Jeep Garage  - Jeep Forum banner
21 - 26 of 26 Posts

·
Premium Member
Joined
·
3,465 Posts
***DO NOT BY A JEEP GRAND CHEROKEE 5.7L***

I can not believe the performance of this vehicle. The so called "fish bite" issue with this vehicle is horrible. The vehicle sputters and tugs while driving between 35 and 65 miles per hour. I have had it in the shop three times for the same fish bite issue and everybody starts out denying the issue until you push and prod them into admitting that this problem has been known for a long time now. Chrysler, it seems, has promised a fix for the problem for a year now. They originally told me by August 2013 and as of Sept. 27 still nothing.

It is hard to believe that Chrysler treats customers this way. If you are considering buying a new JGC, I strongly recommend against it. I asked if the new 2014 was any better with the new 8 speed transmission and the service manager told me it was actually worse than the 2013.
I'm glad you found the Jeep Garage. It's refreshing to see someone who's first post is a slam of the product, followed by inaccurate information. :rolleyes:
 
  • Like
Reactions: Willx

·
Registered
Joined
·
1,978 Posts
Interesting, I have not seen anyone with this concern on the 2014s at all. Trust me we see every problem imaginable... Anyone here have this issue with a 2014?

Yoma, also just a quick question, have you tried running mid-grade fuel for a while in your Hemi? I have the 2011 Durango with this problem I ran premium for a while then switch back to Mid-grade and it is much better. To my knowledge if you have a 2012 or 2013, there is still a fix coming. The updates are always late but ask anyone with the 2014s, reported problems have been seeing updates and resolutions.... Again never heard of this on a 2014.
I have no complaints about the drivetrain on my 2014 Summit V8. Way more responsive than my previous 2012 Overland V8.
 

·
Registered
Joined
·
111 Posts
Yoma, also just a quick question, have you tried running mid-grade fuel for a while in your Hemi? I have the 2011 Durango with this problem I ran premium for a while then switch back to Mid-grade and it is much better.
I haven't had to dig in to any problems on a Hemi (haven't owned one - yet), but modern engine computers usually store information about how they're running and adapt to what you feed them. The behavior you saw could have been from needing to let the computer "learn" that you were giving it higher-octane gas so the higher the octane the faster it learned. If so, you could probably shortcut that process by clearing its memory or forcing it in to quick-learn mode.
 

·
Premium Member
Joined
·
4,989 Posts
I haven't had to dig in to any problems on a Hemi (haven't owned one - yet), but modern engine computers usually store information about how they're running and adapt to what you feed them. The behavior you saw could have been from needing to let the computer "learn" that you were giving it higher-octane gas so the higher the octane the faster it learned. If so, you could probably shortcut that process by clearing its memory or forcing it in to quick-learn mode.
There is actually a published Star Case on the issue. Padgett is pretty close on the problem but it could be corrected with a programming update.
 

·
Registered
Joined
·
1,901 Posts
Only way to fix with a computer would be to richen the mixture and back off the timing a bit, both of which would impact MPG and possibly emissions.

The fact that the hemi needs two plugs per cyl firing at different times is an indicator because that is Not Cheap. Makes me wonder if the semi-unique "fishbite" is when the first plug misfires and all combustion if from the second, both at the wrong time and the wrong place.

Since I have a more modern engine, am essentially just making a few guesses. Hemi Engine Plugs Photo 3 has some good pictures of the head and suggests the old Chevvy trick for the straight plug small block heads (slant plug design reduced the need) of indexing the plugs to aim at the exhaust valve (hottest part of the cyl).

Ideally the spark would originate at the peak of the chamber but the key is in the piston design. Normally a design like this would make me wonder if there were really two small chambers formed by the quench but then you would need simultaneous firing not sequential (kinda like a twingle). Pictures on that site of a piston with a hemi-shaped recess does not support this though.

But apparently that is not what is happening "[using] dual fired plugs on each cylinder allows the firing to take place closer to top dead center, and then again when the piston is on the back side of the power stroke.” (from The new Dodge Hemi V8 engine in full detail - 5.7, SRT8 6.1, and 392 6.4 )

The result is a chamber with the initial firing over on the side instead of the center and secondary ignition (later) on the other side sort of like an inexpensive but very slow MSD.

Now on a Buick 3800, when the secondary ignition breaks down in lockup, the effect is pretty violent both in shake and loss of power. Possibly the second plug firing 90 degrees later ("Each cylinder shares a coil pack with another cylinder. Each of the two plugs on a given cylinder is fired by a separate coil") even though very much retarded, reduces the effect to a "fish bite".

The real answer would be a four valve design with a center plug but then the only "Hemi" would be the piston recess.

Sorry, when I get started, it is hard to stop,
 
21 - 26 of 26 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top