The 3 Most Common Honda 1.5T L15B7 Engine Problems

The Honda L15B7 VTC 1.5 turbo engine is a new direction for Honda. The engine uses a single turbo and direct injection to squeeze more power out of the small engine. However, no engine is perfect and this applies to the Honda 1.5T engine. This is especially true when newer tech is used, such as direct injection. In this article, I discuss the most common Honda 1.5T engine problems including fuel dilution of the oil, carbon build-up, and spark plugs.

Honda 1.5 Turbo Engine Problems

• Fuel dilution of oil
• Carbon build-up
• Spark plugs

Throughout this article we discuss the above 1.5T issues in greater depth. However, it’s a good time to add a few notes before diving in. Simply because these problems make the list does not mean every Honda L15B7 will run into these faults.

There are also many other things that can go wrong with the 1.5 turbo and that applies to any engine. Finally, we’re classifying these problems as the “most common” for a reason. It doesn’t necessarily mean they are actually very common issues. That said, let’s jump in and discuss the 3 most common problems on the Honda 1.5 Turbo.

1) Engine Oil Dilution

Fuel diluting the engine oil is an interesting topic on the Honda L15B7 engine. To note – some fuel dilution is natural and it occurs on most engines. However, there are some cases where the engine experiences too much dilution of the oil. It’s mostly a problem for 1.5T engines in cold weather places. The colder the engine the more likely fuel is to stick to the cylinder walls. It’s then picked up by the engine oil. Honda 1.5 Turbo engines are highly efficient and take a while to heat up. As such, engines in cold places that go on shorter drives are more prone to the fuel dilution problems.

This is an issue for several different reasons. Some owners report the dilution causes stalling, misfires, and power loss. However, fuel dilution of engine oil poses risks to long-term reliability of the 1.5 Turbo engine. Too much fuel in the oil affects the oils ability to properly lubricate moving parts. In turn, this may lead to increased stress and wear on Honda 1.5T engine internals.

Honda offered an extended warranty for an additional year and unlimited mileage. It definitely can’t hurt to have that extra coverage. However, internal wear often won’t show itself until years down the road. They also issued software updates to help mitigate the 1.5 Turbo fuel dilution problems.

Fuel Dilution Symptoms

• Stalling
• Misfires
• Power loss

In some cases too much fuel dilution leads to engine stalling, misfires, and power loss. However, it’s possible to have no symptoms of oil dilution on the Honda 1.5T engine. As such, it may be a good idea to perform an occasional oil analysis. It’s simple to do and pretty cheap. This will tell you how much dilution your specific engine is subject to. You can then adjust the oil change interval accordingly. Honda recommends a 9,000 mile OCI, but changing the oil sooner can help prevent too much dilution.

How to Avoid Fuel Dilution of Oil

Fortunately, there are ways to avoid fuel diluting the 1.5T engine oil. Here are a few good ideas:

• Avoid excessive idling
• Allow engine to warm up before using too much power
• Change oil sooner

Most dilution occurs on a cold engine as the fuel is more likely to stick to cold cylinder walls. It also happens while idling for too long as the engine internals will cool down quickly. Drive gently as the engine warms up, which is a good idea on a turbo engine regardless of any fuel dilution. Finally, you may consider changing the Honda 1.5 Turbo engine oil sooner than the 9,000 mile recommendation.

2) Carbon Build-Up Issues

Carbon build-up on the L15B7 is still somewhat unknown. However, some build-up of carbon deposits on the intake valves of direct injected (DI) engines is natural. It’s one of the biggest downsides of DI engines. Since fuel is sprayed directly into the cylinder there is no fuel flowing through the intake ports. Over time, engines naturally produce some oil blow-by. Oil makes its way into the intake tract where it sticks to the back of the intake valves. Port injection allows fuel to spray over the intake valves which cleans them.

However, without fuel hitting the valves on DI engines that oil sticks to valves over time. The degree of build-up depends how well the Honda 1.5 Turbo manages and reduces oil blow-by. Chances are Honda still has a few kinks to work out as direct injection is pretty new to Honda engines. Either way, carbon build-up happens on DI engines. It’s just a matter of whether 1.5T problems start showing themselves at 60,000 miles or 120,000 miles.

Carbon Build-Up Symptoms

A few symptoms of carbon build-up on the intake valves include:

• Misfires
• Rough idle
• Stuttering
• Power loss

As the oil deposits build-up and harden they restrict air-flow into the Honda 1.5T engine. This can cause a ton of drive-ability issues once there are excessive carbon deposits. Misfires and rough idle are two of the most common symptoms of Honda 1.5 Turbo carbon build-up problems. You may also notice a little stuttering or hesitation while accelerating. Power loss is another symptom as the cylinders receive less air. However, carbon deposits form over a long period of time so power loss likely isn’t noticeable.

