We have all seen it. That loyal customer who diligently brings their family workhorse in for service, on time, every time. They follow manufacturer-suggested service intervals and never question a needed repair or suggested service. Then one day they drop it on you. Not only do they have their tried-and-true daily driver, but they also have their weekend cruiser. Maybe it’s an early '50s Packard convertible, a '70s GM A-Body, a first Gen Mustang, or even some Malaise-era land yacht.
But it doesn’t matter, because you are “the one.” The only one that they want to work on their “baby.” As a shop owner, service manager, or technician, it’s a nice feeling to provide such an exemplary service that it results in so much trust. So, you agree, but when the day comes to bring it in they add one more small tidbit of information — this vehicle is no longer stock — and that uneasy feeling sets in.
Unless you work at a business that specializes in classic or customized vehicles, or are an enthusiast yourself, often you are not going to go out of your way to attract business in that niche market. Afterall, if car counts and invoice totals are up, why rock the boat? It’s no secret that older vehicles can be more difficult to source parts for and can be more time consuming to work on. Layer that with the complexity of aftermarket components, especially on the engine management side of things, and it can be enough to scare a technician off, but it doesn’t have to be.
A Look Into the Past
There has been a specialty aftermarket almost as long as there has been an automotive industry. Adding aftermarket components to a vehicle in order for it to accelerate harder, handle better, or stop faster is nothing new or foreign to most technicians. Even swapping later model engines, or just induction systems into older vehicles is nothing revolutionary. All the way back as far as the early '90s, many a third-generation GM F-Body or C4 Corvette sacrificed their L98 powerplant and 700r4 automatic transmission for somebody’s street rod or restomod project. Though often incorporating an aftermarket harness, some programming to bypass vehicle anti-theft, tuning for any performance upgrades, and maybe removal of some unused emissions componentry, in the early days of EFI swaps the factory ECM was typically retained. This allowed not only closed loop operation, but the use of factory scan tools for retrieval of DTCs and viewing of live data if available. What they did not allow for though was a lot of flexibility.
The early days of EFI were hindered by slow processors, narrow band oxygen sensors, and the inability to truly react quickly to all the inputs coming into the controller. Instead, the ECM was relying on pre-mapped fuel and timing information in many phases of operation, such as when the vehicle neared WOT. Then there was tuning for performance adders. From simple bolt-on upgrades to larger displacement builds, even forced induction at best often involved hours of chassis dyno time where tunes had to often be burned onto removable EPROMs. Worse, if you didn’t have anyone that could program near you, it involved trial and error all while shipping the EPROM back and forth through the mail. Rudimentary technology hindered performance, limited overall power output, and sacrificed driveability. But it didn’t stay that way forever.
Technology Has Evolved
Really ramping up in the last 15 to 20 years, rapid evolutions in technology have allowed the industry to rethink the way it handled aftermarket engine management. Companies like Edelbrock, Holley, and others started developing aftermarket engine management systems that were able to allow the professional and hobbyist alike to easily install EFI into older applications. With the development of self-contained aftermarket EFI-throttle body systems that simply bolted in place of a standard 4150 style square bore carburetor, EFI installations exploded. Programming and modification for performance builds have always been there, but now the benefits of EFI could truly be scaled out to many different applications. With the installation of a suitable fuel system, a few sensor inputs, and finding reliable powers and ground, these systems are easily installed and have an incredible amount of adaptability. Eventually the popularity of swaps like the GM LS/LT platform, Dodge Hemi, and Ford Coyote pushed the aftermarket technology even further. The inclusion of sequential port fuel injection into aftermarket EFI systems and options like dual wideband air fuel ratio sensors really increased the precision at which the fueling strategy could be controlled.
One of the biggest selling points on modern aftermarket engine management systems, aside from the obvious benefits of EFI, is the ability for many modern systems to self-learn. While obviously not suited for every application, self-learning capabilities on many aftermarket EFI systems make EFI conversion more widely adaptable to enthusiasts across the industry. Aftermarket EFI companies have differing amounts of control offered to the user, but most have a self-learning capability that, with a few initial inputs when the system is set up, will allow the system an initial fuel and timing map to build off of. From there, once the vehicle reaches operating temperature, the system will constantly be adjusting the fueling strategy as the vehicle is driven through different phases of operation. The pre-programmed initial tables, plus the self-learning capabilities of these systems, generally are enough for the vehicle — even with a moderately modified engine — to have the ability to be safely street driven with good part throttle response, adequate idle, and safe wide open throttle performance. Often even more advanced levels of control and input are offered to the user who really wants to fine-tune for optimal performance.
Where Things Can Get Sticky
Any engine management system, just like any other system in a modern vehicle, regardless of OE or aftermarket, is going to assume the information it's being told is accurate. A controller takes information in and does whatever the programmed software inside it tells it to do: If inputs A, B, and C tell me this, then I will command output x to do that.
