throttle actuator? - Page 2 - PeachParts Mercedes-Benz Forum

EricSilver · #16 04-14-2009, 09:00 PM

I just measured voltage at battery:

. 12V engine off
. 14V engine on.

will see if I can run some longer wires into the passenger compartment in the morning, when the problem occurs. I expect it will happen when I hit the accelerator for the first time, so that is when I will be watching the meter.

EricSilver · #17 04-14-2009, 09:21 PM

Quote:

Originally Posted by M.B.DOC

I use an old radar detector plug connected to my Fluke that has a min/max recording feature.

I plugged my Garmin GPS power cord in the lighter. I put the positive probe from the meter into the center of the business end of the plug, and touched the negative probe to the outer sleeve, getting good engine off/on voltage readings. Will know for sure tomorrow a.m. if there is a spike when the fault is triggered.

EricSilver · #18 04-15-2009, 12:08 PM

Based on my test results, I may have a cause, or simply another correlation.

Recap: Last night when I measured voltage, after a very short drive, its was:

12V – Engine off
14V – Engine on

This morning:
12.25V – Engine off
14.5V engine on

Conditions were perfect: Rainy and cold. After startup, tapped the accelerator to trigger the ASR fault, and it delivered. Voltage held steady at 14V. Shut off, restarted, no change in voltage.

(Note: The relay ping which I previously said was behind me may be an acoustic illusion. Depending on how I tilt my head, it sounds like its also coming from behind the passenger dash, where the OVP lives.)

While driving, voltage held rock-steady at 14V. Pulled over into a nearby shopping center to idle while the car warmed up. Still, voltage held at 14. Headlights were on the entire time. Switching on seat heater and radio barely moved the needle. However, turning on rear window defogger and blower motor dropped voltage to about 13.25. Turning them off returned it to 14V.

After about 8 minutes, coolant was at 82/83 and voltage had dropped to about 13.1V Engine-off was still 12V. Restarted, no ASR fault. Took a 30-mile road trip and voltage held at 13.1, with a possible increase to 13.25 or so on the highway, but I did not take my eyes off the road long enough to verify that. Upon arrival at my destination, voltages were:

12.1V - Engine Off
13.0V – Engine On

When MBDOC mentioned a spike I assumed a momentary one, but it would appear I experienced a spike lasting about 10 minutes, beginning the moment I started the car.

So: Appears I need a new voltage reg, correct?

anziani · #19 04-16-2009, 11:17 AM

Eric,
I have the opposite problem. If my voltage stays in the 13VDC range, I get the so called limp home problem. It appears that if my car starts up and the voltage is 13VDC then I get limp home. If, when it starts up and I get 14+, then I don't get limp home. The minute it hits 14+ volts, it goes away AFTER I restart. I am getting new regulator today. It was my assumption that a good regulator and alternator would always generate 14+ volts. Anyway, I will post my results.
Anziani

EricSilver · #20 04-16-2009, 11:27 AM

Good timing on your post!

Here’s what happened today:

Conditions: Sunny, Dry, and a few degrees warmer

If high voltage/current was the problem, my intent was to outsmart the system by having a large load present at startup. After energizing, I turned on the headlights, fog lights and blower motor for a nice current draw. Started the car, tapped the accelerator, the idle surged, hit the brake, and nothing happened…. For about 15 seconds. Then the idle dropped and the ASR light illuminated. Repeated with same results. This is a far longer than the 2 seconds it would take the fault to occur without the added electrical load.

The end result\was the same as always: Coolant reached 82/83, and ASR fault disappeared.

However, today, the alternator voltage stayed at 14.1-14.2 during and after a 30-mile drive. (Yesterday it rained and my passenger side hood drain clogged, backing water onto the wires in the fender/footwell areas. If one of those was a power line, I conjecture that could account for the voltage loss I experienced yesterday. Today, in dry conditions, alternator current was fine.)

This keeps pointing back to a coolant temp issue. Tomorrow morning, if weather is cool enough, I’ll disconnect the sensor before starting and see what happens.

