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Old 10-28-2002, 01:27 PM
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190 E cold start/high idle problems

I recently purchased a 1990, 190 E 2.6 that was hard to start when cold, but ran well and re-started easily when warm. A repair shop told me the cold start problem was in the fuel distributor, and that a new one cost $3,000. I subsequently found a tech note on the web which said that almost all cold start problems are caused by the overvolt relay. I checked mine. Sure enough, the 10 amp fuze on top of the relay was blown, and when replaced the engine started easily. However, now when warm the engine won't idle., and races at about 2000 rpm with attendant neck jerk problems when you put it in gear. If I remove the fuze from the Overvolt relay while the engine is running, it settles down and idles at around 600-700 rpm. I originally thought the problem must be a bad overvolt relay, but after reading several threads in your forum, it appears that the problem may be in some other component that the relay feeds. Where do I start to look? P.S. Another fact that may be important: The auxilliary radiator fan runs constantly, and I assume the cause is a bad temp. sensor. Does this same sensor send info to the fuel system, which tells that system to up the idle?

Last edited by Orville; 10-28-2002 at 03:36 PM.
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Old 10-28-2002, 05:42 PM
Join Date: Mar 1999
Location: Tucker, Ga USA
Posts: 12,153
Sounds like the overvoltage relay is working correctly!
There are 4 sensor imputs to the fuel computer that must be correct for the car to idle correctly. Those imputs would need to be checked when the car is idling too high!
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Old 10-29-2002, 02:42 PM
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Thank you for confirming that the Overvoltage Relay seems to be working properly. Before I ask you what the other inputs are and how to check them, I need to add new information. Last night I checked the throttle linkage, and noticed that the linkage wasn't fully closing the deceleration shutoff microswitch (the one with the mini roller arm). The problem appears to be linkage corrosion and a throttle cable fitting that is broken where it screws into the L bracket. When I apply presure to the linkage with my finger, the engine idles down were it should be. I WD-40'd the linkage and added a small, weak spring to make it work until I can replace the throttle cable. The car now (1) starts easily when cold, and (2) idles properly when warmed up. I may have been looking for a high tech solution to what is basically a low-tech mechanical problem. My only concern is this: if there is nothing wrong in the electrical circuitry, why does the engine slow down and idle correctly--without any spring or finger pressure on the throttle linkage--when I pull the fuze out of the Overvoltage relay? Is my "spring fix" improperly overriding some electrial circuitry that should be checked out? Also, I'd like to know how to adress the problem of the aux. fan running at full speed all the time. Now that the engine is quite, the noize from the fan is driving me nuts. Thanks again for your help!!
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Old 10-30-2002, 02:22 AM
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Join Date: Jun 2001
Location: Houston, Texas
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I would suggest not getting into the mindset of "why this, when I do that" because you'll just go crazy. (just ask Capn') These CIS-E Jetronic fuel systems are pretty complex for their time, and as DOC stated, there are multiple sensors that relay information to the control unit.

The microswitch, although it may appear still good, may be worn out, in the sense that it takes the little arm more travel to activate the switch. I recently had idle problems and replaced mine (was $23 at dealer) and all idle problems are gone.

As far as the high aux fan problem, check the 2 pole blue temp sensor on the engine head, right side, just forward of the single pole engine temp sensor -- for a loose connection. This is an open resistance switch, so if the connection is taken off, the fans will automatically turn on high.

Good luck!
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Old 10-30-2002, 05:32 PM
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Your advice about mindset is well taken, and since no one has recoiled in horror at the prospect that I overrode delicate electronic controls with an extra spring on the linkage, I will not question the why's and wherefore's of how the injection system works. In addtion, thanks for the advice on the Aux fan. Since the connection is good, I assume that the temp sensor is bad, and I will replace it when I replace the throttle microswitch. I will report back as soon as these changes are made.
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