Maintaining a used vehicle, especially a robust SUV like the 1999 Toyota 4runner, often starts with a comprehensive tune-up. If you’ve recently acquired a 1999 Toyota 4Runner, or if you’re noticing a dip in fuel economy, understanding the essentials of a proper tune-up is crucial. A well-maintained 1999 4Runner should deliver around 18-20+ MPG (city/highway). If your numbers are falling below this range, numerous factors could be at play, but thankfully, many are easily addressed with routine maintenance and targeted fixes.
To begin, it’s highly recommended to consult resources that detail common maintenance tasks for your 1999 Toyota 4Runner. These resources provide step-by-step guides and community insights that can be invaluable for both novice and experienced DIYers.
Diagnosing Engine Issues: Check Engine Codes
The first step in optimizing your 1999 Toyota 4Runner’s performance and fuel efficiency is to rule out any significant mechanical issues. Start by checking for any active “Check Engine” codes. Fault codes related to the intake, engine, exhaust, or drivetrain systems can significantly impact fuel mileage and overall performance.
You can easily retrieve these codes using an OBD-II scanner. Many auto parts stores offer free code reading services, making it a readily accessible diagnostic step. To understand the meaning of any codes you retrieve, refer to a comprehensive Toyota OBD-II Trouble Code database. This will help you pinpoint potential проблемs and guide your tune-up process.
Resetting the EFI Relay: Relearning Driving Habits
A lesser-known but effective technique, especially when you purchase a used 1999 Toyota 4Runner, is resetting the Electronic Fuel Injection (EFI) relay. This is a practice often employed by used car dealerships to help vehicles adapt to new drivers. The EFI system in your 1999 Toyota 4Runner learns and adapts to the driving style of the previous owner. Resetting the EFI map allows the vehicle to “forget” these old driving habits and learn your driving style instead.
This relearning process involves your 4Runner adapting to your acceleration patterns, cruising speeds, and overall driving behavior, optimizing fuel injection accordingly. While resetting the EFI relay doesn’t guarantee an immediate MPG increase, it often results in a more responsive and “peppy” feel. Even without resetting, the EFI system will eventually adjust to your driving style, but manually resetting it accelerates this adaptation.
It’s also beneficial to reset the EFI relay whenever you make significant changes to your 1999 Toyota 4Runner’s drivetrain, such as replacing the air filter, cleaning intake components, installing a cold air intake, or changing tire sizes or exhaust systems.
To reset the EFI relay on your 1999 Toyota 4Runner, locate the largest EFI relay in the fuse box, typically found on the driver’s side of the engine bay. With the battery connected, remove this relay for about 30 minutes and then reinstall it. This simple procedure can help your 1999 4Runner optimize its fuel efficiency and responsiveness based on your driving style.
Air Filter Replacement: Enhancing Engine Breathing
One of the simplest and most immediate ways to improve the fuel efficiency of your 1999 Toyota 4Runner is to replace the air filter. A clogged or dirty air filter restricts airflow to the engine, forcing it to work harder and consume more fuel. Regular air filter replacement is a fundamental aspect of 1999 Toyota 4Runner maintenance.
When selecting a new air filter for your 1999 Toyota 4Runner, consider the different types available, primarily oiled vs. dry filters. Both have their advantages, and the best choice often depends on your driving environment and preferences. Reputable brands known for quality air filters compatible with the 1999 Toyota 4Runner include OEM (Toyota), TRD, aFe, Amsoil, and K&N. Choosing a high-quality air filter ensures optimal engine performance and fuel economy for your 1999 4Runner.
Toyota 4Runner Air Filter Replacement
Cleaning the MAF Sensor and Throttle Body: Restoring Airflow Efficiency
Another straightforward yet impactful maintenance task for your 1999 Toyota 4Runner is cleaning the Mass Air Flow (MAF) sensor and throttle body. These components are prone to accumulating dirt and carbon deposits over time, which can impede their function and reduce fuel efficiency. It’s recommended to clean the MAF sensor and throttle body of your 1999 Toyota 4Runner approximately every oil change to maintain optimal performance.
A dirty MAF sensor can provide inaccurate readings to the engine control unit (ECU), leading to an improper air-fuel mixture. Similarly, a carbon-clogged throttle body can restrict airflow into the engine. Combined, these issues can reduce your 1999 Toyota 4Runner’s MPG by as much as 25%. Detailed guides are available online, offering step-by-step instructions on how to safely and effectively clean these components, helping you restore lost fuel economy and engine responsiveness in your 1999 4Runner.
