3.7L Performance

[K9JEEP]

As of now driving in LA and barley seeing the highway I'm getting pretty bad gas mileage. I barely got over 200 miles on this last tank. A lot of it is driving style as I am so used to my GTI with a 6 speed dual clutch. But even with it heavily modded and protuned at 22psi I can bang on it all day and still get 26-27mpg in the city and 30+ on the highway. I have been getting better with this 4 speed and trying to coast it more light to light and not be so heavy on the throttle

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[HoosierJeeper]

That's just under 10 MPG...that's pretty low even for one of these. I get between 13 and 14 in town, no highway driving and that's with shit in my sig and a ski rack.
Have you done spark plugs? I got about 2 mpg back from running Techron cleaner in mine.

 

[K9JEEP]

I started that thread regarding the CEL issue I was having with misfire on cylinder 4. I have ran Techron through, changed all spark plugs with OE NGK, Changed oil, ran seafoam in gas, crank case and brake booster hose. It runs great but still has that annoying shake at idle. I think I can do better on this tank, this is literally LA city driving. After replacing the number 4 injector the CEL has not came back on in over a week. I do agree that my mileage is super low so I am hoping it will get better and there isn't something I am missing here, again I only have 38k miles on mine.

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[tjkj2002]

That's just under 10 MPG...that's pretty low even for one of these. I get between 13 and 14 in town, no highway driving and that's with shit in my sig and a ski rack.
Have you done spark plugs? I got about 2 mpg back from running Techron cleaner in mine.

What you talking about? Mine get's like 5mpg's city,8-9mpg's when still IFS.

Bigger city driving will always net low mpg's in a 4000lbs+ brick doing a drag race to the next stop light.

 

[K9JEEP]

I also only got 215 miles on the last tank but I don't believe it was all the way full nor was it empty either when I refilled.
LOL I hope I do better than 5mpg. I am in the works of getting rid of my GTI so these MPG are new to me

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[LibertyTC]

Slight shake at idle cold= is pretty much normal for an odd fire v-6.
Mine does not shake after full tune up Hot. Are you running a full synthetic 5w-30 oil?
Did you add 2 bottles of chevron Techron to a tank and hwy drive it for a few hours?
Could try some MMO in the fuel on the next hwy run too.
In town I drive OD off and give er, blows the dust out.
I've given up worrying about fuel consumption, just enjoy driving the Jeep!
58607[/ATTACH]"]

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[HoosierJeeper]

I started that thread regarding the CEL issue I was having with misfire on cylinder 4. I have ran Techron through, changed all spark plugs with OE NGK, Changed oil, ran seafoam in gas, crank case and brake booster hose. It runs great but still has that annoying shake at idle. I think I can do better on this tank, this is literally LA city driving. After replacing the number 4 injector the CEL has not came back on in over a week. I do agree that my mileage is super low so I am hoping it will get better and there isn't something I am missing here, again I only have 38k miles on mine.

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Maybe you have a sticking caliper or something? Wouldn't be surprised with how much it sat.

What you talking about? Mine get's like 5mpg's city,8-9mpg's when still IFS.

Bigger city driving will always net low mpg's in a 4000lbs+ brick doing a drag race to the next stop light.

Well you also carry a full Snap on truck's worth of tools in the back (if I remember a pic from a long time ago), so I would agree that your MPG is normal for a Snap on truck racing from stop light to stoplight :gr_grin::winner_third_h4h:

 

[K9JEEP]

Slight shake at idle cold= is pretty much normal for an odd fire v-6.
Mine does not shake after full tune up Hot. Are you running a full synthetic 5w-30 oil?
Did you add 2 bottles of chevron Techron to a tank and hwy drive it for a few hours?
Could try some MMO in the fuel on the next hwy run too.
In town I drive OD off and give er, blows the dust out.
I've given up worrying about fuel consumption, just enjoy driving the Jeep!
[ATTACH=full]58609[/ATTACH]

Does not shake on cold start, only shakes at idle which is 550-600rpm, I can feel it in the pedals, steering wheel, my seat. Drives smooth and has power once out of idle. I had the service manager sit in it and tell me it feels normal and he has had 2 KJ's before. I feel there should be a shake but I am not sure I should be feeling it in my seat.

I added 1 bottle of Techron through the first tank of gas. Then I did seafoam through the second and now I'm on the 3rd. I was going to try MMO on the next. I changed the oil with Mobil 1 5-20 and mobile filter. I do think it's because of the odd fire as the engine doesn't sound to be missing during idle, if I give it the lightest throttle it goes away, I was thinking it could be a worn engine mount but they don't look to be bad and I would think I would feel it when driving as well if it was.

I thought about the stuck caliper but wouldn't my rotors be toast if it was? I can pull the caliper off and see what it looks like. I did have a brake job planned in the near future. Of course when I had the dealership do the ****** service they called and gave me the old "your brakes look rusty, do you want us to change them?" I've looked at them and they seem fine. I have done full big brake kit upgrades myself so I understand the system but i have never dealt with a stuck caliper.

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[HoosierJeeper]

See if one wheel has more brake dust than another, that's how I found mine.

 

[LibertyTC]

Take a video of the shake at idle would like to see how bad it is.
At the same time it would be nice to have it connected to a Snap on Ultra scanner and see if it is actually misfiring at idle.
The scanner will show counts and on what cylinder and often low counts don't tun on engine light.
Ya sometime I think the shake is also caused by too low of an idle.
Would be nice to turn idle up a notch. I don't think that is even possible.
As the KJ tank is close to 20 gallons, 2 bottles of Chevron Concentrate is required for best results.
Mobil1 "extended performance" is true full synthetic engine oil. I use Penzoil Platinum which also is full syn.
Use a heavy dose of MMO in the gas and techron, a high octane, and take it for a good long hwy drive.
Brake dust is good check, & If a caliper is sticking another hint is the excessive heat/temperature produced compared to other wheels.

