ASR light on when cold - PeachParts Mercedes-Benz Forum

vidkid1957 · #1 10-14-2003, 08:15 PM

I have a 92 500SL and the ASR light comes on and goes into limp mode 3-4 times in the first 15 minutes of driving. I can get the light to go out by restarting the car. Once the car is warm the ASR doesn't come on. I have had the whhel sensors checked/replaced and the neutral safety switch replaced. Any suggestions?

speace · #2 10-21-2003, 09:56 PM

I'm having fits with the ASR light on my 92 500SL as well. Mine happens when I coast for a while and usually AFTER it's been driven for a while. This morning it freaked me out and did it 2 miles from the house. It's never done it before getting fully warmed up before... I also have an intermittent skip at idle and a hesitation (single-cylinder miss) when I accellerate off of idle.

I am hoping my 3 problems are related.

I will be watching this post for ideas as well.

Gilly · #3 10-21-2003, 10:08 PM

You both need to get the fault codes read out in the ASR/EA system. In both cases it's quite likely that they need throttle motors, BUT you need to find out what fault codes are stored.

Gilly

speace · #4 10-22-2003, 12:41 AM

Thanks Gilly,

In my case my shop says that there are no codes stored. That when I reset the light by restarting the car it erases all of the codes. I did get it to them yesterday with the light still on but I did not hear them say they found a code but they want me to leave the car a few days while they run some tests on some things. I think they said the throttle actuator or something.

That's probably it, now would this also cause an intermittent skip at idle and a miss during soft accelleration? Meaning as I first touch the throttle from idle it skips for about 3 seconds before all cylinders start hitting properly.

Gilly · #5 10-22-2003, 06:26 AM

It could. Throttle motor and throttle actuator are the same thing. They have other names for it too, depending on what literature you're referring to.

It electrically controls the throttle plate (throttle-by-wire, in other words, MB had this over 10 years ago!). If there is a internal problem, it could slam shut under certain circumstances and give you a hesitation or skip. I suppose under certain circumstances, like the throttle plate angle not matching what the quantity of fuel is that's being injected, that it could cause at least what would FEEL like a miss. Remember this is just allowing air into the engine, it's NOT a carb, the fuel injection is still doing it's own thing. The fuel being sprayed in and the throttle plate angle have to correlate.

Gilly

speace · #6 10-22-2003, 07:33 AM

I am very handy at DIY. Is the throttle actuator anything tricky to replace? Does it need any high tech adjustments?

Approximately how much would one expect to pay for this part?

sorry vidkid1957 I didn't mean to take over your post. This COULD turn out to be your problem as well.

Gilly · #7 10-22-2003, 08:29 PM

It's a little tricky to replace, not too bad. You first remove the air cleaner, then the mass airflow sensor (on most of the older ones the mass air flow sensor is mounted right over the throttle motor), then under the MAF sensor, there is a rubber tube which is held onto the top of the throttle motor with another band clamp. That tube is removed, then you'll see the throttle motor is held on with 4 allen head bolts. Remove that, plus the linkage for the limp home, and the return spring, and also that breather hose that leads to the rear of the right valve cover. Plan on replacing that breather hose. If you order one, add one or two base gaskets, as you may mess up the gasket, so have a spare or two. Price on the thing I think is generally around $500, give or take a couple hundred. The EA control unit has to "learn" the throttle stop (closed throttle position) setting. You may need the shop computer to do this, some of them you can leave the key on a few minutes and it'll learn it all itself, while other models seem to need to be "prompted" to learn this with the computer. It won't idle evenly at all until the closed throttle position is "learned"

Gilly

PS once the throttle motor is unbolted, it's a bit of a puzzle to get the throttle motor out of the hell hole in which it lives, kind of have to tilt it upwards in front, then twist it before it'll pop out of there. It's kind of a tight fit too, which is why you typically will want to replace that breather hose. You'll want to clamp that breather on there first to reinstall the throttle motor, and it's frustrating in the extreme to have a tough old rubber breather hose on there, you need a new flexible one to save your sanity.

speace · #8 10-22-2003, 10:45 PM

It does sound a little tricky but it can't be any harder than putting a roller cam in my 65 mustang... LOL

I priced a part today. Woa, what a surprise. I'd better be really sure that it is bad before I make that investment.

I will let you know if I change it and will post the final outcome.

Gilly · #9 10-22-2003, 10:48 PM

How much? was I close?

Gilly

speace · #10 10-22-2003, 11:01 PM

They called it the "Throttle Housing" and wanted 530.00 for the part. I don't know what my shop will want if I let them go for it. I can do it if I have time and round up the hose and gaskets like you suggested. Tips like that make the difference in success or failure because I do my work on the weekend when I can't run to the parts store and get that little gasket or clip and I don't want to risk having to leave the car down for a few days until I can round up the parts to do it right...

Now the Mustang? I can leave it apart for a while, but I can buy almost ANY part for it 7 days a week. There is a parts house nearby that has every bolt, bracket, screw, clip and wire for it that I can think of. You can just about build one of those from replacement parts these days.

The radiator in my SL was one of the easiest I've ever changed yet the one on my 400E was about the hardest. Go figure!
Getting it to clear the fan clutch was a nightmare...

LeaUK · #11 10-26-2003, 05:00 AM

I notice that several people also blame the wiring harness. Where/which harness is this exactly, as I would like to inspect mine?

Gilly - are these codes accessible from the 9pin diagnostic connector (mines a euro manufactured in '92) or is there a separate ASR diagnostic port?

Thanks
Lea

Gilly · #12 10-26-2003, 05:23 AM

In either case (euro or US spec) I am unsure if the ASR/EA is accesible through the 9 pin, I would tend to think it is accessible there. The one MB uses is a 38 pin, located (on a left hand drive car) on the right side under the hood, under a black plastic cover which lifts up by hand (just in front of the firewall)

Gilly

LeaUK · #13 10-26-2003, 08:36 AM

Gilly

Are you saying there are two diagnostic connectors, or that you are just familiar with the 38pin? I think I know where the 38pin connector should be. There is indeed a removable panel where you describe, but unfortunately mine only houses what looks like an hydraulic reservoir

My 9pin is around half way down under the bonnet, beneath a plastic cover held in by three large self tappers. I have looked high and low for the 38pin, but on my '92 I cannot find it. My local dealer clarifies that MB updated the 9pin to the 38way at a latter date.

Has anyone got the fault code list for and connection details for a '92 by any chance?

Much appreciated
Lea

Gilly · #14 10-26-2003, 07:02 PM

On a US spec car, the 38 pin is most commonly used at the dealership. I believe the 9 pin is harder to locate (inside the car somewhere under the dash). The 38 pin is pretty big. I'd look on the other side possibly (on the left side) if you have a right hand drive MB. May be a palstic cap on top of the connector, usually a lanyard hold it to keep it from being misplaced.

Gilly

LeaUK · #15 10-27-2003, 02:27 AM

The 9 pin is most definitely under the bonnet as I have personally found it and it does have a plastic cap and lanyard.

Well, as I mentioned, the dealer said that MB updated the 9 pin to a 38 pin sometime after '92 therefore I can only surmise that I haven't one

One last point Gilly - do you know which harness people are referring to (and where it is) when they speak of harness failure/ASR problems.

Thanks for your help.

Lea