I do know that the 3.8 is not the most powerful of motors, and that I am drive a jeep, not a sports car, nor is it a hauling truck. I am pulling a trailer that loaded weighs about 1400 pounds total. All my mod's are in my signature.



We made it from Indiana to Pueblo, Co. without any issues at all. Filled up there and set out for Durango. That is when problems started. Jumping a lot in and out of gears (automatic) and the throttle peddle would sometimes not even respond at all ( push it down and nothing would happen). My wife was driving at the time, and she quickly said NO MORE, your turn! From their I got us to Alamosa for the night. I was thinking that maybe we got bad fuel in Pueblo, so I used extra fuel to see if that would make any difference. (As things went, I would say that it didn't make a difference).

The next morning we set out for Mesa Verdi, things seemed okay, kinda. But once we started up Wolf Creek pass, things went to hell quick. Before we made it to the top, I was in first gear (automatic) at about 25'ish mph and I had it to the floor, and I was loosing it fast! We stopped at the overlook at the top to rest the Jk, and I thought I probably smoked the trany! I check the fluid, looked good, smelled right to me too. After a fair amount of cooling down time, we continued on our way. At Durango, I stopped at a repair center, and explained the problems that I was having and had them look and smell the trany fluid. They said it was not burnt, but that the pass is very difficult and if there is a problem with the vehicle, that that would be the place to have trouble! They wanted to hook it up to the computer, but couldn't get to that until later in the afternoon sometime.

We decided to take a break, lunch and head on to Mesa Verdi. Things went okay, and we where still on schedule. I unhooked the trailer for the afternoon. I thought I would see how it went without the trailer, thinking that it was the real problem. Well it was not the real problem, might have added to it, but it was not all the trailers fault. The jeep was having trouble with the grades in the park itself.

Now it was time, the decision was obvious, time to take it to the dealer in Cortez, plan for the worst, rent a vehicle if we have too, and finish the trip, who knows. So in the morning, we head to the dealer in Cortez. I set my Superchips back to stock, it was setup for 91 oct. performance (best setting that I have found for me), and then to the dealer to explain my problems. They were nice to deal with and were willing to get me in asap. Well asap was a couple of hours later, but that's okay, it was hot and boring, my wife and kids got a ride to Walmart to do some shopping, I just waited.

Once they drove it, they hooked it up to the computer, and the worst thing happened, kinda. They found nothing. Not a single code! Now I was starting to wonder if the Superchips, when reset back to stock, might have done something to it, but I don't think so, or they would have had nothing to really look at in their read out, and I think they would have had a lot of question for me about that. They flashed the computer, as they said, "several times" and the did 2 different recall updates. Not sure what they were, didn't get a real answer, just some code numbers. The mechanic said something like "never like the 3.8, its a dog and you'll have to live with it. So about 3.5 hours from the start, nothing found, and 90 dollars spent diagnostics. I was not very happy when I left, but I was grateful not to have repairs to wait on.

I left the dealer, and on my way to get my wife & kids at Walmart, I stopped and reset things with my Superchips ( tire size, gears and back to 91 oct. performance ). Then we started our trip to Page. And on the way, things didn't go okay, they went really good. Never had the throttle pedal not respond, didn't seem to want to jump around near as much for gears, it was more like when we started the trip.

We did continue our trip with stops at North Rim, Zion NP, Bryce Np, and then on to Moab. Not any real issues at all anymore. Did several trails in Moab, no trailer of course, and we had a blast.

Now we had one last obstacle to get past, Vail Pass. I wasn't sure how it would do, but it did great. I was running about 50 mph up it, passing for the first time, semis and other slower vehicles with trailers. I think I would have made it all the way like that, but I got cut off by a vehicle, and it put me behind a semi that was doing about 30 mph. I did pass him, but I never regained my speed that I had before that. Not the Jeeps fault, it was a tough climb for a lot of vehicles with trailers.

The rest of the trip home was uneventful. With no real grades, it pulled much like when we left for our trip and my wife commented, "you can't even tell there is a trailer back there".

It would seem to me, that when the dealer reset the computer, that it did change something. Or that I might have been able to fix my own problem by using my Superchips, setting it to stock and the resetting it back to my settings again. I don't know, and maybe never will.

