There are currently three or four 95/94 E320’s in this forum experiencing the same problem under the same conditions.
I keep hearing the voice of a tech a few years back, when the ignition lock failed on my 260E. He said, “The 89’s are starting to go,” in reference to a sudden increase in 89 E-Class ignition tumblers he had to replace. I wonder if there is some component on 94/95 E320’s that is also “starting to go” and causing these ASR faults….
FYI: In every single post I have read on MercedesShop, in which the throttle actuator was replaced, it did
not solve the problem, so you can probably put away your checkbook.
My ASR issue is also temperature related and for a long time I suspected it was the coolant temperature sensor, but that never made sense – and still does not. But on a bitterly cold day this past January I drove from VA to DE (low 20’s outside) and the effect of 20-degree air being rammed into the radiator at 80+ MPH apparently affected the CTS enough to keep the car in so-called limp mode for the entire trip. (So-called because at 80+ I was hardly limping.) Only when I exited in DE, and my speed dropped to about 60 on a local road, did the sensor apparently send a “good” signal that released the ASR fault condition.
I have researched this a lot, reading all the opinions of the causes, but the bottom line is my ASR fault occurs when the coolant temp sensor is cold, and goes away after it warms up. The fact that my fuel economy is down a bit and I can often smell harsh fumes when hot idling lends further credence to a faulty coolant sensor. That sensor is perhaps the most weather-exposed electrical component under the hood, sitting right up front, just behind the grille, where cold breezes and moisture can easily find it. Indeed, my ASR faults most frequently occur(ed) on cold & windy and, especially, cold/\windy & wet days either after the car was sitting overnight, or, when bone-chilling cold, after sitting for a few hours. The behavior is always the same:
Strong crank and normal initial idle speed. Touch accelerator and there is an RPM surge for a few seconds (or longer), then a relay in the back seat area pings, ASR light illuminates, and rpm drops to about 500. Interestingly, tapping the brake pedal can stop the surge and immediately trigger the relay ping/ASR/low idle. However, if I do not touch the accelerate after startup, and simply use the car’s traction to back out, and move forward, applying the brake will not trigger the ASR fault. Only after I travel a bit and then use the accelerator will that occur.
(This points to Accelerator switch.)
This fault cycle will happen repeatedly until the coolant temperature reaches, and remains, at 82C. (There is a false-positive interval when temp reaches 82, then drops back to 80 as the thermostat opens. After a few more minutes, temp reaches 82 and stays there.)
My current planned course of action is to replace the coolant sensor, since I need to do that regardless. Then the brake switch, and the accelerator micro-switch (if I can actually find it).
Below are links to possible solutions per the experiences of the members and expert techs here. As you will see, none of them say anything about coolant temp, obviously because it makes no sense. But it appears to be involved nonetheless. Hope everything works out for you.
ignition switch
http://www.peachparts.com/shopforum/showthread.php?t=28514&highlight=e320+ASR
Tire Inflation
http://www.peachparts.com/shopforum/showthread.php?t=61476&highlight=e320+ASR
fuel system control unit
http://www.peachparts.com/shopforum/showthread.php?t=61476&highlight=e320+ASR
base module
http://www.peachparts.com/shopforum/showthread.php?t=61476&highlight=e320+ASR
The Elusive Throttle Safety/Micro Switch.
http://www.peachparts.com/shopforum/showthread.php?t=61476&highlight=e320+ASR
http://www.peachparts.com/shopforum/showthread.php?t=114906&highlight=e320+ASR
http://www.peachparts.com/shopforum/showthread.php?t=84223&highlight=voltage+regulator
Brake/Stop Light Switch
http://www.peachparts.com/shopforum/showthread.php?t=84265&highlight=e320+ASR
http://www.peachparts.com/shopforum/showthread.php?t=133918&highlight=e320+ASR
http://www.peachparts.com/shopforum/showthread.php?t=204365&highlight=e320+ASR
http://www.peachparts.com/shopforum/showthread.php?t=188665&highlight=e320+ASR
http://www.peachparts.com/shopforum/showthread.php?t=164241&highlight=e320+ASR
http://www.peachparts.com/shopforum/showthread.php?t=164241&highlight=e320+ASR&page=2
Wheel Speed Sensor
http://www.peachparts.com/shopforum/showthread.php?t=108466&highlight=e320+ASR
Voltage Regulator -- (I Still Need to Check This)
(MSG # 20)
http://www.peachparts.com/shopforum/showthread.php?t=105682&highlight=e320+ASR&page=2
Water In Electronics/Control Units
http://www.peachparts.com/shopforum/showthread.php?t=209356&highlight=e320+ASR
(MSG # 21)
http://www.peachparts.com/shopforum/showthread.php?t=105682&highlight=e320+ASR&page=2
OVP
(MSG #58)
http://www.peachparts.com/shopforum/showthread.php?t=188665&highlight=e320+ASR&page=4
(Oh, and MSG# 59 is, um, amusing.)
Related Threads/Comments Worth Noting
http://www.peachparts.com/shopforum/showthread.php?t=108761&highlight=e320+ASR
The below thread is very interesting since that area my car had become exposed to rainwater around the same time my ASR issues began:
(MSG #15)
http://www.peachparts.com/shopforum/showthread.php?t=164083&highlight=e320+ASR
“..ea/cc/isc has own computer in pass side floor …”
Finally, in these threads ETA’s were successfully replaced “just because,” and with no mention of ASR problems.
http://www.peachparts.com/shopforum/showthread.php?t=204530&highlight=e320+ASR
http://www.peachparts.com/shopforum/showthread.php?t=147929&highlight=e320+ASR