I have a 1985 euro 500SEC that has been retrofitted with the cat and EHA valve. and I have spent a lot of time researching this forum to tune my car correctly to closed loop along with the perverbial intermitant high idle that seem to have started within the last 9 months. Great forum.

The current emission test is an idle and 2500 RPM back to idle. Fortunately the high idle problem did not occur at the 2 test runs. Results were high on HC and CO at idle.

HC PPM Max is 220 and CO % 1.0 max my reading were:
1rs idle 254 4.93
2500 91 .98
2nd idle 236 4.51

I thiought my timing might be off so I reset fromTDC to 10 BTDC and got vertually the same results. So I am thinking about tackling the closed loop tuning again brushing up on the posting again. I tend to think I am running a little rich.

I bought a volt ohm meter with Hz to see if I can make the adjustments.

I pugged the meter into the back of the EHA after the car was warmed up.(no #3 pin on Euro) When I first looked at the reading they were stable at about 46% (or 36%).
I thought this was great, but after about minute the readings started to bounce around 39-69 or there abouts and would not stablize. Restarting dulicated the results. I figured my meter is telling me there is a lot of adjustment going on and look for average. If I lean the car out while running I can adjust the range and figure an average will do. Interesting by making mixture richer with the 3 mm wrench, I can go to 99% and can feel the EHA not vibrating so my % must be for off.

Like to know if I am on track with this in hitting closed loop?

To add to the excitement the car decides to go into high idle 1500 RPM when I restarted it after 15-30 minutes. After about 5 minutes it dropped back to normal 700 RPM. Since I had the meter there checked the frequence across the ICV and it was like 1% (or 99%) at high idle. Basical the same a pulling the plug off. I have cleaned the ICV a couple of times trying to find out source of intermitant high idle ICV or ICU. When it dropped in RPM reading was more like 60%. I do no know if this is part of the problem emissions problem, but I think the idle control unit must be the source of the high idle because the value seems to work OK. Any help here would be apprecaite.

Thanks,

Kurt

I guess I will have to answer my own posting as I just past the emissions test and I hope I can impart some useful information to others searching this web sight that has been very helpful to me.

I used the % function of the volt ohm meter across the the freqency valve and adjusted lean/rich so it was running about 62%, (or 38% if you reverse the polarity) when it passed emissions. Timing was set at 10 BTDC.

When I was initially trying to set the % there was a wide range in the readings, but it seems they stablied after checking connections to the oil temp. sensor, O2 sensor, and water sensor. By the way the oil and water temperature sensors are normally closed when cold and open switches when at engine warm temperatures.

Even though I passed the emissions, the intermitent high idle is still lurking and fortunanlly did not materialize during the idle/2500RPM emissions test. Maybe it is curred, but I am suspect it is the idle control unit (not valve) or sensors feeding it.

Sounds like the computer was freaking out trying to react to rapidly changing readings due to bad connections. A good cross check is the voltage from the O2 sensor - you should be seeing something in the .5V range between the O2 sensor lead (not the heater leads) and ground at hot idle.

__________________
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