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Will not run on anything less then 87 octane

96killgore

NAXJA Forum User
Location
San Antonio, TX
I have a 96 xj with 4.0 engine and only aftermarket work is a cold air intake. Long story short ive owned my xj for a little over a year ive done full tune up, gas clean, injector clean, everything you can think of but i still have the same problem of not being able to run on normal grade gas. It runs fine on high octane 93 and normally runs ok on 87 but occasionally act up, but if i run it on regular 85 it will stall and not start until i put octane boost in it and then it will start almost right up. Anyone have the same problem or any ideas on what to do? :NAXJA:
 
What brand and part number of spark plugs ? Describe the color/appearnace of the spark when you test it, weak and kinda orange, or bright blue and snapping ? Test the coil. Load test the battery.
 
I find the best bet to be champion copper plugs. Run the smoothest. I've seen 4.0 engines have all kinds of harshness and rough running problems with some of the crazy plugs you can get these days

Sent from my SM-G950U using Tapatalk
 
The engine is NOT designed to run on15% alcohol /ethanol .The ECM cannot compensate for the alcohol mixture.Even the 10% mix is a struggle for some.
A flex-fuel vehicle is not to run the mix for a long time and should have regular gas run thru it from time to time
 
The min Octane is 87. 85 octane is somewhat common in the Rockies due to the elevation. If you're using E85, STOP! As Wayne says above.
 
They've been trying to ban 85 octane(barely regular) for some years now and the 4.0 was designed for 87 min!
 
Yes stop trying to use E85 in a vechile its not intended to run on.corn
 
The min Octane is 87. 85 octane is somewhat common in the Rockies due to the elevation.

^Bingo.^ My '96 4.0 ran fine on 85-octane where I could buy it (Colorado) because of the elevation. Where I live is like 4,500 ASL and I took the thing a few places that were pushing 10,000 ASL. A 4.0 is designed to run on 87-octane at sea level, which, if you're in San Antonio, you're basically at.
 
My spark plugs, wires, cap and rotor are all new and i have Bosch double platinum. But yes i live in San Antonio, and gass is 85 reg, 87 plus, and 93 premium. But if your saying that these 4.0 are ment to run in 87 at sea level it makes since.
 
I would also ditch the Bosch's and get some Champions or NGK's.
 
My spark plugs, wires, cap and rotor are all new and i have Bosch double platinum. But yes i live in San Antonio, and gass is 85 reg, 87 plus, and 93 premium. But if your saying that these 4.0 are ment to run in 87 at sea level it makes since.


Ditto on running the oem champions. With some of the specialty plugs, quite often their cross reference will put in you into a colder plug when can foul easier. It's safer than crossing to a hotter plug though, which can cause knocking and damage from pre-ignition.
 
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