Honda 1.5T Carbon Build-Up Solutions

Walnut blasting is usually the best method to remove carbon deposits on the intake valves. It’s a fairly labor intensive job, but no expensive parts are required other than some tools. Walnut blasting for the 1.5 Turbo engines will likely come in around $300-600. Cleaning the intake valves also isn’t an urgent repair and some may simply live with the symptoms of carbon build-up for the longer term. However, it’s a good idea to clean the intake valves when the time comes to maintain drivability.

3) Spark Plug Problems

We’ll speed things up moving through this section. Spark plug issues on the Honda 1.5 Turbo are a pretty small problem. It’s standard wear and tear stuff, so it may not even be worth the mention. However, premature spark plug failure is possible on the Honda 1.5T for several reasons. Notably, the engine is so efficient it takes a while for it to warm up. Cold engines aren’t good for many reasons like we touched on with the oil dilution problems.

It also affects spark plug performance. They need heat to properly operate for the long-term. Cold spark plugs can actually get build-up too – as with the 1.5 Turbo intake valves. Once deposits form on the plugs it affects their ability to properly ignite the air-fuel mixture in the cylinder.

Additionally, turbo engines are known to burn through spark plugs a lot faster than naturally aspirated engines. This is especially true for those who are a bit more throttle happy and enjoy using the turbochargers boost. Some of us in the BMW turbo world are used to replacing spark plugs every 10,000 to 30,000 miles. It’s unlikely the Honda 1.5 engine will consume spark plugs that quickly. However, the point remains. Turbo engines aren’t easy on spark plugs.

Honda 1.5 Turbo Spark Plug Symptoms

• Misfires
• Power loss
• Rough idle
• Stuttering / hesitation

These symptoms are pretty similar to what happens with excessive carbon build-up. Once the spark plugs begin failing they cannot generate a big enough spark to ignite the air-fuel mix. This causes the cylinder(s) to misfire, which causes other symptoms like power loss, rough idle, and stuttering. Spark plugs are cheap and easy to replace so don’t overlook these simple parts.

Spark Plug Replacement

Spark plugs for the Honda 1.5 Turbo come in around $8-20 each, depending on where you source the parts. It’s a good idea to replace all 4 at the same time, so the part cost will come in around $30-80. Not bad at all. Even better, almost anyone can replace spark plugs in their driveway in less than an hour. If you go to a repair shop expect to pay an extra $50-100 to replace the 1.5T plugs.

Honda 1.5 Turbo Reliability

Is the Honda 1.5T engine reliable? Yes, it’s a pretty reliable engine all-around. We’ll give the Honda 1.5 Turbo above average remarks for reliability. It’s still a newer engine so time will tell how they hold up in the longer-term. The 1.5T engine suffers from a few common problems, but nothing too major in the grand scheme. Though, it’s important to beware of oil dilution as too much can affect the 1.5 Turbo longevity. Otherwise, the Honda 1.5T is a solid, reliable engine.

That said, for those not used to turbo engines the maintenance can be a bit more demanding. Turbos are a bit harder on wear and tear parts like spark plugs and ignition coils. It also adds a lot of extra hardware to the engine that can have problems or fail.

Nonetheless, with proper maintenance the Honda 1.5 Turbo shouldn’t have any issues making it past 200,000 miles. If you’re experiencing fuel dilution it’s a good idea to shorten the oil change interval. Keep up with maintenance and stay on top of problems when they pop up. Do this and chances are you’ll have a great, reliable experience with the 1.5T.

Honda L15B7 Common Problems Summary

All things considered, the Honda 1.5 Turbo is a great engine. It’s small and efficient all while providing plenty of power and torque for most drivers and situations. Though, the engine uses some technology a bit newer to Honda engines. Turbos and direct injection add some additional parts and potential complications. Notably, direct injection causes carbon build-up that will need cleaning at some point.

The Honda 1.5T is also so efficient that it takes a while for the engine to reach operating temperatures. This can cause issues with excessive fuel diluting the engine oil. Fortunately, they offered some software updates and an extended warranty. However, fuel dilution on the 1.5 Turbo can have serious long-term reliability and longevity concerns.

Otherwise, the Honda 1.5 Turbo doesn’t suffer many common problems. Spark plugs are a pretty minor aspect in the grand scheme. However, they highlight the fact turbo engines can be a bit more demanding on upkeep. Maintain the 1.5T well and it will likely reward you with a reliable and long life.

Looking for more on the 1.5T engine? Check out our additional guides including the best Honda 1.5T performance upgrades and best Honda engines of all time.