There is one thing I do know. If I plan another trip like this, it will be with a Hemi, supercharger, or something. The 3.8 is underpowered for real world highway driving will pulling even as light a load as I had. It's good as grocery getter, and really good off road, and in 4 low. But I need to be able to get to the trails too!

 

Firstly, glad you don't have any repairs to do.

Flashing the computer back to stock probably erased any codes if you did have any, though they should have shown up during the flashing process (the programmer should tell you if you have any codes).

As for performing better afterwards, I had a similar experience a few weeks ago. I had to disco my battery for a couple hours while doing some wiring under the hood, and the Jeep felt peppier for a few days after. FYI I have the Procomp/Hypertech on 87.

EDIT: Didn't finish my thought process: while the computer is "learning" it probably reverts to a program with more fuel added.

I think it may be that the JK is programmed from the factory to run lean. This is for emissions and mileage. Even with the aftermarket programs, they still run on the lean side. Thus there's some horsepower being left on the table because they're not running the most efficient air/fuel ratio. Yes, running slightly lean is good when cruising, but you want to run slightly rich when under load to give every oxygen molecule a chance to burn as well as cool the cylinders a bit with unburned fuel. This is also why many members are experiencing spark knock both with and without programmers.

If I could put any motor in the JK, I'd pick one with good all around performance but also efficiency, economy, and a wide torque band. Some of the best motors out for that are the Audi direct injection V6s, or maybe the Ford Ecoboost V6.

 

Cars generally feel slower at higher altitudes, if that makes sense. I definitely notice a difference now that I live in Colorado -- my Jeep, and the truck that I had before the Jeep, generally feel less responsive and feel like they have less power than they do at 'normal' elevations.

 

with your superchips and towing a trailer, why don't you try the "towing" tune?

 

Before my big trip, I pulled the trailer all over the place for several weeks, sometimes with a load and sometimes empty. I tried several settings, and 91 setting was the best setting for mpg and power. The tow setting was much less in mpg and was a little harsh with its gear shifts.

That being said, I didn't want to test it out at high altitudes, or extremely long grades. Maybe I should have , but after the resetting at the dealer, and things improving from there on, I was to happy and relieved to experiment. Besides, I think my wife would have killed me if I fiddle with things and caused it to mess up again!

Added note I just finished calculating my Mpg for the trip.

4450 miles round trip ( this is all miles drive which includes trails that might have used 4 low)

15.20 mpg

.2025 cents per mile

Ability to take my family out west= PRICELESS

 

My wife would not drive the Jeep any distance just because of that. She did not even like to be the passenger. So after one more long trip, she told me to get the HEMI.

 

Did you shut the overdrive off when pulling hills? Also are you thinking of installing a good tranny cooler? I was thinking that your gas mileage wasn't too bad. Nice trailer! Looking forward to your Hemi build thread!

 

I ran with the overdrive on up until the Colorado border and then turned it off. And then never really turned it back on until sometime after Denver when there were no more grades to really deal with.

Of course you have to do it every time you start the vehicle. Which I just don't understand at all. Its an off road vehicle, I don't know about all of you, but I don't 4 wheel in overdrive.

I did add a tranny cooler 2 weeks before we left for our trip west. I read somewhere here that they have trouble with over heating. I did receive a recall notice from Chrysler 2 days before we left, but could not take it in time to start our trip. Will look into that now, but if it is just a computer update, that might have been one of the recall updates that the dealer on our trip did. Need to find my paper work from the dealer to find out.

I have to say that I am pretty happy with my MPG. It was really close to what I had estimated for the trip.

Glad you like the trailer! I built it especially for this trip. It was one of the most enjoyable winter projects that I have done in a really long time. As my wife said to me on our trip out, "you can't even tell we are pull a trailer".

 

Yup, your mpg was good.

And yes, part of your power loss was due to the altitude, as much as 30% through some of the high passes.

As for the overdrive button, not many vehicles keep the O/D off on restart. And when you're offroading, you probably don't get close to O/D anyway. At least I rarely had to turn O/D when I wheeled my auto Exploder.