EricSilver · #21 04-16-2009, 11:30 AM

Quote:

Originally Posted by anziani

It appears that if my car starts up and the voltage is 13VDC then I get limp home. If, when it starts up and I get 14+, then I don't get limp home. The minute it hits 14+ volts, it goes away AFTER I restart.

It would appear my VR is functioning normally. Back to my checklist....

EricSilver · #22 04-17-2009, 11:32 AM

Is there another coolant sensor on this car, aside from the one(s) on the thermostat housing? This is what happened:

Last Weekend: While changing air filter, and cleaning sensors and connectors, had the coolant temp sensor unplugged and decided to start the car. Engine was warm/hot. Electric fans came on and engine fired right up (no ASR issues since engine was warm).

This Morning: Engine cold, unplugged coolant sensor and started car. Cranked but did not turn over. Tried twice. Electric Fans did Not come on. Plugged sensor back in, started car, it turned over normally. Unplugged sensor while running. RPMs dropped from about 1100 to 600. Waited about 15 seconds for ASR to appear, which it did.

Drove about 5 blocks to shopping center parking lot. Coolant temp was about 45-50. Shut down car. Disconnected sensor. Cranked and car restarted, but no electric fans. Waited for ASR to clear. Drove 20 miles. Engine hot. Shut down. Disconnected sensor. Restarted – electric fans came on full blast, and car started normally.

My understanding was that with the coolant sensor disconnected, the electric fans should start the engine should not. So is there another sensor I am not aware of? Or is there some dirt/corrosion in the sensor connector affecting sensor/resistance readings when weather is cold or damp?

jcyuhn · #23 04-17-2009, 12:41 PM

Yes, there are three sensors on the waterpump/thermostat housing - one for the ECU, one for the fan relay, and one for the climate control. I accidently unplugged the ECU temp sensor on my '93. It was difficult to start cold, but ran fine warm. I'm assuming that without any engine temperature data, the ECU didn't deliver any cold enrichment, hence the no/difficult start. It would start if you gave it some throttle.

BTW, I think your voltage regulator looks normal. A few minutes of 14+ to charge the battery following a start, then dropping into the 13 range is completely normal.

- JimY

EricSilver · #24 04-17-2009, 01:10 PM

Quote:

Originally Posted by jcyuhn

Yes, there are three sensors on the waterpump/thermostat housing - one for the ECU, one for the fan relay, and one for the climate control. I accidently unplugged the ECU temp sensor on my '93. It was difficult to start cold, but ran fine warm. I'm assuming that without any engine temperature data, the ECU didn't deliver any cold enrichment, hence the no/difficult start. It would start if you gave it some throttle.

BTW, I think your voltage regulator looks normal. A few minutes of 14+ to charge the battery following a start, then dropping into the 13 range is completely normal.

- JimY

Jim thanks for the cold/warm starting and voltage explanations. But shouldn't the electric fans have come on this morning?

I have a late '95 car with the '96 configuration -- just two coolant sensors, with the ECU and fan merged into one 4-spade unit, and obviously wondering how it is appears contributing to my periodic ASR faults.

The wire harness is in great shape (only about 4 years old) so some phantom component, that requires about 10 minutes to warm up, even in sub-zero weather, is triggering the condition. Since I have replaced a badly deteriorated coolant reservoir cap o-ring, and a failed coolant level sensor in the past months, and their apparent rate of decomposition would seem to correspond to the timeframe in which my ASR problems began, I keep gravitating back to that.

jcyuhn · #25 04-17-2009, 03:08 PM

Dang, they change these cars a lot. Yeah, I would think with the single 4 connector temp sensor that your fans would come on. I don't know what's going on there - don't have time to dig into the wiring diagram today.

I've never owned a 124 with ASR, so don't have much to offer there. It's difficult to imagine how ASR operation might be tied to coolant temperature - I can think of why to two would be related. Do you think it's more likely to be something like a poor or intermittent electical connection in the wiring harness? Perhaps one of the pins has partially backed out of a plug connection?

- JimY

EricSilver · #26 04-17-2009, 04:46 PM

Quote:

Originally Posted by jcyuhn

Yeah, I would think with the single 4 connector temp sensor that your fans would come on. I don't know what's going on there...

