W124 230E hard starts and occassional idling woes

[124Addict]

I hope you'll bear with me but my problem goes like this:

About three months ago, I had a local shop, who does only mercedes benz's, repair my long-running problem with the oil leak and noisy vibrations caused by a bracket connected to the airconditioning compressor. They installed new oil seals and removed all broken bolts of the bracket and replaced it with a new and sturdier type. This were all done with the engine out of the engine bay. After, all were done, they returned the engine and did the regular oil change and tune-up.

The repair was well done since no leaks and noisy vibrations ever recurred after that.

However, I suddently developed a hard starting problem. I returned it to the repair shop and they adjusted fuel and air mixture, etc., and somehow concluded that my starter is failing. It soon did fail and I immediately replaced it.

The replacement cured the hard starting but it returned after a week. Next I had the injectors cleaned. That was fine but the hard starting returned. To save the effort and money, I just adjusted my style and started the engine while softly pressing on the gas pedal. That was fine for a while. Last November, my aux fan relay got burnt. That was replaced, but electricity seemed to fluctuate. Tapped the OVP and secured the new relay upon the advise of my electrician. It worked.

One December morning, apart from the hard starts, I suddenly encountered, a very rough idle at start up. So rough that the engine will cut off whenever I turn on the airconditioning or release the gas pedal. This somewhat normalizes when the engine gets warm. I say somewhat, because it is still not a perfect idle because there's an occassional shudder that I feel. Cruising, though is not a problem.

I sent this to another shop (mercedes benz only) for tune-up. They changed the spark plug and adjusted fuel and air mixture. They cannot get the idling to run perfectly as it should. They came up with the conclusion that the control unit should be replaced by putting another unit.

Because it was expensive, I tried to get a second opinion. I found a shop who said they can diagnose a bad or good control unit. They did not see anything wrong with it. I don't know if I was glad to know that there's nothing wrong or was just glad that they said what I wanted to hear. They did, however, cure my stumbling idle at start up by increasing idle speed which the previous shop said they cannot adjust because of the control unit. But there is still the hard starts and occassional shudder even when the engine in under normal operating temp. They said that the occasssional shudder might be the engine support. But I replaced this about 3 years ago. Do engine supports fail within that period?

This is still bearable but can anyone please point me in the right direction. If it is indeed the control unit (ouch!!), there goes my money for the paint job. I've checked the OVP and the fuse seems fine. I've read, though, that they can fail internally. I'm not a technical person. so an explanation on what my problem (causes/solutions) in layman's terms will be appreciated.

[autozen]

We don't have any 230Es over here so I'm going to guess that it is the same basic setup as the 190E 2.3. If the setups are the same, the first shop was right about idle not being adjustable. What the second shop probably did was put restrictors or openings in the idle circuit to bypass the idle air valve. If you do a search, we have had discussions about this problem. I don't think there is aproblem in your control unit. Members here are suspecting the idle air valves to be either getting sticky or failing electrically. I always have trouble with the search, but try looking for idle air valve or idle air management system.

Good luck,
Peter

[autozen]

An additional thought. When you have the hard start, remove the air cleaner, remove the connector from the idle air valve and apply 12 volts to the valve. If the var starts, you know you are barking up the rigth tree.

Peter

[schumi]

I would first replace the distributor cap and rotor unless they have been replaced in last 30k miles or so. It sounds like your mechanic may have already done the EHA adjustment, but if not I would try that (do a search for EHA and you'll see what I mean). I would also look at this link:

http://www.mbca.org/pages/tech/MBCA_Rough_starting.htm

[124Addict]

Dear Autozen,

Yes, I think this is basically the same set-up as the 190E 2.3 with the 102 engine. What do you mean by idle air valve, is this the same as idle contol valve resting beneath the air cleaner? If this is the same, I replaced this about 2.5 years ago. Before that time my idle surges above 10 and sometimes goes down to less than 5. And yes, there was that occassional hard starts also. This was cured as soon as it was replaced. Will it necessarily fail within that time frame? I've read that cleaning it with carb cleaners can be an alternative. Would you agree?

Dear Schumi,

I like your name. It reminds me that the F1 2005 season is about to start. I've already replaced the distributor cap and wires 3 years ago. And yes, I think it was the EHA that they adjusted (below the air cleaner). I've read the link that you've mentioned before. However, I'm not sure if this is what I would like to do in the meantime given that it cover-ups the problem. Rest assured, that upon exhausting all possible remedies, I'll definitely give this a try.

Thanks to both of you. I'll keep you posted if there are any developments.

[124Addict]

Last Saturday, as recommended, I cleansed the idle control valve with carb cleaners and was able to dislodge a lot of dirt inside. Reconnected it and while the air cleaner was off, I tried to start the engine. That did not solve the hard starting. What surprised me however, was that the throttle valve kept on moving erratically (closing and opening) while idling. If I recall it right, it should not open at all while idling. I disconnected the CIS-E control unit and the throttle valve stopped moving. Kept it disconnected and used the car that day without any problems. In the evening, I took out the control unit, OVP, and another relay with some German name on it "Kalstart". Opened everything and sprayed it with a contact cleaner that I just bought and reconnected everything back.

I don't know if that solved the problem, because I did not take another look at the throttle valve.

But what I'd like to know is what causes the throttle valve to act that way? I'm tending to believe that the control unit is my main problem since my idling somewhat smoothed out when it was not connected.

I would appreciated anyones help, pleeease!!!!