Jeep Grand Cherokee Misfire? How to Diagnose & Fix a Head Gasket

How to Fix Misfire

Experiencing a misfire in your 2020 Jeep Grand Cherokee can be frustrating and concerning. Misfires can lead to rough idling, reduced power, and even potential damage to your engine if left unaddressed. One owner recounted the challenges of working on their vehicle: "5 hours in I finally see the oil filter housing lol Started at 11am 2 trips to harbor freight for tools, fighting the harness clips, dropping my only 10mm socket behind the engine with no magnet to fish it out." — 100naziscalpz [source: https://reddit.com/r/GrandCherokee/comments/1p7plkx/5_hours_in_i_finally_see_the_oil_filter_housing/]. This guide will walk you through diagnosing and addressing a misfire, focusing on the most likely cause based on owner reports.

Symptoms

Owners have reported several symptoms related to potential issues, which can sometimes be misconstrued as misfires. A primary concern is overheating. If your vehicle is running hot, it's crucial to address this immediately as it can be related to a head gasket issue, which, as we'll discuss, is a potential cause of misfires.

Ticking noises can also be an indicator of underlying problems. While not directly a misfire symptom, unusual engine noises should always be investigated to rule out any mechanical issues that might contribute to misfires. Listen closely to pinpoint the source of the noise.

Another related symptom reported is general overheating. This can be particularly noticeable, especially during hotter days or under heavy load. A malfunctioning cooling system could contribute to engine problems that might manifest as misfires. Keep an eye on your temperature gauge.

Finally, observe any unusual behavior, particularly at night. While seemingly unrelated, conditions like a "20 degree night" can highlight pre-existing issues, as temperature fluctuations can affect the performance of various components.

Most Likely Cause

Based on owner reports, the most likely cause of a misfire in your 2020 Jeep Grand Cherokee is a failing head gasket. The head gasket seals the engine's cylinders, preventing coolant and oil from mixing and ensuring proper compression. When the head gasket fails, it can lead to coolant leaking into the cylinders, causing a misfire. This occurs because the presence of coolant interferes with the combustion process.

A blown head gasket can also cause a loss of compression in one or more cylinders. This loss of compression dramatically reduces the cylinder's ability to ignite the air/fuel mixture properly, leading to a noticeable misfire. This is why a compression test is a key part of the diagnostic process.

Overheating is often a primary indicator of a potential head gasket issue. When the head gasket fails, it can disrupt the cooling system's ability to regulate engine temperature effectively. Over time, repeated overheating can cause significant damage to the engine's internal components, further exacerbating the misfire issue.

How to Diagnose

Diagnosing a misfire related to a head gasket requires a systematic approach:

1. Check for Diagnostic Trouble Codes (DTCs): Use an OBD-II scanner to check for any stored trouble codes. A misfire will often trigger codes like P0300 (Random/Multiple Cylinder Misfire), P0301 (Cylinder 1 Misfire), P0302 (Cylinder 2 Misfire), etc. This provides a starting point.

2. Visual Inspection: Carefully inspect the engine for any obvious signs of coolant leaks around the head gasket. Look for milky residue on the oil dipstick, which indicates coolant mixing with the oil.

3. Compression Test: Perform a compression test on each cylinder. A cylinder with significantly lower compression than the others is a strong indicator of a head gasket leak or other internal engine damage.

   • Tool Required: Compression tester kit.

4. Coolant System Pressure Test: Use a coolant system pressure tester to check for leaks in the cooling system. If the pressure drops rapidly, it suggests a leak, potentially at the head gasket.

   • Tool Required: Coolant system pressure tester.

5. Block Test: A block test involves using a chemical tester to detect the presence of combustion gases in the coolant. If the test fluid changes color, it indicates that exhaust gases are leaking into the coolant, which is a sign of a head gasket failure.

   • Tool Required: Block test kit.

