Please help! I'm mid-roadtrip. Loss of power and mpg - JeepForum.com
 
LinkBack Thread Tools
post #1 of 15 Old 07-10-2020, 07:10 PM Thread Starter
dahatchh2
Registered User
 
Join Date: Jul 2020
Posts: 8
Please help! I'm mid-roadtrip. Loss of power and mpg

I have a 2012 Jeep Grand Cherokee Laredo 5.7 L Hemi
I am in the middle of a massive road trip and my Jeep has started to have some troubles. All of the repair shops around here are booked out to the next week, so taking my Jeep in isn't really an option at this point. I put about 1200 miles on my vehicle since this problem started. My Jeep hasn't died yet, but I'm starting to get pretty worried, as it's slowly getting worse. Any thoughts or help would be thoroughly amazing!

I've noticed that my Jeep has a huge loss in power, especially under 2,500 RPM. It almost has nothing to give under 2,500. Once I get to about 2500 rpm, it seems to accelerate just fine. Up to that point though, it can maintain speed, but can't accelerate at all. It has to downshift in order to accelerate. It is like this throughout the whole range of gears. Also, even on tiny Hills, it decelerates. On big hill that make sense, but this thing has got a Hemi in it, and small hills did not use the phase this thing at all.
It has also dropped MGP significantly. I used to get 20 to 22 MPG Highway no problem. Now I am only getting 15 to 16 MPG. This is while averaging 65 mph

Since this problem has started, I have change the oil/oil filter, air filter, and put in new spark plugs.
There is no CEL on and everything sounds fine a normal

dahatchh2 is offline  
Sponsored Links
Advertisement
 
post #2 of 15 Old 07-10-2020, 08:20 PM
ColdCase
My Reality Check Bounced
 
ColdCase's Avatar
2011 WK 
 
Join Date: Sep 2009
Location: New England
Posts: 15,937
Look for vacuum leaks, or a bad brake booster vacuum check valve.

Any brakes hot? They may be dragging.

Check for loose connections or frayed wires.

Shift the transmission manually, use sport mode, keep the rpms above 2500 when you can. Won't help mpg but would be an easier drive.

You could have a sensor going bad, but those usually throw a diagnostic code and CEL.

I was born with nuttin' and I still have most of it
Current: 2011 Grand Cherokee Overland V8, 2009 Liberty Rocky Mt V6
Previous: 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac
ColdCase is offline  
post #3 of 15 Old 07-10-2020, 08:32 PM Thread Starter
dahatchh2
Registered User
 
Join Date: Jul 2020
Posts: 8
I'll have to look into the vacuum leak and the dragging brakes. I'm fairly certain its not dragging brakes.
I have regularly been using manual mode to help with RPM management.
Thanks for the input. Any other ideas would be helpful
dahatchh2 is offline  
 
post #4 of 15 Old 07-11-2020, 06:35 AM
ColdCase
My Reality Check Bounced
 
ColdCase's Avatar
2011 WK 
 
Join Date: Sep 2009
Location: New England
Posts: 15,937
Just about all the other things I can think of would throw a code. Low oil pressure or worn lifter(s) or burned valve may do this kind of thing. But worn lifters are usually noisy.

The booster check valve is a common thing, cheap and easy to replace.

I was born with nuttin' and I still have most of it
Current: 2011 Grand Cherokee Overland V8, 2009 Liberty Rocky Mt V6
Previous: 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac
ColdCase is offline  
post #5 of 15 Old 07-11-2020, 09:21 AM
Mogul
Registered User
 
Join Date: Dec 2011
Location: Colorado Springs
Posts: 64
Fuel filter? Fuel pump?
Mogul is offline  
post #6 of 15 Old 07-11-2020, 02:18 PM
ColdCase
My Reality Check Bounced
 
ColdCase's Avatar
2011 WK 
 
Join Date: Sep 2009
Location: New England
Posts: 15,937
I would think a fuel problem would be a high rpm or stalling problem, unless its bad fuel. There could also be an exhaust restriction or a lazy O2 sensor but those typically affect higher rpms, where vacuum leaks tend to affect low rpm.

Anyway could be lots of things, what can he do easily in a hotel parking lot without proper tools?

I was born with nuttin' and I still have most of it
Current: 2011 Grand Cherokee Overland V8, 2009 Liberty Rocky Mt V6
Previous: 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac
ColdCase is offline  
post #7 of 15 Old 07-12-2020, 09:05 AM Thread Starter
dahatchh2
Registered User
 
Join Date: Jul 2020
Posts: 8
Update...

So I was driving the other day and it finally threw a code "P0305 Cylinder 5 misfire detected"
I re-seated the new spark plugs and replaced the coil. Neither of these fixes helped. Could it be something to do with the injector?
And yes, because I am traveling, I do have limited tools at this point
dahatchh2 is offline  
post #8 of 15 Old 07-12-2020, 09:06 AM Thread Starter
dahatchh2
Registered User
 
Join Date: Jul 2020
Posts: 8
Also, would the brake booster check valve throw a code. I'm assuming an O2 sensor would
dahatchh2 is offline  
post #9 of 15 Old 07-12-2020, 11:43 AM
ColdCase
My Reality Check Bounced
 
ColdCase's Avatar
2011 WK 
 
Join Date: Sep 2009
Location: New England
Posts: 15,937
If other things were checked OK, you need to pull the valve cover and watch the operation of cylinder #5 valves (assuming P0305 is cylinder 5). If they are not opening the same amount as the others, then the lifter is bad. If it gets bad enough, it will ruin the cam. Off hand I’m not sure how to nurse it.

