) other vehicle. Wasn't expecting great mpg but its gone down sine July when I bough it. Coming up on 60k maintenance and was wondering will plugs n wires help?

Also.. the jeep has quadra drive II is that more maintenance will it help come snow vs the other options jeep offered?

Intake options n gains? Cost?
Several other opinions posted here....so I'll offer mine. This my 4th Jeep GC, so I'm not fresh off the farm with the egg money.

EVIC mpg's are reasonably accurate....certainly within 1 mpg of the calculator method (using miles travelled and gallons filled) in my expereience of 5+yrs/93K miles of WK ownership.

Your intake is sized to handle air flow at 6K+ rpm and you probably run at less than half that number normally (...mine is 1,900-2,200 rpm on the highway and up to 2,500 rpm in town). It's got twice the capacity that you are probably using. My air cleaner box inlet has a cold air intake in front of the radiator support. IAT runs 5-10F above ambient. Do not expect significant gains (except intake noise) from a whole new CAI system.

One of the things I had to do to maintain my powertrain warranty is show the dealer that the required maintenance tasks had been completed within the specified schedule (mileage/time). I was able to do so and retained the warranty coverage until the next inspection.

It turns out that I exceed the service requirements by at least a small margin in all cases. As stated previously, I like to look at the condition of the drained lubricants and removed parts. With the exception of worn rear brake pads and rotors, everything else I replaced has been ready for changeout, but otherwise unremarkable. Of course, this does not include parts that failed prematurely and needed replacement under warranty provisions.

I know that many have touted the benefits of Seafoam treatment. I'm not sure either way. However, I do know that it has to go in your oil pan to affect the MDS lifters and in the intake manifold to affect the MAP sensor. MAP sensor is ~$25. I just changed it. Only 1 person has reported complete cure of the HEMI tick by Seafoam. I'll wait-and-see for now.
The part about Seafoam that concerns me is that whatever burns off goes past the O2 sensors and through the catalytic converters. It may also plate out on the spark plugs. I've had O2 sensor issues (3 complete sets) and cats replaced due to early failure. Leary of adding any more potential problems.
I guess you might do the Seafoam, then plan to replace the plugs. and MAP sensor. (.....and O2 sensors if DTC's pop up). However, I wouldn't do it at the expense of other scheduled preventive maintenance tasks.

That's my story and I'm sticking to it. CAUTION: This opinion may be worth what you paid to get it.
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Old 12-27-2012, 11:29 AM
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Re: 2007 cherokee hemi

Quote:
Originally Posted by WK2007 View Post
Dmsfun, I am not theorizing here. I am telling the facts.

First off, Jeep recommends all of the maintenance items that I have described (schedule B). Whether you decide to follow those recommendations is up to you. If it was my vehicle, I would do all of those items for several reasons. One being that when the fluids are drained, you have a good chance at getting a direct and tell-tale look into the condition of the vehicle. For example, looking at the lubricants (transmission, transfer case, differentials) and how polluted the lube is when removed may warn of premature wear and future repairs. This can also be done by taking a sample, for example of the transmission fluid, but after 60 K miles, it's a good bet that its time to change the fluid anyways. Of course, if the vehicle recently had these items checked and the fluids replaced, the need to redo them becomes null and void. Have a reputable mechanic evaluate the services needed for your Jeep to make sure you are not performing unnecessary or duplicate repairs. A second reason for following the recommended schedule is in terms of warranty. If you do not follow the recommended schedule, you may find that the manufacturer will not honor the warranty when something breaks. Also, some manufacturers may state that their coverage expires at a given mileage or age of the vehicle, but if you can prove that you have maintained your vehicle in full compliance with the manufacturer's recommended service schedule, they may cut you a break on repairs, or cover the repairs completely, even after the warranty has expired. However, I seriously doubt that is the case with Chrysler, but other high end manufactures may. I have seen this happen before and have personally handled these types of warranty claims with good success. Saving $50-100 on fluids versys a new transmission or transfer case is in my opinion a really poor investment.

Admittedly, I am not a mechanical engineer, nor do I hold a degree in an equivalent area. However, I have worked for several large automotive and motorcycle manufacturers, including BMW, Suzuki and a few others. I have worked both in sales, service and administration. Working around people, who are at a Master Tech level, engineering and design specialists, will sometimes entail the benefit of gaining some insights that you may otherwise not have the opportunity to learn. If you think I am lying or embellishing my knowledge, you can try and do some research yourself. At a quick glance, here are a couple of articles that describe the exact effect, or lack thereof, of dirty air filters in terms of mpg:

Gas Mileage Tips - Keeping Your Vehicle in Shape

Myths on raising gas mileage - Los Angeles Times

Fuel Myths | Tips for Saving Gas - Consumer Reports

Because newer vehicles equipped with fuel injection, including the '07 GC, mostly run a closed loop control circuit in the ECU, the only thing a dirty filter will do is to rob you off a few horses. There is no real noticeable effect of a dirty air filter on gas mileage, but there may be on performance and output, depending on the severity.

Look, you can do whatever you want with your car and in the end, you will be the one responsible for what you end up getting into. But in my book, when someone tells you it is "just an easy fix" and "I have tried this at home", a really big red warning flag goes up in my book. Obviously, Dmsfun has had some success with his Seafoam treatment(s), but to recommend that and an air filter replacement as a substitute for a 60K service is nothing less than pure ignorance. That much should be obvious to even the most inexperienced reader. And had dmsfun read the instructions on the Seafoam can before he used it, he would see that it clearly states NOT to use Seafoam anywhere near the MAP sensor.

Good luck to both of you!

Pure ignorance, LOL., he does not have 60k yet, so spending money to do 60k service before it is due will do nothing to make it run any better. MAP, PCV, etc are also not part of 60k. Theorize all you want. but the bottom line is since you have not used Seafoam, your opinion is totally useless. It is also 100 percent certain you have the Hemi tick from the lifters sticking, and it runs like a dog, like mine did before Seafoam. One bottle is 8 bucks, and mine immediatley woke up, ran much smoother, and mpg increased notably.
I've also had a CC intalled, and am meticulous with maint, only ran top tier 89 Oct, injector cleaners, etc and it still ran like crap compared to after 1 seafoam treatment. Mine now runs like a bat outa hell after useful power adder upgrades.
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Old 12-28-2012, 07:38 PM
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Re: 2007 cherokee hemi

Quote:
Originally Posted by dmsfun View Post
...he does not have 60k yet, so spending money to do 60k service before it is due will do nothing to make it run any better. MAP, PCV, etc are also not part of 60k.....
I've also had a CC intalled, and am meticulous with maint, only ran top tier 89 Oct, injector cleaners, etc and it still ran like crap compared to after 1 seafoam treatment. Mine now runs like a bat outa hell after useful power adder upgrades.
1. PCV valve is due ~60K miles. May look OK and rattle, but the spring is probably weak by then. OP should add oil catch can at the same time. My BT oil catch can pulls lots of oil vapor/condensed liquid out of the suction stream.
2. You are correct that the MAP sensor does not have a specified changeout interval. However, mine was totally gunked up (a technical engineering term) at 45K miles and probably affected the flexibility of the silicone diaphragm and piezoelectric sensor. The MAP sensor is a primary input for a number of PCM parameter calculations so its proper functionality is important.
My EGR valve was also misbehaving at the same time. It was changed and now performs properly.
I monitor EGR position and EGR error, MAP, spark advance, and load underway. These are all normal with the new components (changed at 40-55K miles on the odometer).
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