SeaFoam Treatment: Deep Engine Cleaning
For a more intensive internal engine cleaning, consider using SeaFoam in your 1999 Toyota 4Runner. SeaFoam is a petroleum-based product designed to clean fuel injectors, valves, and other internal engine parts. It helps remove carbon buildup and deposits that accumulate over time, improving engine performance and potentially fuel economy in your 1999 Toyota 4Runner.
The SeaFoam treatment process typically involves adding SeaFoam to the engine crankcase a few hundred miles before an oil change, as well as adding it to the fuel tank. For a more thorough cleaning, SeaFoam can also be sprayed directly into the intake plenum. This comprehensive treatment helps to clear out carbon deposits from various parts of the engine.
It’s worth noting that while SeaFoam is effective, it can sometimes dislodge enough carbon and gunk to potentially foul oxygen (O2) sensors or spark plugs. Therefore, be prepared to inspect and possibly replace these components after a SeaFoam treatment on your 1999 Toyota 4Runner. It’s generally advisable to perform a SeaFoam treatment as one of the initial steps in a comprehensive tune-up. The process is often accompanied by noticeable white smoke from the exhaust as the carbon deposits are burned away, which can be quite visually striking.
PCV Valve Replacement: Maintaining Engine Pressure Balance
The Positive Crankcase Ventilation (PCV) valve plays a crucial role in your 1999 Toyota 4Runner’s engine efficiency. The PCV valve vents excess pressure from inside the crankcase, reducing internal engine resistance and promoting smoother operation. PCV valves are known to degrade over time and typically need replacement every 5 years or so.
A malfunctioning PCV valve can lead to a decrease in fuel efficiency, potentially reducing your 1999 Toyota 4Runner’s MPG by 2-3 miles. Fortunately, replacing the PCV valve is a quick and inexpensive maintenance task. It usually takes about 5 minutes to replace. The PCV valve is typically located on top of the engine. Simply pull out the old valve and grommet using pliers, and install the new valve and grommet in reverse order. For optimal results, it’s recommended to reset your 1999 Toyota 4Runner’s EFI system after replacing the PCV valve. You can obtain the necessary parts, PCV valve (part number 12204-62010) and PCV grommet (part number 90480-18001), from a Toyota dealership for under $15 in total.
O2 Sensor Inspection and Replacement: Ensuring Correct Fuel Mixture
Oxygen (O2) sensors are critical components in your 1999 Toyota 4Runner’s engine management system. They monitor the oxygen levels in the exhaust gases and provide feedback to the ECU, which then adjusts the air-fuel mixture for optimal combustion. Faulty or degraded O2 sensors are a common cause of significantly reduced fuel economy in the 1999 Toyota 4Runner.
If you are experiencing noticeably poor MPG in your 1999 Toyota 4Runner, checking and potentially replacing your O2 sensors should be a priority. You can find the correct O2 sensor part numbers for your 1999 Toyota 4Runner online resources dedicated to Toyota parts or through parts websites. Online marketplaces like Amazon often offer competitive prices on O2 sensors. Replacing worn O2 sensors can often restore your 1999 Toyota 4Runner’s fuel efficiency and engine performance.
Spark Plug and Wire Replacement: Optimizing Ignition
Maintaining the ignition system of your 1999 Toyota 4Runner is essential for smooth engine operation and fuel efficiency. This includes regular inspection and replacement of spark plugs and spark plug wires. For the 3.4L V6 engine in the 1999 Toyota 4Runner, it’s crucial to use the correct type of spark plugs. Dual ground plugs are specifically required for this engine.
Recommended spark plugs for the 1999 Toyota 4Runner 3.4L V6 include NGK BKR5EKB-11, OEM Toyota #90919-01192 (made by Denso), and Denso #K16TR11. Using plugs other than these can lead to suboptimal performance. For spark plug wires, reliable options include Bosch 09444 and NGK 4412. Both sets are functionally identical, with the NGK wires featuring a blue outer casing for a slightly different aesthetic. Online tutorials and guides are readily available to assist you with the spark plug replacement process on your 1999 Toyota 4Runner.
Oil Change: Lubrication and Engine Health
Regular oil changes are the cornerstone of any vehicle maintenance schedule, and the 1999 Toyota 4Runner is no exception. Changing the engine oil and filter at recommended intervals ensures proper lubrication, reduces engine wear, and helps maintain optimal engine temperature. For the 1999 Toyota 4Runner, 5W-30 motor oil is the recommended viscosity.
