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#1
08-11-2003, 10:01 AM
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Finally! Stalls with Tester Hooked Up! But What Does It Mean?
FINALLY!
Took the 300E to Starbuck's this morning, with the DMM still hooked to the EHA test harness. Stopped at a light, just about after the engine reached operating temperature and felt the stumble. Drove it about a half-mile, running badly under 2000 RPM. Reached parking lot and allowed it to die, and restarted a couple of times. The change in the EHA current readings was that during the episode, they went to -2 to -4 mA, generally staying around -3. Normally at idle and driving, they have fluctuated closely around 0. My interpretation is that the coolant sensor could be bad, and is telling the control unit to richen the mix, and the oxygen sensor is picking up the richened mix and the EHA to try to lean it. Other thoughts welcome! TIA
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Chuck Taylor Falls Church VA '66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe 
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#2
08-11-2003, 04:52 PM
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What exactly are you trying to determine? Sounds like acceleration enrichment, but that is not done while driving.
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#3
08-11-2003, 04:53 PM
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Oh forgot, until the engine went up to op. temp, it would have been in open loop, ie. running rich.
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#4
08-11-2003, 05:04 PM
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My idea is that all you can tell from this data is that electronic correction isn't your problem. I would expect a lot of movement from the electronic controls in response to poor running. There isn't enough difference here to notice. That may be the only clue here. I'm not sure what to make of it though.
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Steve Brotherton Continental Imports Gainesville FL Bosch Master, ASE Master, L1 33 years MB technician
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#5
08-12-2003, 09:46 AM
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Well, I agree with that - not much useful information. You need to read this thread in the context of the problem description and the normal EHA current.
EHA Current Measurement Results - Evaluation? My hope was to catch the problem "in the act" and that the EHA's behavior would shed some light on the problem. I did test the coolant sensor and it is working perfectly. I agree with MB Doc's observation that something is telling the idle valve to shut down. I am about ready to throw in the towel and replace the OVP relay, air flow sensor, throttle switch, and decel switch. Kind of expensive (around $400), but at least then I will have a known good base of inputs to the KE control unit. You can say that this is "throwing parts" but the alternative is to drive around randomly stalling in traffic until the problem becomes consistent enough to replicate, or pay at least half of that amount for diagnostic time that might or might not find the problem.
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Chuck Taylor Falls Church VA '66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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