If the engine controller is either being fed inaccurate information from one of its inputs or is receiving accurate information but was set up with incorrect base programming to interpret that information in an accurate manner for the actual engine specifications in the vehicle, then an undesirable result will occur.
The amount of engine performance data available to the technician will vary by the EFI system that is installed. Most modern aftermarket EFI systems have a user interface either built into the system’s harness, or available as a tablet or phone app. That user interface is what will give the user the ability to not only monitor live data, but also log data, and in most instances allow changes to the learned data that is taking place. Some EFI systems will also allow the user to interface with a laptop to make more detailed changes, or share data logs and tuning files, but that functionality is typically not needed for basic system diagnostics. The specific data PIDs available will vary by manufacturer but the basics like loop status, desired versus actual air/fuel ratio, short- and long-term fuel trim, engine coolant temperature, intake air temperature, engine load, engine speed, fuel pressure and more, are generally available. What is at times not available are diagnostic trouble codes, so while these systems do a good job of laying out data in a manner that is easily understood, it is important for anyone working on these systems to have a firm grasp of what they are looking at. Talking with David Page, product panager, forced induction, EFI, and electronics for the Edelbrock Group, he says “Familiarize yourself with 'normal' readings from all of the sensors. Whether the system uses a laptop interface, has a handheld device or app, or has some type of dashboard, make yourself a checklist of sensors that you can monitor at key on, and then again with the engine idling, and again at whatever rpm and load point that the symptom exists at.”
Keeping Everything in Front of You
One of the biggest reasons for the popularity of aftermarket EFI is its effortless driveability in a wide variety of conditions. The reason for that ability for the system to adapt to various conditions, temperatures, and elevations so easily is its closed loop operation, just like you would see on any OE EFI system. The difference is the main concern of an OE EFI system is to get that air/fuel ratio as close to, and keep it as close to, that magical 14.7:1 stoichiometric ratio as possible — to keep the catalytic converter operating at peak efficiency. Since aftermarket EFI systems are generally not concerned with catalyst efficiency, they often allow the user to select a more advantageous target air/fuel ratio and do so across multiple phases of operation. Closed loop operation is made possible in aftermarket EFI, by a variety of inputs, but at the heart of those inputs is the wideband air/fuel ratio (AFR) sensor. The wideband sensor will sample the exhaust gases and in turn control injector pulse in order to keep the vehicle as close to the desired AFR as possible.
An Achilles' heel to these systems lies in the fact that the total fueling strategy is dependent on the accuracy of the AFR sensor being used. Unlike many modern OE systems that are fueling multiple banks, some aftermarket EFI applications, for cost and simplicity, may only use one AFR sensor. So, on an engine with multiple banks the EFI system is strategizing its fueling calculation based on information it’s getting from just one bank, and it's something the technician needs to be aware of. Under optimal conditions that doesn’t pose a problem, but if failures happen on the unmonitored bank, such as a leaking injector on a port fuel-injected EFI system. or false air leaking into an intake manifold runner, that loss of comparability can make driveability diagnostics a bit more challenging — just like the early pre-OBD II days of multi-port fuel injection.
Also, regardless of the number of sensors used, choosing an engine combination that is “friendly” to fuel injection is critical when using many self-adjusting aftermarket EFI systems. For instance, cam profiles cut on to narrow a lobe separation angle can wreak havoc on a speed density EFI setup that is self-adjusting, because of the low and inconsistent vacuum that is created. Fully tuneable systems offer a bit more flexibility in this department.
Page at Edelbrock says, “With a fully tunable speed density system like a FAST XFI 2.0 or XFI Sportsman, there are no limitations on Camshaft duration, lobe separation, or idle manifold vacuum. The tuner or calibrator simply scales all of the 3D tables according to the amount of vacuum the engine makes at idle. From here, the calibration process is no different than an engine with high idle vacuum.”
Like tackling any engine performance and driveability issue, it is important to do your research and learn exactly how the system operates. With any diagnostic process, understanding vehicle service information before starting down a diagnostic path is a key component for diagnostic success.
Another common failure in these systems is the loss of accuracy in the AFR sensor itself. A wideband AFR sensor is able to accurately determine air/fuel ratio across a much larger range than a typical narrowband sensor. Just like their narrowband sensor counterparts, a wideband AFR sensor utilizes a zirconium dioxide ceramic, however the wideband AFR incorporates a pumping cell that adds or removes oxygen to maintain a balance. It’s this addition or removal of oxygen into that cell that the ECM is monitoring to determine the AFR. Remember these sensors live in an unforgiving environment — high exhaust gas temperatures, unburned fuel, and other chemicals such as oil and coolant all degrade a sensor's accuracy over time. Wideband AFR sensors are calibrated as part of the manufacturing process in a controlled environment by utilizing the placement of a resisitor in the signal circuit to maintain a predetermined set point in each sensor manufactured. Wideband AFR sensors are extremely accurate when leaving the factory, but that accuracy diminishes over time with use. The rate of that decay in accuracy varies depending on its operating environment. While determining whether a sensor is capable of reacting to changes in exhaust gas composition is straightforward, the ability to verify the accuracy it’s maintaining that AFR at, can be a bit more challenging.