When it comes to oil filters, OEM Toyota filters are widely considered to be among the best in terms of quality and performance. The OEM Toyota oil filter part number is 90915-YZZD1. Using a high-quality oil filter, such as the OEM Toyota filter, helps ensure that your 1999 Toyota 4Runner’s engine is properly protected and performs efficiently. Numerous online guides can walk you through the process of changing the oil in your 1999 Toyota 4Runner.
Fuel Filter Replacement: Ensuring Clean Fuel Delivery
While Toyota may claim that the fuel filter in the 1999 Toyota 4Runner is a “lifetime part,” in reality, it benefits from periodic replacement. Over time, the fuel filter can become clogged with contaminants, especially after 100,000 miles or more. A clogged fuel filter forces the fuel pump to work harder, potentially reducing fuel efficiency and even causing fuel delivery issues in your 1999 Toyota 4Runner.
Replacing the fuel filter is a preventative maintenance measure that can help maintain your 1999 Toyota 4Runner’s performance and fuel economy. The fuel filter part number for the 1999 Toyota 4Runner is 23300-62030. Online resources and forums dedicated to Toyota 4Runners often provide detailed write-ups and guides with pictures to assist you in replacing the fuel filter yourself.
Monitoring Driving Habits: Improving Fuel Efficiency
Beyond mechanical tune-ups, your driving habits significantly impact the fuel economy of your 1999 Toyota 4Runner. Using a device that provides real-time and average fuel mileage readings can be a valuable tool for improving your driving efficiency. Devices like Scangauge II, UltraGauge, and Aeroforce Interceptor can display instantaneous and average MPG, along with other engine parameters.
Instantaneous MPG readings show your current fuel economy at any given moment, while average MPG reflects your overall fuel efficiency over a trip or tank of fuel. By monitoring these readings, you can learn to optimize your driving habits. For example, you’ll notice that aggressive acceleration drastically reduces MPG, while coasting maximizes it. Learning to coast more and accelerate more gently can significantly improve your average fuel economy in your 1999 Toyota 4Runner.
These monitoring devices also typically offer additional features, such as displaying engine temperatures, reading and clearing engine codes, and more. It’s important to note that transmission temperature monitoring is generally only supported on 1999-2002 4Runner models, and may not be available on 1996-1998 models, regardless of the device chosen.
Driveshaft Lubrication: Maintaining Smooth Drivetrain Operation
Ensuring smooth operation of your 1999 Toyota 4Runner’s drivetrain includes regular lubrication of the driveshaft. Driveshaft lubrication is a simple maintenance task that should be performed every few oil changes. Lubricating the driveshaft’s U-joints and slip yokes reduces friction, prevents premature wear, and ensures smooth power transfer.
Online guides and tutorials specifically for 1999 Toyota 4Runners detail the process of lubricating the driveshaft, typically involving the use of a grease gun to apply grease to the zerk fittings on the driveshaft. Regular driveshaft lubrication contributes to the overall longevity and reliability of your 1999 Toyota 4Runner.
Debunking Myths: Throttle Body Spacers and Performance Chips
It’s important to address some common misconceptions regarding performance modifications for the 1999 Toyota 4Runner, specifically throttle body spacers and performance chips.
Throttle Body Spacers: Despite claims of increased power, throttle body spacers generally do not provide any performance benefits for fuel-injected engines like those in the 1999 Toyota 4Runner. Throttle body spacers were more relevant in older carbureted engines, where they could alter carburetor function. However, on modern fuel-injected engines, they are largely ineffective. Dyno tests and real-world experiences have consistently shown that throttle body spacers offer no tangible power gains on vehicles like the 1999 Toyota 4Runner. Therefore, investing in a throttle body spacer for performance enhancement is not recommended.
Performance Chips: Similarly, performance tuning chips marketed for stock, naturally aspirated engines like the 3.4L V6 in the 1999 Toyota 4Runner are generally ineffective. These chips are often marketed with promises of increased power and fuel economy. However, the stock ECU in the 1999 Toyota 4Runner is already optimized for both power and fuel efficiency under normal driving conditions. Performance chips are more relevant in forced induction applications or heavily modified engines where significant adjustments to fuel and timing are needed. For a stock 1999 Toyota 4Runner, performance chips typically offer no real-world benefits and are not a worthwhile investment.
Basic Starter Modifications for 1999 Toyota 4Runner
Beyond tune-up and maintenance, there are some basic and popular modifications that 1999 Toyota 4Runner owners often consider to personalize and enhance their vehicles.
