16v tickover problem solved.

RonH

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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
 

television

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Ron I put up what you have done 10 times and told folk to file the stop so that it closes but no one listened.

Yes as you say it does not switch over to the idle ECE and goes to high

Good work :D:D
 
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RonH

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Hi Television,
wish i'd known earlier, could have saved some time.

One "so called" MB expert, on an American site, says MOST tickover problems are potentiometer related...that threw me.
The Bosch Fuel Injection Book says, "KE potetiometers measure the position of the sensor plate. The only purpose of this is to provide information for enrichment during cold acceleration.If you engine stumbles during cold acceleration, the potentiometer may be bad or out of adjustment ".

With such advice out there, there must be a lot of money being needlessly wasted.

Cannot believe that such a simple modification can make so much differance!.


All the best.......Ron.
 

television

Always remembered RIP
Joined
Mar 14, 2005
Messages
164,073
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331
Age
86
Location
Daventry
Your Mercedes
2002 SL500, 216 CL500, all fully loaded
Hi Television,
wish i'd known earlier, could have saved some time.

One "so called" MB expert, on an American site, says MOST tickover problems are potentiometer related...that threw me.
The Bosch Fuel Injection Book says, "KE potetiometers measure the position of the sensor plate. The only purpose of this is to provide information for enrichment during cold acceleration.If you engine stumbles during cold acceleration, the potentiometer may be bad or out of adjustment ".

With such advice out there, there must be a lot of money being needlessly wasted.

Cannot believe that such a simple modification can make so much differance!.


All the best.......Ron.

Hi Ron. I read about this from one of the best diagnosis guys in the UK ,it was on an early 202 C180 and being an auto it made it hard to drive, and I put it up but no one took it on board

Perhaps an easy test would be to take off the plug and link the wires in the plug, if the revs drop then thats it.

I am going to ask that your post be put into the DIY section as this is a common problem
 

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