 

[JeepinJarhead03]

Good suggestion, though it won't make it shake at idle, does increase drag, the top caliper sliders have a rubber bushing that if grease is used, non synthetic slider grease, they will swell and stick the top caliper slider which wears the inside pad and drags the brakes a certain extent

I just did a complete overhaul of my front end, and my top sliders were stuck so bad i had to vice them and use a hydrolic ram to get them out, can tell a big difference in rolling resistance even with brand new pads that haven't seated in fully that i can only attribute to the brakes not dragging

 

[JasonJ]

I know I get the pleasure of changing said plugs on a daily basis.

Try a F-body Camaro,those back 2 plugs will make you want to never buy a GM product again(really doesn't take much for that decision though) and beat the engineer to death.

Been there, done that! Last favor I ever do for an F-body owner! It was absolutely ridiculous. Same things going on with my FIL's 2001 Tahoe with the 5.3l. Those back two plugs require some sort of voodoo magic to mystically remove the plugs without smashing and scraping your hands to hell. And don't even get me started on the hard brake lines along the frame rail!

By comparison, my Jeep and all the Ford's I've ever owned were cake to work on (waiting for jokes about how much practice I got because they were a Ford product.... lol).

 

[wheeee32]

Been there, done that! Last favor I ever do for an F-body owner! It was absolutely ridiculous. Same things going on with my FIL's 2001 Tahoe with the 5.3l. Those back two plugs require some sort of voodoo magic to mystically remove the plugs without smashing and scraping your hands to hell. And don't even get me started on the hard brake lines along the frame rail!

By comparison, my Jeep and all the Ford's I've ever owned were cake to work on (waiting for jokes about how much practice I got because they were a Ford product.... lol).

The 2 Ford's I owned were really good to me. My 89 F-150 didn't need major work until 200K(fuel switching issue). 2000 Focus HB was a champ till I traded for the KJ.

 

[tommudd]

Been there, done that! Last favor I ever do for an F-body owner! It was absolutely ridiculous. Same things going on with my FIL's 2001 Tahoe with the 5.3l. Those back two plugs require some sort of voodoo magic to mystically remove the plugs without smashing and scraping your hands to hell. And don't even get me started on the hard brake lines along the frame rail!

By comparison, my Jeep and all the Ford's I've ever owned were cake to work on (waiting for jokes about how much practice I got because they were a Ford product.... lol).

Don't know about all Ford's , my 69 Mustang with a 390 was a bear to change plugs in. Worked in a Ford dealership in another lifetime, there were quite a few that were a real bit**. Of course you did say " I've ever owned"

 

[JasonJ]

Don't know about all Ford's , my 69 Mustang with a 390 was a bear to change plugs in. Worked in a Ford dealership in another lifetime, there were quite a few that were a real bit**. Of course you did say " I've ever owned"

True..

I always enjoyed working on the Ford's that I had... none were too difficult or required much beyond basic maintenance and wear parts replacement.

My wife's Acadia is thus far the worse vehicle I've owned for spark plug replacement...

 

[HoosierJeeper]

I'm not looking forward to spark plugs on my KL, but they're iridium and Jeep says they're good for 100k. Got 92k miles to figure it out.

The LR3 was actually really easy, maybe easier than the KJ. The XJ looks simple, haven't done them yet, they were fresh when I got it.

 

[tommudd]

I'm not looking forward to spark plugs on my KL, but they're iridium and Jeep says they're good for 100k. Got 92k miles to figure it out.

The LR3 was actually really easy, maybe easier than the KJ. The XJ looks simple, haven't done them yet, they were fresh when I got it.

Yes the XJs are super simple, between them and a KJ not sude which is easier . Well if we didn't have 6 nuts to remove as well

 

[ltd02]

Good suggestion, though it won't make it shake at idle, does increase drag, the top caliper sliders have a rubber bushing that if grease is used, non synthetic slider grease, they will swell and stick the top caliper slider which wears the inside pad and drags the brakes a certain extent

I just did a complete overhaul of my front end, and my top sliders were stuck so bad i had to vice them and use a hydrolic ram to get them out, can tell a big difference in rolling resistance even with brand new pads that haven't seated in fully that i can only attribute to the brakes not dragging

My sliders got gummed up like that. I just took the goofy bushing off and never felt or heard a difference. I change the sliders with every brake job and the next time I did the fronts I didn't even bother putting the bushing in. Thought they were supposed to stop some rattle. I couldn't tell but I'm half deaf anyway.

 

[ltd02]

True..

I always enjoyed working on the Ford's that I had... none were too difficult or required much beyond basic maintenance and wear parts replacement.

My wife's Acadia is thus far the worse vehicle I've owned for spark plug replacement...

When the wife's Sienna need plugs at 100k I took one look and told her to take it to the dealer. The 400ish bucks was well worth it to me. Now at about 220k I guess it needs it again.

I'm a big Ford fan although I only have one out of the too many vehicles I have right now. Had some good GMs back in the day but the last one I had about 10 years ago pretty much ruled out me ever getting another. :favorites68:

 

[K9JEEP]

Agree the brake issue wouldn't cause the shake at idle but I will get around to refreshing the the braking system.

I also agree that the shake is due to a low idle, because on a cold start it does not do it, even when getting down to 750ish RPM, the shake occurs when it drops down below 600
This is my idle RPM

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