LED Interior Conversion: Many owners of 1999 Toyota 4Runners opt to replace the factory green interior lighting with LEDs. LED interior conversions offer brighter, more modern-looking lighting and are available in various colors. This conversion typically involves replacing bulbs in the instrument cluster, center console, key ring, map lights, and dome lights. LED conversion kits are readily available and can significantly update the interior ambiance of your 1999 Toyota 4Runner.
Toyota 4Runner Interior LED Conversion
Deck Plate Mod: The Deck Plate Mod is a popular DIY modification for 1999 Toyota 4Runners aimed at slightly improving intake airflow and sound. This mod involves cutting a 4-inch hole in the air box (before the air filter) and installing a marine deck plate. With the deck plate cap on, the air box functions as stock. With the cap off, it allows for a less restricted air intake. While performance gains are minimal, many users report improved throttle response and a slightly louder intake sound. Some owners also notice a minor improvement in fuel economy after performing the Deck Plate Mod on their 1999 Toyota 4Runner. This modification is relatively inexpensive and takes about 30 minutes to complete.
Intake Silencer Removal (ISR): The Intake Silencer Removal (ISR) mod is another intake modification often performed on 1999 Toyota 4Runners. The intake silencer is a resonator chamber located in the intake system designed to reduce intake noise. Removing the silencer and replacing it with a straight pipe reduces airflow restriction, potentially improving throttle response and intake efficiency. The ISR mod also noticeably increases intake noise, which can be a desirable or undesirable outcome depending on personal preference. When combined with the Deck Plate Mod, the ISR mod can create an intake setup that approximates the benefits of a cold air intake system, while retaining the option to reseal the intake using the deck plate cap for off-road conditions or water crossings. The ISR mod is also a quick and inexpensive modification, typically costing under $20 and taking less than 30 minutes to complete.
Toyota 4Runner Intake Modifications (Deck Plate & ISR)
Rear Differential Breather Mod: The Rear Differential Breather Mod is a practical modification, especially for 1999 Toyota 4Runners that are used for off-roading or in wet environments. The stock rear differential breather plug can allow water to enter the differential if submerged, potentially causing damage. This mod involves extending the breather plug to a higher location on the vehicle, preventing water ingress. The front differential and transfer case on the 1999 Toyota 4Runner already have extended breathers from the factory, but the rear axle does not. The Rear Differential Breather Mod is a relatively simple and inexpensive modification that adds an extra layer of protection for your 1999 Toyota 4Runner’s rear differential. It typically takes less than 30 minutes and costs under $20 to perform.
Plasti-Dip Emblems/Trim/Wheels: Plasti-Dip is a rubberized coating that can be applied as a spray paint and then peeled off if desired. It’s a popular option for cosmetically modifying emblems, trim, and even wheels on the 1999 Toyota 4Runner. For emblems, you can mask off the area around the emblem, spray Plasti-Dip over the entire area, and then peel off the excess Plasti-Dip from the body, leaving the emblem coated. Plasti-Dip provides a matte finish and is a reversible modification, making it a popular choice for customizing the appearance of a 1999 Toyota 4Runner.
Toyota 4Runner Plasti Dipped Emblems
Tire Size Considerations for 1999 Toyota 4Runner
When considering tire replacements for your 1999 Toyota 4Runner, tire size is a crucial factor.
Stock Tire Size: The stock tire size for the 1999 Toyota 4Runner is typically 31 inches, or 265/70-R16.
Larger Tire Options: You can fit slightly larger 32-inch tires on a 1999 Toyota 4Runner with stock suspension. Common 32-inch tire sizes include 265/75-R16 or 265/70-R17. Installing tires larger than 32 inches generally requires trimming and/or a suspension lift to prevent rubbing. While it is technically possible to fit even 35-inch tires with stock suspension, it necessitates extensive trimming and modification of the fenders and firewall.
When changing tire sizes, it’s important to use a tire size calculator to determine the impact on your speedometer accuracy. Larger tires will result in a speedometer reading that is lower than your actual speed.
TRD Supercharger for 1999 Toyota 4Runner: Performance Upgrade
For owners seeking a significant performance boost for their 1999 Toyota 4Runner, the TRD Supercharger is a highly desirable, albeit more involved, modification. The TRD Supercharger was offered as a dealer-installed option for the 1999 Toyota 4Runner and other models equipped with the 3.4L V6 engine. It was not a factory-installed option but rather an aftermarket upgrade installed by Toyota dealerships.
There are two generations of TRD superchargers for the 3.4L V6, both manufactured by Magnuson and designated as M62 superchargers. Both generations provide similar performance gains. The main differences are in their appearance and ease of maintenance. Resources like GadgetOnline.com offer comprehensive information about TRD superchargers, their operation, and the differences between the generations.
