Hi,
have found time to play about with my 16v Cosworth and will relay my results to all you that have 16v tickover problems.
Since getting the vehicle it has always suffered the "uneven tickover problem".......never a constant tickover, usualy too high.Looking at various websites for 16v's the consensus is "they all do that...just live with it!".
Thought, when I had the time, and inclination, would look into it.This is what I did.
Firstly, I took off the air flow housing (complete) to get access to the throttle valve body underneath.
After removing the the throttle valve body, gave the inside a good clean......actualy, wasn't that dirty!.Bolted body back on inlet manifold, (has it's own gasket, unlike a 190e).
Cleaned inside the underside of the airflow housing....gave it a good flushing with WD40.
Whilst i had the airflow housing off the vehicle, I took out the 4 small screws that hold the potentiometer housing to the airflow housing to get access to the potentiometer underneath. I gently cleaned the surface with WD40 on a cotton bud.Put back the cover in the same position it came off.
Put everything back on the vehicle.
Connected the adjustable rod to the throttle body (actuates accelaration) just as I had removed it.Checked the throttle switch was working ok with a continuity meter....... had to adjust the rod slightly to get the right reading at idle (throttle valve shut) position.
I checked everything was back as it should, and lastly connected the throttle cable and made sure it was adjusted to spec.
This is the interesting part.
I found that at rest (idle), the throttle valve microswitch was bearly being activated by sheet metal lever on the throttle mechanism.The movement between the microswitch being activated or not was so small that sometimes you could hear it click and the next time it wouldn't.The lever is pulled downwards by a spring at idle and the spring was in place doing its job.The microswitch was working but not being activated everytime the throttle was at idle..........this being so, the ecu is being fed wrong information ie. it is being told that the car is off idle, when in fact the car is not moving!.( i can only guess that that ecu is trying to compensate for the information it is being given and making the tickover erratic).
I looked everywhere on the throttle side of the fuel injection mechanism for an adjustment or signs of wear......and could find none.
My remedy.....MB will hold their heads in their hands....was to take off the sheet metal lever and file a very, (very), small amount of metal to elongate the runner where a small circular plastic roller activates the throttle movement.This lowers the lever just enough so you can see and hear the microswitch being activated every time.
Put everything back, checked, started car.......ticks over, rock steady , just a shade under 1000rpm.(there is a rotory adjustment on the end of the idle speed control ( which MB never refer to in their manuals) which i believe can be used to fine tune the idle....but don't quote me on that!
Well all that above sorted my car out...hope it may help someone else out!
Best of luck Ron
have found time to play about with my 16v Cosworth and will relay my results to all you that have 16v tickover problems.
Since getting the vehicle it has always suffered the "uneven tickover problem".......never a constant tickover, usualy too high.Looking at various websites for 16v's the consensus is "they all do that...just live with it!".
Thought, when I had the time, and inclination, would look into it.This is what I did.
Firstly, I took off the air flow housing (complete) to get access to the throttle valve body underneath.
After removing the the throttle valve body, gave the inside a good clean......actualy, wasn't that dirty!.Bolted body back on inlet manifold, (has it's own gasket, unlike a 190e).
Cleaned inside the underside of the airflow housing....gave it a good flushing with WD40.
Whilst i had the airflow housing off the vehicle, I took out the 4 small screws that hold the potentiometer housing to the airflow housing to get access to the potentiometer underneath. I gently cleaned the surface with WD40 on a cotton bud.Put back the cover in the same position it came off.
Put everything back on the vehicle.
Connected the adjustable rod to the throttle body (actuates accelaration) just as I had removed it.Checked the throttle switch was working ok with a continuity meter....... had to adjust the rod slightly to get the right reading at idle (throttle valve shut) position.
I checked everything was back as it should, and lastly connected the throttle cable and made sure it was adjusted to spec.
This is the interesting part.
I found that at rest (idle), the throttle valve microswitch was bearly being activated by sheet metal lever on the throttle mechanism.The movement between the microswitch being activated or not was so small that sometimes you could hear it click and the next time it wouldn't.The lever is pulled downwards by a spring at idle and the spring was in place doing its job.The microswitch was working but not being activated everytime the throttle was at idle..........this being so, the ecu is being fed wrong information ie. it is being told that the car is off idle, when in fact the car is not moving!.( i can only guess that that ecu is trying to compensate for the information it is being given and making the tickover erratic).
I looked everywhere on the throttle side of the fuel injection mechanism for an adjustment or signs of wear......and could find none.
My remedy.....MB will hold their heads in their hands....was to take off the sheet metal lever and file a very, (very), small amount of metal to elongate the runner where a small circular plastic roller activates the throttle movement.This lowers the lever just enough so you can see and hear the microswitch being activated every time.
Put everything back, checked, started car.......ticks over, rock steady , just a shade under 1000rpm.(there is a rotory adjustment on the end of the idle speed control ( which MB never refer to in their manuals) which i believe can be used to fine tune the idle....but don't quote me on that!
Well all that above sorted my car out...hope it may help someone else out!
Best of luck Ron