It's difficult to imagine how ASR operation might be tied to coolant temperature - I can think of why to two would be related. Do you think it's more likely to be something like a poor or intermittent electical connection in the wiring harness? Perhaps one of the pins has partially backed out of a plug connection?
- JimY

I would also think the fans would come on, regardless of engine temp, when the sensor is unplugged. But this morning, when cold, they did not. When the engine was warm/hot later on, they did. So that's an obvious sensor -- or sensor connector -- anomaly.

I understand that ASR is not directly related to coolant temp, but since idle speed control is related to coolant temp and ASR is related to idle speed, could there be something strange occurring in that triangle?

The wiring harness is relatively new, but I most definitely believe a poor/intermittent connection or signal is the culprit, especially since very high humidity on the first start of the day in the dead of summer will trigger the fault as readily as cold temps in the winter. That screams, "electrical." Something needs time (approx 10 minutes) to warm up and/or dry out, and I am leaning towards warm-up. And coolant does not need to reach operating temp. If I raise the temp to, say, 60, then go shopping for 20 minutes, when I get back the temp may be 50, but the car will start with no ASR fault.

Here is something else to chew on: In the summer, on this car and my previous one, I have observed that when driving down hill, or decelerating, coolant temperature drops. The hotter the engine temp, the more dramatic the drop. I can only conjecture that inertia is moving more coolant forward into the radiator, and/or slowing the escape of that which is already there. The temperature drop must also be occurring in the winter, but is less noticeable on the dash gauge.

On every occasion in winter driving when the ASR fault kicked when I was underway, it occurred only -- repeat only -- on deceleration (not necessarily with braking) and especially when going down hill, i.e., decelerating down an exit ramp; or decelerating down the curved, steeply inclined ramp of a parking garage; or, most notably, on a bitterly cold day on I-95 when decelerating from about 80 to 70 mph (no braking) in 20-degree weather.

My simple-minded theory is that, because of the faulty sensor, possibly related to internal corrosion, the computer is reading a rapidly fluctuating resistance (when the sensor or sensor connector is cold) and doesn't know what to do until the sensor/connector warms up and sends a more constant/stable signal. (During some recent online research, I happened across a experience someone had with a failing, corroded, coolant temp sender linked to their dashboard gauge. He/she described how the gauge would peg very hot, then drop to zero, repeatedly. I don't know how a an engine computer would react to something like that, but I suspect it would not be pleased.)

So, yes, I definitely believe it is a fault in a wire harness connector, or a sensor/component linked to said connector, and I have focused on the one that is 1.) most directly exposed to weather; 2.) which is directly involved in the coolant temperature behavior; and 3.) Which now appears to be exhibiting anomalous behavior (fans not running when disconnected if engine is cold).

Sorry for the small novel.

Douge · #27 04-17-2009, 05:02 PM

I had the same prob with the same error code and tech diagnosed a faulty actuator. I replaced it with a used unit and it did in fact correct the problem.

EricSilver · #28 04-17-2009, 06:00 PM

Quote:

Originally Posted by Douge

I had the same prob with the same error code and tech diagnosed a faulty actuator. I replaced it with a used unit and it did in fact correct the problem.

You are definitely in the lucky minority for whom that worked.

anziani · #29 04-29-2009, 11:29 AM

Well, we pulled the alternator and took it to an electrical shop. They found that there was some solder on the "ground" side of the voltage regulator and some possible arcing. Ah Ha, I thought. This is it! Replaced the regulator, hooked up my VOM and drove the car. Voltage stayed at about 13.8 VDC. The car ran perfectly for 3 days and on the 4th, the strange problem returned. (loss of power after a block on a cold engine, no ASR light, cured by restarting the car, never to happen again during the rest of the day.)

In reading the posts on faulty OVP relays, it doesn't seem to correspond to those problems but I will have to try another relay to see if this is the culprit.
Anziani

'93 300CE 172K
'95 E420 117K

EricSilver · #30 04-29-2009, 05:58 PM

I was wondering how that turned out. Now, welcome back to the confusion.

Quote:

Originally Posted by anziani

... a cold engine

This is the common denominator.