Author: Michael McCoy

If your BMW was manufactured between the late 1980’s and 1995, you should be able to pull diagnostic codes out of the car via the check engine light.

To read these codes, turn the key to position two (run), but do not start the engine. Within 3 seconds of turning the key to position 2, you will need to stomp the gas pedal from idle (not touching the pedal) to WOT (wide open throttle, to the floor) and back, 5 times. If you successfully do this within the 3 second window, the check engine light will turn off, then a long on, then off again, and then begin flashing the codes out to you. If there are no stored codes, it will still flash something out, as there is a code for that too. If you get a constant lit CEL, turn the ignition off and try again.

The code for “no codes stored” is 1444, which would be presented as on-off-on-on-on-on-off-on-on-on-on-off-on-on-on-on-off-on-on-on-on followed by a long off, a long on, and then repeating.

The primary control of boost in a turbocharged system will be the wastegate. The purpose of the wastegate is to bypass the turbochargers turbine, reducing its ability to make boost. (For more information on how the turbocharger works, see our article on turbochargers.)

The wastegate will have a pre-set spring pressure. This can be adjusted by changing the spring on most, and also by varying the preload of that spring in some others. Outside of that, a boost controller can be used.

Boost controllers come in a variety of different types, however, there are only two methods for raising the delivered boost; you must either reduce the pressure on the bottom port of the wastegate, or add pressure to the top port (if available) on the wastegate.

For reducing the pressure on the lower port on the wastegate, there are two popular methods. One is a “controlled bleed”. This is found in mechanical boost controllers that are “needle type” valves, as well as the method used by some electronic boost controllers by pulsing a solenoid to control the amount that is bled off. The other is to artificially hide the boost signal from the wastegate until an alternate target boost is reached, as is done mechanically with a “ball and spring check valve”. Some electronic boost controllers use this method as well. Some electronic controllers also will blend between the two, hiding the boost from the wastegate until a target pressure is reached, and then acting like a controlled bleed once that target is reached.

Both of the above are common implementations using only the lower port on the wastegate. The top port is also very useful in that you can leave the bottom port unmolested, and add pressure to the top port only when more boost is desired. Usually this is only something that electronic boost controllers will use, but some mechanical boost controllers also take advantage of this port.

On electronic vs manual controllers, it strongly depends on which versus which. In general, electronic controllers have an advantage of being able to react in a non-purely-mechanical means. So if you have a mechanical system that becomes inefficient and tapers at higher RPM, some electronic systems give you the ability to compensate and command more boost at higher RPMs. Mechanical systems tend to only be able to translate the natural boost curve up, but not drastically alter its shape.

If you own a BMW manufactured after the 1970’s, there is some sort of computer controlling the fuel delivery to the engine. By the 1980’s all of the BMW cars in the US had some sort of fuel and spark control based on a piece of electronics. This computer would use various load inputs, such as throttle position and air flow measurements, to determine how much fuel is needed. It would also use that data to determine the best time to fire the spark plug. As the engines became more sophisticated, so did the computers controlling them.

Engine oil gets contaminated over time by moisture, fuel, and particulate matter.

Moisture generally being introduced as a byproduct of combustion, it is easily burned off by getting the oil up to temp. If you have a short commute, it is a good idea to take a long drive at least once a month in an effort to get the oil to a more reasonable temperature.

Fuel contamination is generally a result of cold starts. We generally gauge the life of the oil and the change interval based on mileage, but most of the degradation and contamination of the oil with short commute vehicles is a function of cold starts. It is best to crank the car and start driving immediately. This will cut down on the warm-up time and reduce the total contamination from the cold start event.

Particulate matter in the oil gets there one of two ways. The first is via the air filter. The air needs to be as clean as possible going into the engine. The fine particulate can cause engine wear. The oil filter will catch a lot of it eventually, but that may be after it has spent some time on the side of the cylinders causing wear. We recommend either paper filters or multi-layer foam such as is found in our intake kit. The other particulate matter in the oil is generally a function of the wear. This will be ring material, cylinder material, and possibly bearing material. Some wear is normal over time, especially on cold starts when the parts of the engine are not their ideal shape or size. Catching some of that wearing material before it gets run through the oil pump can help reduce some of the secondary effects, so a magnetic oil drain plug is a good idea.

An appropriate oil change interval with a suitable oil will be the best way to prolong the life of your engine. Not every application is the same, so it is a good idea to consult with experts regarding your particular needs. Collecting an oil sample and sending it off for analysis is a great way to see if you need more (or less) frequent oil changes as well as keeping an eye on what is going on with your motor over time.

It is becoming common to blend Ethanol with Gasoline in many states. Most stop at 10%, but there have been cases where higher concentrations of Ethanol has been found in pump fuels.

Ethanol by itself is not bad. E85 (75-90% Ethanol, the rest Gasoline), if you have a readily available supply, can be great low cost high octane fuel.

The downside to ethanol, especially in low ratios such as E10, is that you do not get any of the benefit of ethanol’s high octane rating. You do get its cleaning properties though, and that is where the trouble begins. Ethanol will clean off the varnish and other deposits in your fuel tank and fuel system. Usually (hopefully) this is caught in the fuel filter. It is not uncommon for fuel filters to be come clogged very quickly as the switch to fuels containing ethanol is made. The good news is that this is not a perpetual case. The “dirty” stuff will be cleared out fairly quickly and it may only take killing a handful of filters before the change interval can return to normal.

The other potential problem is compatibility with the fuel system. Modern fuel systems should all take 10% ethanol fairly easily. It will speed up the deterioration of  older fuel lines, and it is always a good idea to replace all of the soft lines on the fuel system with some frequency.

E85 as a fuel is a lot harder on the fuel system than E10. You will need Viton or similarly chemical resistant fuel lines installed. You will also need a larger capacity fuel pump and larger injectors, as it will take approximately 30% more fuel to make the same power.

There are a number of common problem areas on the turbocharged (and some supercharged) M50 based motors.

With the OBD1 throttle body, there is a port on the bottom for the purge valve. It is generally best to disconnect this from the purge valve solenoid and cap the port on the throttle body, or install a check valve between the port and the solenoid.

On the M50 manifold, the ICV connector that connects the “turkey neck” to the intake manifold is held in with one clip. Under pressure, the connector can rock on its mount and compromise the o-ring seal. This can be especially difficult to find/troubleshoot as it often will snap back in place when the engine returns to vacuum based operation. The two common solutions are to either glue the fitting into the intake manifold, or to use zip ties to hold the fitting in the manifold.

In some cases the crankcase ventilation system will have been left connected to the intake manifold. This should not be the case. The crankcase must be vented to a non-pressurized location. On early M50 based applications, there is a small hose that, in stock form, connects the valve cover to the throttle body boot. That must be vented elsewhere. (We recommend connecting to a catch can, and then to a crankcase evac kit tied into the exhaust.) There is also a small hose that connects the valve cover to the ICV connector mentioned above. That should be plugged on the valve cover side, and plugged on the ICV connector side as well.