Step-by-Step Fix

Replacing a head gasket is a complex repair that requires mechanical skill and the right tools. If you're not experienced, it's best to consult a professional. However, here are the general steps:

1. Preparation: Disconnect the battery. Drain the coolant and engine oil.
2. Remove Intake and Exhaust Manifolds: Disconnect and remove the intake and exhaust manifolds from the cylinder head.
3. Disconnect Wiring and Hoses: Carefully disconnect all wiring harnesses, hoses, and vacuum lines connected to the cylinder head.
4. Remove Valve Cover: Remove the valve cover to expose the valvetrain components.
5. Remove Rocker Arms and Pushrods (if applicable): Depending on the engine configuration, you may need to remove the rocker arms and pushrods.
6. Remove Cylinder Head Bolts: Loosen and remove the cylinder head bolts in the reverse order of the tightening sequence. This helps prevent warping.
7. Remove Cylinder Head: Carefully lift the cylinder head off the engine block. It may be stuck, so use gentle persuasion.
8. Clean Mating Surfaces: Thoroughly clean the mating surfaces of both the cylinder head and the engine block. Remove any old gasket material.
9. Inspect Cylinder Head: Inspect the cylinder head for any cracks or damage. Have it resurfaced if necessary.
10. Install New Head Gasket: Place the new head gasket onto the engine block, ensuring it is properly aligned.
11. Reinstall Cylinder Head: Carefully lower the cylinder head onto the block, aligning it with the head gasket.
12. Install Cylinder Head Bolts: Install new cylinder head bolts (torque-to-yield bolts are often recommended). Tighten the bolts in the specified sequence and to the specified torque specifications using a torque wrench.
13. Reassemble Components: Reinstall all the components you removed, including the rocker arms, pushrods, valve cover, intake and exhaust manifolds, wiring harnesses, and hoses.
14. Refill Fluids: Refill the engine with fresh coolant and oil.
15. Start Engine and Check for Leaks: Start the engine and check for any leaks. Monitor the engine temperature and coolant level.

Remember that proper torque specifications and bolt tightening sequences are critical for a successful head gasket replacement. Consult a repair manual specific to your 2020 Jeep Grand Cherokee for these details.

Parts and Tools Needed

• Head gasket set (specific to your engine)
• Cylinder head bolts (new bolts are often recommended, especially if they are torque-to-yield)
• Coolant
• Engine oil
• Oil filter
• Intake and exhaust manifold gaskets
• Valve cover gasket
• OBD-II scanner
• Compression tester kit
• Coolant system pressure tester
• Block test kit
• Torque wrench
• Socket set
• Wrench set
• Screwdrivers
• Pliers
• Scrapers
• Cleaning solvents

While specific part numbers will vary based on your engine configuration (3.6L V6, 5.7L V8, etc.), be sure to consult your local parts store or a reliable online retailer.

Real Owner Costs

The cost of repairing a head gasket can vary significantly depending on whether you choose to do it yourself or hire a professional mechanic.

DIY:

• Head gasket set: $100 - $300
• Cylinder head bolts: $50 - $150
• Coolant and oil: $50 - $100
• Tools (if needed): $100 - $300
• Total DIY Cost: $300 - $850

Keep in mind that DIY repair requires a significant time investment and carries the risk of complications if not done correctly. As one owner shared, describing a simpler repair: "5 hours in I finally see the oil filter housing lol Started at 11am 2 trips to harbor freight for tools, fighting the harness clips, dropping my only 10mm socket behind the engine with no magnet to fish it out." — 100naziscalpz [source: https://reddit.com/r/GrandCherokee/comments/1p7plkx/5_hours_in_i_finally_see_the_oil_filter_housing/]. This gives some insight into the potential struggles faced during automotive repair.

Professional Mechanic:

• Labor: $800 - $2000+ (depending on the shop rate and complexity of the job)
• Parts: $200 - $500 (including head gasket set, bolts, fluids, etc.)
• Machine shop services (if cylinder head resurfacing is needed): $100 - $300
• Total Professional Cost: $1100 - $2800+

While more expensive, hiring a professional ensures the job is done correctly and often comes with a warranty.

