95 E320 ASR problem - please help - PeachParts Mercedes-Benz Forum

amg280 · #1 09-21-2008, 10:57 PM

1995 E320, 198K, runs great except for an ASR issue I am having.

While acceleration hard, the ASR warning triangle lights up and cuts my power, and even applies the back brakes. It will usually do it from 50mph up with spirited acceleration. Also, sometimes I notice that when I let off the gas after it kicks in, the car will brake violently and pull to the left or right, almost dangerously.

The car's ABS also occasionally kicks in during normal routine stops. The cruise control sometimes works, but mostly doesnt.

The car is not reporting any codes, on any of the different pins. The tires are all the right size, all have same tredwear, and all the correct pressure. Im really dumbfounded as to what it could be. There is no dummy lights on in the dash. Curently I have disconnected the drivers front ABS sensor so that the car is drivable.

Ive replaced the brake switch and that did nothing. The car has a new engine harness and also a new EA harness.

Im wondering if it could be a bad OVP relay or an ABS sensor? What should my next course of action be? Im surprised the car is not reporting any codes.

Thanks to all who respond...

mbdoc · #2 09-22-2008, 08:07 AM

Check the circumference of ALL 4 tires closely, even 1/4" difference can cause that!

amg280 · #3 09-22-2008, 08:37 AM

Quote:

Originally Posted by M.B.DOC

Check the circumference of ALL 4 tires closely, even 1/4" difference can cause that!

I did. They are all brand new. To add insult to injury, I even took the brand new michelins off my 400E and put them on it, same thing.

Not sure if this means anything, but when it was on the lift, I put it in drive, and the ASR immedietely kicked on and was braking the rear wheels (like it should be). My only concern was that I wasnt on the gas. Shouldnt ASR be inactive until the system recognizes the driver is on the gas. Could the sensor be bad on the gas pedal?

thanks!

Arthur Dalton · #4 09-22-2008, 10:04 AM

Check the WSS ....specially as you are having ABS lamp as coming to a stop.

amg280 · #5 09-22-2008, 10:05 AM

Quote:

Originally Posted by Arthur Dalton

Check the WSS ....specially as you are having ABS lamp as coming to a stop.

How do I check the wheel speed sensor?

Arthur Dalton · #6 09-22-2008, 10:07 AM

You can start with a DMM and spin the wheels..also ohm them for spec.
You can also pull them and see if they are full of crap and metal filings.

There is a good post about them from a few weeks ago..do a Search.

amg280 · #7 09-22-2008, 11:23 AM

Quote:

Originally Posted by Arthur Dalton

You can start with a DMM and spin the wheels..also ohm them for spec.
You can also pull them and see if they are full of crap and metal filings.

There is a good post about them from a few weeks ago..do a Search.

Found the post. Thanks! This car has been sitting for 3 years, so it very well could be a bad sensor due to rust. I will test them wed and report my findings....

Arthur Dalton · #8 09-22-2008, 12:09 PM

If it has sat that long, I would pull the fronts and clean them, and also do the reluctors, specially the valleys..I am sure they will be full of crap too. Then spray some brake cleamer in the sensor hole as you spin the wheel..that should clear them up...

amg280 · #9 09-24-2008, 11:33 PM

Well I took both front wheel sensors apart tonight. I cleaned the valleys in the reluctors, sprayed with brake clean, and also cleaned the sensors themselves. I put the whole rig back together and same thing. There was no pre-mature ABS intervention however.

Im telling you, this thing is weird. The ASR will kick in for no reason. It kicked in so violently tonight, it made the rear wheels screech, all while i was on neither gas, nor brake. Thats dangerous. Especially at 60mph, the speed we were going. If im off the gas, and the ASR still kicks in, is it safe to say the switch at the accel pedal is bad, telling the computer im on the gas? Can some of ASR gurus help me narrow down what I should be looking at? What can I rule out? Still saying no faults in system on all pins (1 blink).

This is really starting to pi$$ me off, since I went through the gamut of ASR issues with my 400E. Is there an easy way to completey shut off the ASR, yet keep the ABS alive?

Arthur, Im still going to try to OHM test them tomorrow. I ran out of time tonight.

amg280 · #10 09-27-2008, 09:19 PM

Ok I ran alot of tests yesterday. I have come to the conclusion that its the front passenger side ABS sensor.

1. I ran ohm tests on all the sensors. All were in range and equal to its side-side counterpart.

2. Tested acceleration sensor @ gas pedal. Works as it should.

3. Had my gf drive the car while I AC volt tested the rear wheels. Both provided an increasing linear output as speed increased.

4. Did the same test with the front left sensor, same thing.

5. Proceeded to test the front right sensor, problem! It would increase right off the start, and then just hit a dead zone, no more rise as speed increased.

Am I safe to say this is the culprit, even though it ohm tested fine?

On the back wheels, there was a slight variation from left to right, but not much. What is the tolerance spec for side to side?

And also, why is it so hard to source a new ABS sensor for this car? Everyone is telling me its a dealer only item. Could I splice a new sensor into the wiring harness? The only difference I can tell from other W124 cars is the connector under the hood.

Thanks for all the help.

amg280 · #11 10-01-2008, 09:04 AM

Well I installed a new wheel sensor on the front pass side. Still does the same thing!!

I checked the output, and it was still barely giving anything (ac volts). It was howerever directly proportional to the wheel speed now, just on a tiny scale, maybe even 1/10 of the drivers side amplitude.

The ABS now kicks on at every stop, and the ASR barely allows the car to accelerate. ITs much worse now.

How should I proceed? The distance from the sensor to the teeth isnt adjustable. I dont want to bend the sensor to try and get it closer to the teeth, am I going to have to replace the hub too? After I got such low readings, I took the hub assembly right off the car and brought it into my basement where I sanded all the rust off with a wire wheel. I also hit up the mounting surface as well to make sure the new sensor was fully seated. The sensor ohm tested fine, btw.

After I put all the freshly polished parts back on the car, it still did the same thing, however, the amplitude went up about 15%, still wayyyy off of the drivers side output (alot higher!!)

My local junkyard has a wrecked 95 320 I can buy the hub off, but I dont want to buy it if it isnt defective. However, that would be the only thing left in this puzzle, right?

Please help...

Arthur Dalton · #12 10-01-2008, 09:44 AM

http://www.picoauto.com/tutorials/diagnosing-abs.html

mbdoc · #13 10-01-2008, 11:46 AM

You need to look at the wheel hub "teeth".

Even a nick can cause that speed sensor issue.

amg280 · #14 10-02-2008, 09:32 AM

The teeth look all uniform, albeit highly corroded. I dont know if they are worn down or not, since i dont have a spare to compare it to. If this issue is caused by an excessive spacing gap, is my only option to get a new hub, and hope the teeth close that gap, or is there something I can "rig" or machine to close the gap.

mbdoc · #15 10-02-2008, 10:11 AM

You could try switching hubs side ro side or even switching one from another car.

??? is the ABS light also coming on?? IF not then the sensor may not be causing the problem.