hi guys and gals,ive been having serious issues with the e.h.a operating system,in the cold when engine sits all night the engine will not start,when i connect the 2 pin connector to eha the car starts and idles to approx 1,000 r.p.m,problem is if i gas the peddle she idles up to 2,000 r.p.m then about stalls out then catches and repeatedly idles up and down between 1,00 r.p.m and 3,000 r.p.m untill full 80 celcius operating temp is achieved,if i attempt to drive the car it bogs down goes absolutley nowhere revs up to 4,000 r.pm, will not shift into second gear until i lift the gas peddle up,now if i disconnect the 2 pin sensor the car idles and runs great,however there is still a lack of full power especially on freeway.this is what i need to do,in the morning i must connect eha sensor to start car let it warm about 5 mins,then in order to drive car functionaly i must then disconnect sensor.i was told from the foriegn auto shop i needed to replace both fuel pumps so i installed high flow systems fuel pumps,operating at a greater psi than stock,i replaced fuel filter,02 sensor,ovp.and it never fixed issue,does anyone have any idea as to why this eha system is operating backwards the air fuel ratio was adjusted because it had a surging idle,i just cant take opening the hood every freezing morning to connect eha then disconnect it,then when engine is ice cold reconnect eha to start it again,any ideas would be awesome,thanks.marc

Have you replaced the EHA valve?

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1989 300CE

Sounds like possibly just a mis-adjustment of the basic fuel mixture.

Do you have a volt meter with duty cycle OR amp reading capabilities?

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MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

yes i purchased a used E.H.A on ebay for $70.00 i adjusted air fuel ratio,wich took away surging idle,unfortunatley i dont have any tech tools right now,i had to sell off most of my high end tools booohoo. when i first got the car my mechanic told me to replace both fuel pumps,the fuel filter,the o2 wich i did,he said it would solve the issue,i wonder where he learned his mechanical info,i could have told him that,it didnt help.i think your right it may be the fuel mix,im going to send it back in the shop because i cannot possibly figure this issue out,they had better come up with a better diag this time.i will tell him to recheck air fuel mix,it idles at about 650 rpm,it seems kinda low to me.i feel a slack when i floor it on freeway its just not all there.

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enjoy life,take the coal that is handed to you and turn it into diamonds. { PHILLIPIANS 4:13}

Mechanics who only have a scant knowledge of Mercedes or the CIS injection system tend to approach problems with the slash and burn technique - i.e. strat replacing parts until we find a solution.
It's better off taking time out and finding an Indie shop who have great experience with M.B.'s

Having said that most. Indies around my area send CIS and later similar injection systems cars off to a Bosch Fuel injection specialist rather than try and mess around with them themselves.

You are better off getting some pointers from on a forum like this than taking your car to a mechanic who will just throw expensive spare parts at a problem.

There is an excellent Bosch Fuel Injection book that I have found very useful. It covers both CIS and Motronic systems. It is around $20 on Amazon and offers a wealth of information that I'm sure many shops don't know...

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1989 300CE

i may have to pick up that book for myself,this place i bring the car to is a german mercedes and bmw only shop,i would like to think he knows what hes doing,but just cuz they specialize on a certain car dont mean they know what there doing,lol!!,im gonna rub it in to him how he told me to replace all that stuff,wich im sure couldnt have hurt it since they were all 21 years old anyway.

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enjoy life,take the coal that is handed to you and turn it into diamonds. { PHILLIPIANS 4:13}

The used EHA valve you purchased could be defective. They do go bad with age. As others have stated, it does sound like your mixture is needing adjustment. I know how you feel with the so called "specialists". If you read that book cover to cover I bet you'll show them. Below is the link for the book from Amazon.

http://www.amazon.ca/Bosch-Fuel-Injection-Engine-Management/dp/0837603005/ref=sr_1_1?ie=UTF8&s=books&qid=1293775377&sr=8-1-spell

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1989 300CE

thats very assuring thanks for all your input mbzman,much appreciated.

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enjoy life,take the coal that is handed to you and turn it into diamonds. { PHILLIPIANS 4:13}

i just ordered the book,used in like new condition,for $15.00 $8.00 shipping from some book store in canada,im sure i will find usefull info in it,i like the part where it says high performance tuning.

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enjoy life,take the coal that is handed to you and turn it into diamonds. { PHILLIPIANS 4:13}