When we service your American RV at LAS Motorhomes we check the exhaust emissions if your vehicle runs on either LPG or petrol.
Just recently the VOSA MOT standard has tightened up their tolerances on certain items, one of those items is the exhaust emissions.
Whilst checking the emissions on each MOT and service inspection we have found that to match the required standard has become more difficult.
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The petrol engine uses an oxygen sensor which will measure the air/fuel mixture ratio. If the exhaust emissions are too high the engines computer will shorten the time that the petrol injector is open thus altering the emissions. When the emissions are too low the engine computer will lengthen the time that the injectors are open. This is how the lumber is controlled, this also affects the CO produced from the exhaust and the unburnt fuel that is emitted from the exhaust.
In some cases what is happening is if a motorhome has been running on LPG for a considerable length of time and the emissions are not very close to the petrol emissions the catalytic converter is being affected and the CO reading becomes too high.
A high proportion of American RV Motorhomes have only got low mileage and we have found their engine timing chains are becoming a serious issue.
In the example below the engine has covered 42,000 miles, as you can see from the pictures the chain is very loose and once the chain has been replaced the emissions come back to their correct level.
One way to test the timing chain is to rotate the engine by hand in the direction of rotation, then turn the engine backwards by hand while someone watches the rotor arm. The engine should only move a fraction before the rotor arm moves, if this is the case then the timing chain is serviceable.
If the timing chain is stretched to the extent that you can see in the images then the engines valve trimming is badly affected, this will delay the opening of the valves which will affect the engines emissions.