Things like vacuum leaks, weak spark, low fuel pressure typically don’t throw codes until a misfire is detected.

I was born with nuttin' and I still have most of it
Current: 2011 Grand Cherokee Overland V8, 2009 Liberty Rocky Mt V6
Previous: 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac
ColdCase is offline  
post #10 of 15 Old 07-12-2020, 05:05 PM
ColdCase
My Reality Check Bounced
 
ColdCase's Avatar
2011 WK 
 
Join Date: Sep 2009
Location: New England
Posts: 15,937
As these kinds of things get worse, the weakest cylinder will start misfiring.

•Corroded PCM power and ground circuits.
•Improper CKP, CMP, MAP and TP sensor mounting.
•Poor connector/terminal to component connection for CKP sensor, CMP sensor, MAP sensor, TP sensor, fuel injector, ignition coil, etc.
•Vacuum leaks.
•Restricted Exhaust system.
•Restricted Air Induction system.
•Overfilled engine oil or transmission

So check these if you can, the air filter could have a mouse nest, for example.

Just about everything else requires some kind of scan tool with live data recording or fuel pressure gauge adapters. Some possibilities:

ASD (auto shut down) OUTPUT CIRCUIT
INJECTOR CONTROL CIRCUIT
COIL CONTROL CIRCUIT
IGNITION WIRE
SPARK PLUG
IGNITION COIL
FUEL PUMP INLET STRAINER PLUGGED
RESTRICTED FUEL SUPPLY LINE
FUEL PUMP MODULE
FUEL PRESSURE LEAK DOWN
FUEL INJECTOR
ENGINE MECHANICAL
POWERTRAIN CONTROL MODULE (PCM)

When a Misfire is detected for a particular cylinder, the PCM will shut down that cylinder's Injector Control circuit.

Misfires detected during a deceleration are indicators of mechanical concerns

I was born with nuttin' and I still have most of it
Current: 2011 Grand Cherokee Overland V8, 2009 Liberty Rocky Mt V6
Previous: 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac
ColdCase is offline  
post #11 of 15 Old 07-13-2020, 06:37 AM
WK2Overland4X4
Registered User
2012 WK 
 
Join Date: Jun 2020
Location: Pittsburgh
Posts: 174
Quote:
Originally Posted by dahatchh2 View Post
So I was driving the other day and it finally threw a code "P0305 Cylinder 5 misfire detected"
I re-seated the new spark plugs and replaced the coil. Neither of these fixes helped. Could it be something to do with the injector?
And yes, because I am traveling, I do have limited tools at this point
Rotate the parts, swap coil/plugs/injectors around and see if the code follows them, doublecheck wiring connectors as well.
If the code moves to another cylinder, you found the problem, if not, wiring or internal problem.
WK2Overland4X4 is offline  
post #12 of 15 Old 07-15-2020, 07:57 PM Thread Starter
dahatchh2
Registered User
 
Join Date: Jul 2020
Posts: 8
It finally got so bad, I had to put an end to my trip. I found a shop in Dayton, Ohio that took a look at my Jeep. They informed me that my cam and lifters are bad. They are asking $7600 to do the work. Sound a little steep to anyone else? I'm going to take a closer look at the costs associated with this.
dahatchh2 is offline  
post #13 of 15 Old 07-15-2020, 08:03 PM
Fast55
Registered User
 
Fast55's Avatar
2017 WK 
 
Join Date: Feb 2014
Location: Ventura County USA
Posts: 514
Garage
You can get a re manufactured long block for half that price. Probably a couple grand more to get it installed. Pass.

2017 Trailhawk
Active Safety, Luxury group, Blind spot detection
Hemi
Rock Rails, Chief Products
Fast55 is offline  
post #14 of 15 Old 07-15-2020, 08:04 PM
ColdCase
My Reality Check Bounced
 
ColdCase's Avatar
2011 WK 
 
Join Date: Sep 2009
Location: New England
Posts: 15,937
Given they are right, a roller lifter seized which then began to ride up on and wear the cam. That requires cam and lifter replacement.

If you let it go far enough it may continue to wear through to the needle bearings which spilled into the engine oil. It then proceeded to chew up the cam shaft all the while spewing metal shards through the engine and effecting other parts.

So best case is cam and lifters, a big job, but not $7000. Worst case its an engine replace kind of job, which could be $7000.

https://www.jeepforum.com/forum/f309...ained-4400427/

I was born with nuttin' and I still have most of it
Current: 2011 Grand Cherokee Overland V8, 2009 Liberty Rocky Mt V6
Previous: 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac
ColdCase is offline  
post #15 of 15 Old 07-15-2020, 08:34 PM
WK2Overland4X4
Registered User
2012 WK 
 
Join Date: Jun 2020
Location: Pittsburgh
Posts: 174
You can get a complete engine/trans dropout with a warranty for half of that, probably installed.
WK2Overland4X4 is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.



Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome