Sudden Engine Cylinder Problem

[2016 Willys Wrangler JK]

I own a 2016 JK Willys with almost 130k miles - which I take pretty good care of (even cleaning the engine bay) and don't abuse it. So this just happened Tuesday morning (8/4/2026) on the drive to work: Approximately 5.5 miles to destination, I get one chime with a blinking yellow check engine light. I cut off the radio to listen for anything unusual - nothing - the warning goes off. I quickly notice the chime and light appear only when I step on the accelerator. Since the remainder of the ride to work is relatively flat, I nursed it the rest of the trip - getting lucky to catch all the green lights along the way, I suppose I triggered the warning light perhaps 8 - 10 times more (again triggered by acceleration). I detected a very slight chugging as I neared my destination. As I pulled into the lot and slowed to park, the engine quietly stalled. I restarted - it ran rough and stalled after 2 seconds or so. I had it flat-bedded to a shop near home. They diagnose a P0303 code to identify cylinder 3 and explain they checked the plug (was burnt) and wires. Then settled on a conclusion of cylinder compression suggesting repairs would be rather expensive - approaching the cost of engine replacement. They also explained they don't do that kind of work, and it would have to be outsourced - they would recommend a shop/someone along with a quote. Which is where I am now. Waiting for a price I expect will come in around $7,000 - $8,000. I'm no expert, so as a logical minded person, I suspect the problem might have something to do with fuel injection into cylinder 3 - hence the problem of no compression. I'm leaning toward having it flat-bedded to a nearly dealer for a second opinion/diagnostics test - maybe they'll come up with other options after they test it. I have a hard time believing my engine "suddenly - mysteriously and unexpectedly" has a problem this serious with absolutely no symptoms or indications leading up to it. Anyone else experience something like this? I'm open to possible explanations/suggestions/advice. Thanks in advance.

 

[BLACKJKU]

Did they do a compression check on the cylinders?

Did they put a new plug and wires on?

Or are they just telling you this to make another Shop some extra money that it needs a new engine?

 

[JeepJeezy]

I'd ask the shop to replace the spak spugs than swap that cylinder 3 coil pack with another cylinder, clear the code and see if the code moves. If it doesn't, then check your injector.

 

[Mopar]

Id want to know what were the compression numbers. If they don’t know, they didn’t check.

The Jeep doesn’t have spark plug wires. It uses coil over plugs. The #3 cylinder is easy to access so easy to test.

Burnt spark plug? Did they show it to you? That sounds unlikely.

Injectors can also cause misfire codes but if they die, you’ll also get fuel injector codes. I had that issue on my 2016 with 81k ish miles. Once the injector died, I also got injector codes.

Fuel injection and compression are two different things. They work together but you can have bad compression and good injectors and bad injectors and good compression.

Acceleration causing issues suggests (but doesn’t guarantee) a fuel injector issue. If you do end up having a bad one, I’d replace all of them and I’d use JL injectors. MUCH cheaper and slightly better.

 

[tJKrider]

Did they do a compression check on the cylinders?

Id want to know what were the compression numbers.

I would have them do both compression and leak down tests. I would want to rule out the valve seat issue that was more widespread from earlier model years.

I'd ask the shop to replace the spak spugs than swap that cylinder 3 coil pack with another cylinder

This is a logical first diagnostic step to help determine the "is/is-not" of what is happening.

 

[Mopar]

If the shop is reputable, the customer shouldn’t have to tell them how to diagnose the problem. Maybe the OP has a lack of compression problem but at this point, we don’t know. I doubt he does have a compression problem but it’s always possible. Testing will confirm or deny it as the problem.

 

[Baja-D]

Seems odd...how does a compression issue burn plugs and wires? Perhaps foul the plug and short out the coil? First thing I would do is look at the burned plug and wires myself. If it is a wire, plug or coil issue that is an easy low cost fix.

 

[tJKrider]

Seems odd...how does a compression issue burn plugs and wires? Perhaps foul the plug and short out the coil? First thing I would do is look at the burned plug and wires myself. If it is a wire, plug or coil issue that is an easy low cost fix.

That's why I suggested a leak down test. If it's a piston ring issue that may not show itself in a compression test. That could be the cause of misfires and oil in the cylinder/on the plug. Valve seat recession will also probably not show up in an explicit compression test.

Your statement is spot on, though, I would want to see the parts firsthand.

 

[2016 Willys Wrangler JK]

I apologize for the delay - it's been a couple weeks of collecting quotes: here's the entire UPDATE:

2016 Jeep Wrangler JK ENGINE REPAIR or REPLACEMENT

Codes Found in System:
P0300 Random multiple misfire
P0303 Cylinder 3 misfire

SHOP 1 - DAVE SUTTER AUTO SERVICE - DIAGNOSIS: $250
Replaced Spark Plug in Cylinder 3
Tested Ignition Coil by swapping to a different cylinder
Checked Injector function via Scan Tool - Injector working
Performed Compression Test on Cylinders 1 and 3.
0 Compression on Cylinder 3; 120psi Compression on Cylinder 1
Suspected bad camshaft causing valve issues as cam problems are a well documented failure on Chrysler 3.6L

SHOP 2 - KREBS CHRYSLER-DODGE-JEEP-RAM DEALER - REPAIR ESTIMATE $5,153 + tax
Cylinder Head Replacement + Gaskets
PCV Valve + Plugs + Oil Filter, Coolant

SHOP 3 - BAUERSTOWN AUTOBODY - REPLACEMENT QUOTE $8,300
JASPER Engine + Installation Kit + Parts & Labor (out the door); Shops must get a better engine price than I did (see JASPER) below.
Owner explained his quote would be lower because he doesn't have overhead costs associated with own/lease of modern diagnostic equipment.

SHOP 4 - BESSEMER AVE AUTO REHAB - REPAIR ESTIMATE $2,515
LONG BLOCK Remove & Replace, Automatic Transmission (consists of cylinder block fitted with pistons, rings, connecting rods, crankshaft and all bearings, cylinder heads, camshafts, timing chain or belt, and sprockets or gears. Includes DexCool (ZXEL-1), Synthetic Engine Oil (5w20 or 5w30), Shop supplies); Parts: $154.90 + Labor $2,218 + Tax $142

SHOP 4 - BESSEMER AVE AUTO REHAB - REPAIR ESTIMATE $1,045
CAMSHAFT - Remove & Replace - All Both Heads
Synthetic Engine Oil (5w20 or 5w30), Oil Filter Shop supplies;
Parts $66 + Labor $920 + Tax $59
This shop was recommended by Jasper but there's no quote for engine replacement.

SHOP 5 - COLLIERS AUTO SERVICE - ESTIMATE $TBD
Quote coming soon. I had my JK flatbedded to this shop 8/25. They're going to examine the overall viability of other major systems before I invest in an engine. They're going to check transmission, ball joints, frame, suspension, exhaust, transfer case, etc.
This shop was recommended by Jasper for engine replacement

JASPER ENGINE QUOTE $8,100
Jeep Wrangler 3.6L $6,373 + Core $500 + Skid $250 + Tax $480 + $494 Installation Kit
This complete gas engine will be completely remanufactured. Every JASPER Engine is
completely disassembled, thoroughly cleaned and inspected. Wear parts- pistons rings and
bearings, among others are replaced with new parts. All castings are remanufactured to exact
dimensional tolerances. The engine will be reassembled and live run tested with checks on oil
pressure, compression and vacuum. This engine includes the block, head(s), oil pump and pan,
timing cover and finishing gaskets. JASPER will need your core returned like-for-like and in
accordance with the specific core policy for this unit within 30 days after delivery ($750 CREDIT).
The limited** warranty on this engine is 36 months or 100,000 miles parts and labor.

JASPER INSTALLATION KIT add-on $494 (up to 25% savings over individually priced parts)
Brand Name Parts known for quality; Warranty labor reimbursement
Belts & Radiator Hoses 3yr/100k mi P+L
Fuel Pump (mechanical) 3yr/100k mi P+L
Water Pump 3yr/100k mi P+L
Plug Wires 3yr/100k mi P+L
Thermostat 3yr/36k mi P+L
Radiator Cap 3yr/36k mi P+L
Oil Filter First Service Interval for Parts, 60 days labor
Fuel Filter First Service Interval for Parts, 60 days labor
Air Filter First Service Interval for Parts, 60 days labor
Breather Filter First Service Interval for Parts, 60 days labor
Rotor First Service Interval - 3 yr/36k mi P+L
Distributor Cap First Service Interval - 3 yr/36k mi P+L
Spark Plugs First Service Interval - 3 yr/50k mi P+L
PCV Valve First Service Interval - 1 yr/15k mi P+L

I'm leaning toward Colliers (hoping for a good price) since they’re evaluating whether the rest of the Jeep is worthy to receive one - directly addressing the biggest remaining uncertainty of the plan: whether putting $8K–$10K into the powertrain is sensible. Your thoughts?
THANKS in advance.

 

[Mopar]

I would now want to know the cause of the low compression. How do the cylinders look? If the cylinders look good, then it’s a valve/cam/lifter issue and the vehicle doesn’t need a new engine. An inspection camera down the spark plug hole will show how the dead cylinder looks. If it looks good, then I’d go the head replacement route

 

[tJKrider]

0 Compression on Cylinder 3

Shop 1 is the only one that provided useful information. I would ask the other shops for the data leading to their diagnosis before I made a decision.

For one cylinder to have zero compression there is a major leak path - head gasket, valve seat recession, stuck valve, hole in piston, damaged rings. I don't see it as likely that the camshaft is the root cause. It may have been damaged as a result, but not the source of the problem.

Note - a leak down test will help determine the cause of the zero compression in that cylinder. I know I'm sounding like a broken record, but it's a common non-invasive diagnosis technique.

 

[Mopar]

Shop 1 is the only one that provided useful information. I would ask the other shops for the data leading to their diagnosis before I made a decision.

For one cylinder to have zero compression there is a major leak path - head gasket, valve seat recession, stuck valve, hole in piston, damaged rings. I don't see it as likely that the camshaft is the root cause. It may have been damaged as a result, but not the source of the problem.

Note - a leak down test will help determine the cause of the zero compression in that cylinder. I know I'm sounding like a broken record, but it's a common non-invasive diagnosis technique.

I agree. And, unless something is very broken, normally a cylinder has some compression…. just not enough to run properly. A leak down test is always good. If it truly has zero compression, a camera down the plug hole should reveal the cause of the total lack of compression.

I’m concerned that the place that diagnosed it may not really know what they are doing. They should have told the OP what the cause of the lack of compression is. It’s not hard to figure out with some diagnostic tools

 

[Jeepridge]

It would be very unfortunate if it was truly a simple valve issue, and they misrepresent it or didn’t do the homework needed to be sure of why there is “zero” compression. It could be a meltdown of some kind, but I don’t think I’ve ever seen an engine that cannot build any compression either not have a crack in the cylinder wall, a lack of rings entirely, or a valve issue. I’m no expert, obviously, but I would hope for a complete understanding myself before I moved forward.

 

[FLY-DOG]

With 130K miles I wouldn't do a top end only; instead I'd replace the entire engine. Does Jeep still sell brand new 3.6 engines for the JK model Wrangler? If so, I'd go with a new motor versus rebuilt. If going rebuilt I would look at Fraser over Jasper. https://fraserengineco.com/3-6-liter-chrysler-dodge-jeep-engines/