TRD Supercharger (1st Generation):
TRD Supercharger (2nd/4th Generation):
TRD Supercharger Performance Specs (Base): With just the supercharger installed (and no additional fuel modifications), the 3.4L V6 engine in the 1999 Toyota 4Runner sees notable performance gains.
Known Issues with TRD Superchargers:
TRD Superchargers for the 1999 Toyota 4Runner, while potent, are known to have certain potential issues, many of which are related to insufficient supporting fuel modifications. Websites like UltimateYota.com provide detailed lists of these issues, including:
- High gear/low RPM pinging
- High RPM lean out conditions
- Increased wear on automatic transmissions
These issues can often be mitigated by installing Underdog Racing Development’s (URD) 7th injector kit. This kit provides additional fuel to compensate for the increased air volume from the supercharger, especially at higher RPMs and boost levels. The URD kit also includes a tuning computer and cooler spark plugs to optimize timing and prevent detonation.
If a full 7th injector kit is not desired, at a minimum, it’s recommended to install two-step cooler spark plugs, such as Denso Iridium IK22, to help manage combustion temperatures with the supercharger.
Additional Supercharger Issues:
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Belt Slippage: TRD superchargers came with two types of tensioners: static and dynamic. The older static tensioner can be prone to belt slippage under hard acceleration. Upgrading to the dynamic tensioner (part number PTR29-60032) is a common solution. The dynamic tensioner is spring-loaded and automatically maintains proper belt tension.
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Supercharger Wear: The bearings in the supercharger nose cone are a wear item with a service life of around 100,000 miles. The 2nd generation supercharger offers an advantage here as its nose cone can be rebuilt while still installed on the vehicle using a TRD Nose cone rebuild kit (PN: PTR29-35042). The 1st generation supercharger typically requires removal and either professional rebuilding by Magnuson or a DIY rebuild if you have the necessary tools.
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Bypass Valve Failure: The bypass valves on 2nd generation TRD superchargers are known to sometimes fail or develop boost leaks due to rivet failures or dried/cracked rubber components. Replacement bypass valves are available from aftermarket suppliers like LCE Performance.
Supercharger Performance Upgrades:
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Smaller Supercharger Pulley: Smaller supercharger pulleys increase boost levels, resulting in more power. URD offers a range of smaller pulleys for TRD superchargers. Upgrading to a smaller pulley generally requires supporting fuel modifications to accommodate the increased airflow. The stock pulley size is 2.37 inches, producing around 7 psi of boost. A 2.2-inch pulley typically increases boost by 1.5-2 psi, and a 2.1-inch pulley can increase boost by 3.5-4 psi. It’s crucial to monitor boost levels and ensure they remain within safe limits for the supercharger (around 15 psi maximum).
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Methanol Injection: Methanol injection is an alternative or supplementary method to increase fuel delivery and performance in supercharged 1999 Toyota 4Runners. Methanol injection systems inject a mixture of methanol and water into the intake stream, which cools the intake charge and increases octane, allowing for more aggressive tuning and power. Methanol injection can be a cost-effective way to enhance performance, but it requires periodic refilling of the methanol reservoir and careful tuning.
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Cooler Thermostat: Upgrading to a cooler thermostat is often recommended for supercharged 1999 Toyota 4Runners to help manage engine temperatures. The stock thermostat is typically 180°F, resulting in engine temperatures around 193-195°F. A 170°F thermostat, such as the Stant 14077, can help maintain cooler engine temperatures under supercharged conditions, typically around 185-190°F. A 160°F TRD thermostat is also available, but it’s generally recommended only for highly tuned applications and requires careful monitoring of engine temperatures.
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Performance Headers: Performance headers replace the stock exhaust manifolds and are designed to improve exhaust flow, potentially increasing power output by 10-15 horsepower in a 1999 Toyota 4Runner. Brands like TRD, Doug Thorley, and OBX offer performance headers for the 3.4L V6 engine.
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High Flow Exhaust: Complementing performance headers with a high-flow muffler and catalytic converter can further enhance exhaust flow and potentially improve performance. However, replacing the stock catalytic converter with a high-flow unit may trigger an O2 sensor code. In such cases, a URD rear O2 simulator kit can be used to prevent this code.
By addressing these tune-up and maintenance items, and considering potential modifications, you can ensure your 1999 Toyota 4Runner runs optimally, providing both reliable performance and respectable fuel economy for years to come.
