Jeep Jl Misfiring

[Jab16]

Jeep JL 2018 having a cylinder 4 misfire after all spark plugs have been replaced, as well as coils. It starts with the Start/stop light turning on and then the check engine light followed by shaking when idling. I have also had to add coolant often and I am not usre if the two are related. The check engine light and start stop light will be on some days and off on other days. I have taken it into the shop mulitple times and was told that nothing is wrong it is just a Jeep. Anyone had the same issue and have suggestions to help? And/or recomendations for a decent Jeep dealership that can properly diagnose near Humble Tx area.

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[GATORB8]

Oil clean?
Blowing smoke?
How did plug 4 look when pulled?

 

[Bobby Hank]

Find another shop for sure. "It's just a Jeep" is unacceptable. If not under warranty anymore I'd avoid the dealerships. Find a reputable shop, just my opinion. Good luck!

 

[VKSheridan]

Plug in an OBDC reader and check for codes. It could be something as simple as a dirty air or fuel filter, O2 sensor, crank position sensor.

 

[Willys41]

If you are losing coolant and can't find a leak and it is missing you may have a blown head gasket

 

[jeepoch]

@Jab16,

Jillian, yes to all the above. An OBDII reader will certainly give you way more information to go on.

I'm assuming you have the 2.0L Turbo but it really shouldn't matter. The diagnostic trouble codes (DTC's) should be rather telling. Misfires can be caused by a few factors but not a lot. For a misfire on just a single cylinder the potential causes go down rather dramatically. With multiple cylinder misfires, things like input manifold air, upstream and downstream O2 sensors, fuel pump, fuel line or even bad fuel cannot be ruled out.

I'm not certain you've captured explicitly cylinder #4 misfires or you were indicating you have the four banger in general. But with single piston misfires, a lot of the above common things can pretty much be ruled out. So this leaves (not in any order of relevance):

Piston damage:
A bad ring or a scarred cylinder wall, leading to lost compression. Blue smoke here is a telling give-away.

Fuel Injector clogging:
Not enough petrol in the fuel/air mix causing a lean condition preventing proper combustion.

Fuel Injector failure:
Lack of proper pulsewidth control leading to too rich of a fuel/air mixture again preventing proper combustion.

Spark Plugs:
Insufficient, no spark or improper timing would lead to improper detonation.

Blown Head Gasket:
This allows radiator coolant into the combustion chamber thus disturbing the stoichiometric fuel/air mix preventing combustion.

So based on your data, I'd rule out a spark issue. If no blue smoke it's not likely burning oil due to ring or piston damage. So I'd focus on either:
a. Fuel Injector failure
b. Bad Head Gasket seal

Since you need to add coolant, I'd highly suspect item b above. Can't say for sure without more data, or a hands on inspection, but we're able to deduce quite a bit from just your short description.

For your mechanic not to come up with something more specific, I'd certainly fire that poser.

Regardless, the DTC's can be collected, searched for on the Internet and can be used to absolutely determine the root cause. A lack of any Fuel Injector fault will likely prove a blown head gasket seal.

Hope this helps,
Jay

 

[Jeep Wick]

Jeep JL 2018 having a cylinder 4 misfire after all spark plugs have been replaced, as well as coils. It starts with the Start/stop light turning on and then the check engine light followed by shaking when idling. I have also had to add coolant often and I am not usre if the two are related. The check engine light and start stop light will be on some days and off on other days. I have taken it into the shop mulitple times and was told that nothing is wrong it is just a Jeep. Anyone had the same issue and have suggestions to help? And/or recomendations for a decent Jeep dealership that can properly diagnose near Humble Tx area.

I'm going to assume you are one of the first to have carbon buildup. It's the Achille's heel of direct injection. I would suggest finding a shop that does walnut blasting, they will need to pull the intake manifold. You might be able to get a scope/camera in there first to confirm.

 

[Jab16]

If you are losing coolant and can't find a leak and it is missing you may have a blown head gasket

It was in fact a blown head gasket. Took it to an actual Jeep shop and 10k later no more misfiring!

 

[Willys41]

It was in fact a blown head gasket. Took it to an actual Jeep shop and 10k later no more misfiring!

Problems like this is exactly why I installed the RPM Extreme JL fan controller
I have been running it for a year and have not seen over 212 degrees and that was only for a few minutes pulling a 4000 ft. to 8000 ft. clime over a mountain pass. Most of the time it runs 188 to 195.
Also my oil temps are down 25 degrees.

http://www.rpmextreme.com/Product/311/Jeep-JL-PWM-FAN-CONTROLLER.aspx

 

[Birdman]

Had the coolant leak like that on my 2018 and it was a leaking EGR valve.

 

[mwilk012]

Had the coolant leak like that on my 2018 and it was a leaking EGR valve.

EGR cooler, maybe. Not the valve.

 

[Diamond ?]

Jeep JL 2018 having a cylinder 4 misfire after all spark plugs have been replaced, as well as coils. It starts with the Start/stop light turning on and then the check engine light followed by shaking when idling. I have also had to add coolant often and I am not usre if the two are related. The check engine light and start stop light will be on some days and off on other days. I have taken it into the shop mulitple times and was told that nothing is wrong it is just a Jeep. Anyone had the same issue and have suggestions to help? And/or recomendations for a decent Jeep dealership that can properly diagnose near Humble Tx area.

I'm currently having the same issues...had the spark plugs and cylinders replaced still the same....running terrible

 

[mwilk012]

I'm currently having the same issues...had the spark plugs and cylinders replaced still the same....running terrible

Leaking head gasket. How mechanically savvy are you?

 

[Diamond ?]

I'm not and my mechanic won't touch it...it's been in and out of the shop...last shop was on Monday they said my left cylinder head, camshaft and lifters need to be replaced ...not even sure if parts are available....cost $4500...I'm to the point where I'm might just get rid of it...waited over a year for the parts to get the recall with the clutch issue fixed...the corrosion issue ....I'm over it!

 

[Diamond ?]

I contacted Jeepcares...they said to bring it to the dealer...I'm not sure what to do at this point...49k miles

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