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Old 07-08-2002, 01:08 AM
Registered User
Join Date: May 2000
Posts: 376
Anyone ever replace a CIS computer?

I am running out of ideas on repairing my wife`s 190e 16V.

Originally the ABS light came on after I jacked the front end to balance the two front tires. I though it was an ABS wheel sensor as the left front recently failed. In hindsight, I should have known it was not the problem as the car was now stalling occassionally at stop lights. Well after I replaces the good but shredded right front wheel sensor, the light (ABS) was still lit. I had a new OVP that I had bought a while back so I swapped it and the car started right up, ran smooth and the ABS light was out. I should have stopped here.

I knew the throttle valve switch was not making contact at idle and that I had a vacuum leak somewhere. So I attempted to get at the throttle valve to replace/adjust the switch. I gave up after removing a few pieces and seeing that it was a bit more involved than I thought, but not before spraying carb cleaner down the throttle to eliminate the carbon/oil buildup. This must have caused/created a problem because after I reassembled, the car idled at 3,000 RPM!.

I finally got it down by leaning the mixture screw, but it still was messed up as it was idling rough/stalling and surging at a steady speed. I could not get it to idle right. Either rough at 1,000 RPM or smooth at 2,000 RPM. Any ideas?

I convinced myself that I had a big vacuum leak. So I removed the whole injection system, cleaned, resealed and adjusted so all the switches made corrct contact.

Well it now idles smooth at 1,800 RPM. The only way I can get it to idle lower is if I lean the mixture screw and then it runs very rough. I have checked the X11 plug #3 and I have a steady 50.7% duty cycle. Not moving. I have a fault somewhere. Any ideas where this could be? I have checked the O2 sensor (reading lean 0.25v at idle but fluctuates and its heat element is in spec.) the EHA is attempting to correct and if I pass a volt through my body at the O2 sensor the car leans out and dies. The air/idle valve has voltage but is reading between 500 to 350 ma when rough and 225ma when smooth. I can get it to run smoother if I slightly depress the air flow meter (richening) while running. But this causes it to stay at an elevated 1,800 RPM. If I unplug the OVP relay while its running at 1,800 nothing changes, but when I plug it back in it pulls the RPM down and it runs rough. EHA goes to 1.2 ma when I do this and then jumps to -3.6 ma when I depress the air flow meter. This appears to be out of spec? The air flow meter values appear to be at spec.

To summarize, it will idle smooth at 1,800 but not at 1,000 no matter how much I play with the mixture setting and it is less than 1/8 of a turn between these two extremes.

Where does one start to look when encountering the fixed duty cycle at the X11 plug?

I apologize for the long post, but I am almost at my wit ends.

Thank you for any feedback.

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Old 07-08-2002, 05:50 AM
zee's Avatar
zee zee is offline
Registered User
Join Date: Aug 2001
Location: Chennai,India
Posts: 28
Hi Tinker,
I have had all those symptoms u had mentioned in my 200TE. My mechanics tried to cure it for about 5 weeks & finally it all boiled down to faulty ECU.
I tried getting one locally (India) and found out the price to around USD1800, tried Srilank ,the price was USD1500 approx.Singapore & Malaysia had no stock,price not given,had to place order.Since I didnt have much time to wait there ,I did not place order with them

Finally I found one used piece with 2 blown capacitors, in Dubai UAE, for an unbeliviable USD 69.Bought it ,changed the capacitors.
Now the car is back on the road.Hope this might be of some academic interest.
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Anyone ever replace a CIS computer?-ecu.jpg  
1990 220TE
1988 300GD
1989 yamaha V-MAX(sold)
1993 BMW R100R
1956 Willys Jeep(low bonnet)
1982 Honda XL 250
1987 300D
1994 toyota surf (4runner)2.4 TD EFI
1953 Land Rover
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Old 07-08-2002, 05:59 PM
Registered User
Join Date: Jan 2002
Location: England
Posts: 1,841
Make sure no live wires touched the ECU - that happened to me and my ABS ECU was fried. It went loopy and was driving the abs pump all the time the ignition was on (not good).

But as the problem seems to have been caused by you (sorry!) I doubt that's it. If you run out of ideas, a decent tech will be able to solve it quickly, unless anything is actually broken.

2.5-16v 1990 90,000m Astral Silver
2.0E 8v 1986 107,000m Black 2nd owner
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