Secondary air system monitor3/6/2023 ![]() ![]() This promotes a safer environment by cutting down on air pollution outside. By the time fumes leave the tailpipe, there are fewer hydrocarbon pollutants in them. The pump lies after the exhaust manifold and before the catalytic converter of the vehicle and it can reduce carbon emissions by pumping fresh air from outside into the exhaust stream. This is necessary since a vehicle engine is never 100% efficient in the combustion process. The secondary air injection pump (also referred to as a smog pump or SAI pump) is responsible for lowering the number of carbon emissions that come out of the tailpipe of a vehicle. Top 5 Bad Secondary Air Injection Pump Symptoms.Secondary air ports in the combustion chamber. + Removal and cleaning of the front aluminum secondary air pipe (major job but you might be able to clean out the carbon before it accumulates) + Non-sluggish driving (regular WOT runs up to red line) + Regular replacement of the front (pre-cat) oxygen sensors (part number 11 78 1 742 050) + Regular replacement of the SAI Shut-Off Valve (supposed to prevent blowback of the exhaust) (part number 11 72 1 433 713) + Cleaning or regular replacement of the HFMs (mass air meters) (part number 13 62 1 433 566) (CRC HFM Cleaner) + Monitoring the efficiency of your cooling system (including regular replacement of your coolant temp sensor, located in the lower radiator hose) (part number 13 62 1 433 077) ![]() + Use premium fuels (the best you can find) that will burn better and not create as much carbon While carbon deposits are inevitable, there are several things you can do to delay the problem from becoming severe. It may take several years, and many tens of thousands of miles, but the design flaw of the system guarantees that it will happen again.Īny modification to the emissions system is against federal and state laws, which is probably preventing any hardware solutions to be implemented as well since any change would likely have to have BMW's approval, as well as be thoroughly tested by the federal EPA, CARB, and any other regulatory agency. Cleaning the carbon out will make the engine 'carbon free' but the problem is likely to re-occur. Repair bills can run into the thousands of dollars and weeks of down-time. Removing the carbon is a tricky process and involves disassembling the top end of the engine, pulling the cylinder heads, drilling or breaking up the carbon in multiple places, cleaning (decking) the head, replacing all of the valves and the valvetrain, along with any other customary head machining. So even though the air pump may be functioning normally, it is being blamed for the reduced air flow when it's really due to the blocked air passages.Įven if the system did not monitor the air pump flow, there would still be the problem of excessive carbon build-up in the cylinder head. Since the fault is emissions-related, it will likely prevent the car from passing a state emissions inspection test (either for the presence of the SES light or from the fault code itself). It will interpret that as a failure of the air pump, tripping a fault code, and illuminating the SES/MIL light on the dash. The M5's emissions system monitors the air flow and it will not like to see it reduced or stopped completely. With the system blocked, air ceases to flow or is dramatically reduced. The carbon is especially heavy during the engine's warm-up period when the mixture is fuel-rich. The layout and design of the system, which includes several 90-degree turns, inadvertantly encourages the carbon to build-up. Eventually each passageway and air port becomes clogged and blocked, as much as 100%. There is a shut-off valve that is designed to prevent exhaust from re-entering the system but this valve can become faulty over time and with no warning. However, normal backpressure in the exhaust forces some carbon back into the cylinder head and into the air pump system where it settles and hardens. Normally, the carbon exits the engine with the other exhaust gases through the manifolds, cats, and out the tailpipe. But this issue is different than the normal carbon build-up from inside the combustion chamber. Carbon is a by-product of the engine's combustion. The problem is that carbon builds up in the passageways for the air pump system. The system only runs for 1-2 minutes on start-up, when the car is cold (temperature based on coolant temp). As the air is heated it helps to combust the un-burned fuel coming from the engine as well as bring the catalytic converters up to operating temperature sooner. The air pump, and related air passages and tubing, is designed to pump fresh air into the exhaust system ahead of the catalytic converter. Like any modern car, the E39 M5 utilizes an air pump as part of the emissions system. E39 M5 Secondary Air Injection (Carbon Build-Up)Ĭarbon Build-Up In The E39 M5 Secondary Air Pump System (SAI). ![]()
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