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#1
08-22-2010, 09:43 PM
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EHA Valve Adjustment question
OK...I adjusted the EHA valve on my w124 a quarter turn CW to alleviate the long crank starting issue. It did work and started easier but it had to chug, chug, chug and then I had to give it gas and warm it up for a while. I figured this was not a good sign so I adjusted it 1/8th turn back. Now, it's back to a long first crank but when it starts it's idling better until it gets over 90 Degrees (everything is fine from about 82 to 89 degrees) and then it struggles a bit while in gear. Adjusted air mixture to best setting I could get. It's ok but not great. Anyone know why this happens and what part the EHA plays in the fuel delivery while idling? I've changed every sensor except for the air intake and since it acts up when the thermostat gets over 90 I figured this could possibly impact the idle with it's signals. Of course, when she runs down the road, there is no problem. Also, today, I took off and cleaned out the idle control valve and it looked pretty clean as it was and worked when I tested it with ignition turned on. Have new O2, non resistant plugs, new cap, rotor, coil, water temp sensor, and OVP.
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#4
08-23-2010, 02:44 AM
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Quote:
a. It only costs €12 from Mercedes. b. It takes 45 seconds to install. c. In my case, it resulted in an almost complete solution to hot idling issues. Either that or measure its resistance at various temperatures to ensure it conforms to specification. If not, splash out that €12. Again, in my case, the duty cycle shot up from 50% +- to around 92 when the new air temperature sensor was installed. I adjusted it back to 50% +-. Good luck to you. RayH
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#6
08-23-2010, 12:13 PM
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SPTT, the EHA is apparantly a pretty strange animal, after reading years of coments about it here. But, to understand it a bit better, I would recommend 3 things:
1. Pull down copies of some of the master techs' articles from the archives herein on adjusting and monitoring the CIS system. I think Steve Brotherton wrote a great one. 2. Buy a little $30 Sears multimeter (#82139 or similar) that has current reading capabiity and duty cycle capability. Read the instructions carefully. 3. Build a simple little 2-wire harness to interface the meter into the EHA circuit, so you can check the current during start and run. 4. Use the duty cycle meter in pins 2 & 3 of the round diagnostic connector on the fender well to check the idle lamda numbers. These two bits of info will help you really understand what the system is doing, and when. Then, if you want to verify, as stated above, you may need to get a pressure gauge set for the upper/lower chamber pressure. I found one on eBay a few years back for under $30. Of course (the disclaimer) I've played with all these toys for years trying to remedy my heat soak starting problem to no avail. DG
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#7
08-23-2010, 01:19 PM
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[Q
TI've played with all these toys for years trying to remedy my heat soak starting problem to no avail. DG[/QUOTE] i am very satisfied with the exhaust heat wrap installed on my 300se. The under hood temperature dropped dramatically and better cooling inside . mak
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#8
08-24-2010, 12:20 AM
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Well guys, I played with the Lambda and richened it up last night. Starts on first crank. Doesn't idle well 'til warmed up to around 76-80 Degrees then everything is fine. Acceleration from stop/idle was strong, ran well in 100+ degree weather for 90 miles to work and back. Started up fine every time. I guess I compensated enough for it but will it pass smog if needed???...probably not
 I'll check the duty cycle thing when I get a chance to get one of those meters. Will be good to learn and I'm very familiar with electronics and repairing and testing them...but you have to have the right equipment to test! I know someone's been in that fuel distribution system before but it did pass smog when I bought it.
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