Prevention

Preventing head gasket failure involves maintaining your 2020 Jeep Grand Cherokee's cooling system and engine properly.

1. Regular Coolant Flushes: Follow the manufacturer's recommended maintenance schedule for coolant flushes. Old coolant can become acidic and corrode the cooling system components, including the head gasket.
2. Monitor Engine Temperature: Pay attention to your engine temperature gauge. If you notice the engine overheating, address the issue immediately. Don't continue driving with an overheating engine.
3. Check for Leaks: Regularly inspect the engine for any signs of coolant or oil leaks. Address any leaks promptly to prevent them from worsening and potentially damaging the head gasket.
4. Avoid Overloading: Avoid putting excessive strain on the engine, such as towing heavy loads beyond the vehicle's capacity or driving aggressively for extended periods.
5. Use Quality Fluids: Use high-quality coolant and engine oil that meet the manufacturer's specifications.

Taking proactive steps to maintain your engine will greatly reduce the risk of head gasket failure and keep your vehicle running smoothly.

What Owners Say

Real experiences from JEEP owners:

Owner Experiences

"Opted to get the Falken wild peak A/T tires…. Don’t think I’ll ever buy a different tire." — Ok_Zookeepergame8827 (source)

"I love it, but it’s definitely not for everyone, especially since the Limited X trim is meant to be more sporty vs rugged. It rides great, getting 18mpg average and no road noise." — Professional_Weird28 (source)

"5 hours in I finally see the oil filter housing lol Started at 11am 2 trips to harbor freight for tools, fighting the harness clips, dropping my only 10mm socket behind the engine with no magnet to fish it out." — 100naziscalpz (source)

FAQ

Q: How long does it take to fix a misfire caused by a head gasket?

A: Replacing a head gasket is a labor-intensive job. A professional mechanic will typically spend 8-12 hours on the repair. If you're doing it yourself, expect to spend significantly longer, potentially over a weekend.

Q: Can I drive with a misfire?

A: It's not recommended. Driving with a misfire can damage your engine and catalytic converter. It's best to diagnose and repair the issue as soon as possible.

Q: Is a head gasket issue a common problem on the 2020 Jeep Grand Cherokee?

A: While not necessarily rampant, head gasket failures can occur on the 2020 Jeep Grand Cherokee, especially if the cooling system isn't properly maintained or if the engine is subjected to frequent overheating.

Q: DIY vs mechanic - what's recommended for a head gasket replacement?

A: Replacing a head gasket is a complex repair best left to a professional mechanic unless you have significant experience working on engines. The precision required for torqueing bolts and ensuring proper sealing makes it a challenging DIY project. As one owner put it, even a seemingly simple task can become complicated: "Started at 11am 2 trips to harbor freight for tools, fighting the harness clips, dropping my only 10mm socket behind the engine with no magnet to fish it out." — 100naziscalpz [source: https://reddit.com/r/GrandCherokee/comments/1p7plkx/5_hours_in_i_finally_see_the_oil_filter_housing/].

Q: What are the symptoms of a blown head gasket?

A: Common symptoms include overheating, white smoke from the exhaust, coolant loss, milky oil, and misfires.

Q: How can I prevent future misfires?

A: Ensure you follow the recommended maintenance schedule, especially for coolant flushes and spark plug replacements. Monitor your engine temperature and address any issues promptly. As one owner stated regarding their tire choice: "Opted to get the Falken wild peak A/T tires…. Don’t think I’ll ever buy a different tire." — Ok_Zookeepergame8827 [source: https://reddit.com/r/GrandCherokee/comments/1n8lvbv/new_tires/]. Taking the time to select the right parts and maintain them properly can keep this 2020 Jeep Grand Cherokee running smoothly.