OE systems often give the technician the ability to use comparative values to infer how accurately an AFR sensor is operating. Being able to take a relational look bank-to-bank, as well as using downstream sensors to monitor catalyst operation allows the technician to gain an understanding of how "in control" the fuel system is. On an aftermarket EFI system, especially one utilizing only one AFR sensor, it’s much more difficult to determine what the ECM really believes to be true. Chances are, the whole reason you are seeing this vehicle is based around a driveability concern the owner could not figure out. Being able to compare to a known good will be instrumental in quickly and efficiently diagnosing the customer's concern. While most shops outside of those who perform engine tuning don’t have a stand-alone wideband setup, many shops do have access to a five-gas analyzer.
The five-gas analyzer gives the user detailed information about the gasses exiting the exhaust. Carbon dioxide, oxygen, carbon monoxide, hydrocarbons and nitrogen oxides are all byproducts of the combustion process, and their specific amounts present tell us a lot about how efficiently an engine is operating. While many technicians think about a five-gas analyzer in the realm of emissions testing, its ability to break down the combustion process makes it instrumental in engine performance diagnostics as well. In the instance of needing a comparative measure, a five-gas analyzer in conjunction with a lambda calculator (which can easily be found online), is a great way to measure the accuracy of the wideband AFR sensor in the system. The lambda calculator allows the technician to input the values for the carbon dioxide, oxygen, carbon monoxide, hydrocarbons and nitrogen oxides directly from the analyzer’s display into the calculator to generate a lambda reading. That reading can be used to directly compare to the vehicle and either confirm or eliminate a faulty AFR sensor diagnosis — assuming all other variables are within specification.
And lastly, making sure the aftermarket EFI system is correctly installed on the vehicle is an important but all too often overlooked step. These systems need to be installed per manufacturers' guidelines in order to operate correctly. Common errors include insufficient power sources and bad grounds.
Page from Edelbrock says, “A ground is not a ground. This is a difficult concept for newcomers to EFI systems to accept. For operating lights, electric motors like fuel pumps and fans, etc, using body or chassis grounds is fine — though still not ideal. When dealing with the signals that the ECU is sending and receiving at very high frequency, a clean dedicated ground path to the battery negative terminal is crucial. We, and most EFI manufacturers that I am familiar with, have bold, overt messages throughout all installation guides and documentation directing installers to only connect the main ground leads from the EFI harness directly to the battery negative terminal.”
If the live data you are viewing does not seem right, take a hard look at sensor placement before going further in your diagnostics. It’s not uncommon for the installer to try to locate something like a coolant temp sensor in a convenient or visually pleasing location rather than where directed by the manufacturer’s installation instructions. It might be intake air temperature sensors not installed in the right location to deliver accurate temperature information, or MAP sensors not supplied with true manifold vacuum. Or there are vacuum leaks that have not been addressed, incorrectly located air/fuel ratio sensors, or exhaust systems that leak or are not long enough to quell any fresh air reversion into the system.
Page at Edelbrock says this is an often overlooked issue. “The leak does not have to be upstream of the sensor to be a problem as the exhaust is pulsing more than you realize, pulling in a little fresh air to the sensor's gas sample.”
Slip-in collectors often don’t seal tight enough, zoomies and a turn down off the collector are not long enough, the exhaust system size, design, and condition are vital yet very often overlooked part of the equation. Just like days before when the unacquainted immediately went to making carburetor idle speed, mixture, and jetting changes at the first sign of trouble, folks today are quick to condem things like inputs, injectors, and the controller itself without doing their due diligence with the basics on the installation. Remember, Occam’s Razor principle tells us the simplest explanation is usually the right one.
The great thing about many of these systems is once the root cause of a problem has been determined, and if that issue is one of the system inputs, often times that componentry is available both through the system manufacturer as well as local parts suppliers. Many aftermarket EFI companies use off the shelf componentry that is readily available in the aftermarket. That makes servicing the problem — once the failure is diagnosed — a painless process.
The Juice Can be Worth the Squeeze
Because the benefits of EFI are numerous, the specialty aftermarket likely will continue to see considerable expansion in the realm of aftermarket EFI offerings. Because of that, availability will increase as technology and competition will continue to keep these systems priced at an affordable level.
The law of averages states that sooner or later you very well may have a customer that asks you to help keep “their baby” running smoothly so they and their loved ones can enjoy it. In business we never want to have to say “no,” and I hope that with a little bit of research and understanding you will have the confidence to tell that valued customer “yes." Because at the end of the day, the more value you can leverage toward that positive customer experience, the more likely that customer will keep coming back to you for all their automotive needs for years to come.
