Sure enough, V6 made from a V8. Reviewers describe it as a “lump” because of a lack of smoothness. It fits the tooling to machine it but that doesn’t mean it is the best way to do a V6. If paired cylinders are going to share a crank pin, 60 or 120 degrees is smoother.
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Has your shop already done the 3 most basic misfire tests?
- Swap spark plugs between suspect cylinder and good cylinder? If misfire moves to other cylinder, you’ve got a problematic spark plug.
- Same idea, Swap Coils.
- Same idea, Swap fuel injectors.
Suggest to ask shop to do those 3 tests first, before considering anything else.
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If I saw a mechanic doing that to determine the cause of a misfire I would move him back to the oil change rack. 5 minutes with a decent level scan tool can tell you the if the problem is mechanical, ignition, or fuel related.
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How to increase your vehicle repair invoice . Tell the shop/mechanic what to do and how to do it . Ask to watch all that and you will add 50.00 to the charge.
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Replacing a motor is almost as expensive as getting another car.
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Looks Honda did some tinkering with VCM, 6 to 4 to 3.
Update: I tried a few cylinder disconnections to get a smoother idle and run. Disabling # 3 resulted in added vibrations throughout rpm 600-2400 rpm range. Cyl 5 smoothed the idle nicely, but add back vibes at 1200-2200rpm. Going with the V7 for now.
Yep! I own one of these V6’s. It is the 4.3L in my 2000 S10. This is a great running engine and seems smooth enough but this one has the balance shaft of course. I guess all the parts are the same and the tooling similar enough that this works and cuts costs.
My understanding is that the timing is quite different on these vs. the parent V8.
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I wouldn’t spend a penny on that Hemi.
Tester
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If you disable cylinders it will send air through that bank which will mess up the oxygen sensor readnigs. The rest of the cylinders on that bank will run rich to try to compensate. If you are unable to stop air flow through the disabled cylinder, then remove the oxygen sensor on that bank.
There shouldn’t be any catalytic converter issue if air isn’t flowing through the disabled cylinder.
Is your failed cylinder pumping air through? If it’s a failed lifter, then the valve isn’t opening so air wouldn’t be flowing through.
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Update:
I have put about 5k miles on the v7, only drive it short distances (1-2 hrs max) and go easy on the throttle. Down shift manually when the thumping gets heavy. Runs cherry! And quite the conversation piece … my office mates have a pool going on when and where I break down… suckers!?
Unfortunate it fails Atlanta emissions due to the misfire code. Is it really polluting with the coil and fuel injector disabled? Emissions seems like a bit of a racket. 
The state says new engine (approx $10k) if I want to keep it on the road … Or move to another county that does not test. Rats!
175k miles, in good shape overall… what do you do?
$10k for an engine or trade her (I might get $4k) for a $35k younger and better looking model?
!75,000 miles?
Stick a fork in it.
Tester
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It’s well beyond its expiration date.
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A good rig is worth $14k. A motor is $10k. Doing the math.
If the current engine config is no spark or fuel for the problematic cylinder, probably not a big polluter, but may be polluting a little b/c everything out of the faulty cylinder to the exhaust is pure air, so a lot of O2. The drivetrain computer will compensate by injecting more gasoline to the 7 cylinders that are working, gasoline which isn’t needed. The main emissions effect is probably some increase in hydrocarbons out the tailpipe. Your Cherokee may be exceeding the state’s HC emissions spec in other words. In any event, it won’t pass b/c of the active misfire code. (The extra air and fuel hitting the cat won’t be doing it any good btw).
hmmm … what to do? … if you can get $4k for a 175K mile vehicle with a misfire, that seems like your best bet. Are you certain the new owner would be able to register it given the misfire problem?
Suggest to do a little more research on your options. You may be able to get the emissions test requirement waived after you spend a relatively small amount of money on a fix attempt, even if it doesn’t work. The waiver might only be good one time though. But it would buy you some time.
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While I definitely prefer cleaner air, some improvements definitely seem in order.
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This vehicle is only 10 years old. Assuming that the body and interior are in decent condition, why not fix it, or sell it to someone else who can fix it, or lives outside the emissions testing zone? A 2013 Jeep Grand Cherokee is still a desirable vehicle.
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I think it was junk when it was new, and hasnt gotten better with age.
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If the cylinder is disabled by the computer due to excessive misfires, I wonder if it takes that in to account?
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The MDS system is designed to compensate for 4/8 cylinder operation. Is it smart enough to know only 7 are in use? As a former programmer, it seems like some simple calculations to include in the fuel injection algorithm … assuming the car companies really care about emissions. 
I am not the expert here, does anyone know the specifics of the Jeep programming?