1996 E300D Smoking at precise Temp - Page 2 - PeachParts Mercedes-Benz Forum

jfulford · #16 02-05-2014, 07:57 PM

As per GregMN recommendation, I idled the card from dead cold(15 degrees for 16 hours) up, watching my obdii readout on exact temperature. Car was in gear, idle was 625-660. After 20 minutes or so, it was past the normal point of smoke(155F or so) and up to 175, which it held for quite a while. I finally gave up. It DID Not smoke!

Where does this leave me? Only driving up to temp? Still not meaning anything.

Jeff

GregMN · #17 02-05-2014, 08:10 PM

That means that it is not your idle circuit.

Next try to isolate which temp. sensor is on the circuit that causes the problem. Unplug one and go for a warm-up drive from cold. Once you find which sensor, you can trace the signal to the device that is causing the problem.

The signal from your drive-by-wire throttle control is sending a WOT signal to the fuel delivery valve as the engine temp crosses a specific temp. I suspect that if you don't let it know what the engine temp is, it will not send a WOT signal.

jfulford · #18 02-06-2014, 10:24 AM

Update and confusion:

Temperature last night: -2F. Block heater on. This morning at 8AM: Car started quickly(glow plugs cycled quickly letting me know block heater is working). ODBII reader hooked up.

For the first time, I got smoke and injector nailing. In fact, I had 4 episodes of this: start for 5" or so, clear up, 10 seconds later start again, etc.

This happened at 156.8F and the last episode was at 162.6F.

I was doing about 55mph and the rpms were going up to around 22-2350 when it started.

I don't think this rules out(but supports) the Greg's WOT theory. I will start removing temp sensor cables and see if that does anything, as per Greg. I'm tempted to replace ALL sensors I can find in the vehicle!

One other note: This was the coldest morning I've ever driven the Merc; usually I would be driving the Ram because of the snow.

jeff

GregMN · #19 02-06-2014, 01:15 PM

I don't think that the temp. sensor is the problem. I think that the problem is caused by a throttle control device when it senses the coolant is at a specific temp. By unplugging the temp sensor, the device will never know when that temp is reached and will not do what it has been doing.

That is just my thoughts on why to unplug the sensor. If all of that is confirmed, then you can have a talk with the dealer's parts manager and/or service manager to track down the device that might be defective.

Jeremy5848 · #20 02-06-2014, 10:31 PM

Since you have the EGR valve temporarily defeated while you sort out the problem, you can also remove the throttle valve that's just ahead of the EGR valve in the airstream. I rather doubt it's related to your smoking problem but it will help insure that the engine is always getting the maximum available aid.

Jeremy

jfulford · #21 02-07-2014, 01:35 PM

Jeremy5848,
I removed the "flap" in the pipe next to the EGR valve. I kept getting "throttle position" Codes. They started after I removed the flap--the EGR had been bypassed by a month by then.
Just more info(and I think this is because of the outside temperature, 12F), I had 2 more "episodes" on the way home from work yesterday. These events have NEVER happened at the end of the day when the car had been used during the day.
jeff

GregMN · #22 02-07-2014, 03:50 PM

So, your fuel delivery valve is either:
getting a bad signal from the throttle position unit
or
reacting incorrectly to the signal that it is getting

Attached is a diagram of how the control valve functions.

Somewhere I saw a labeling of the 4 pins of the electrical plug for the valve. I cannot find it now.

jfulford · #23 02-10-2014, 11:44 AM

GregMN,
Could I "shotgun" this and replace the fuel delivery valve and have a 50% or better chance of fixing this?

jeff

Quote:

Originally Posted by GregMN

So, you fuel delivery valve is either:
getting a bad signal from the throttle position unit
or
reacting incorrectly to the signal that it is getting

Attached is a diagram of how the control valve functions.

Somewhere I saw a labeling of the 4 pins of the electrical plug for the valve. I cannot find it now.

jfulford · #24 02-15-2014, 06:52 PM

Been away for a bit. Now working on more pressing needs: Radio out(dead radio) and brake squeak(looks like dust). Will try temp sender pull after I get back from vacation.
Jeff

Quote:

Originally Posted by jfulford

GregMN,
Could I "shotgun" this and replace the fuel delivery valve and have a 50% or better chance of fixing this?

jeff

GregMN · #25 02-15-2014, 07:42 PM

I don't think that it is the fuel delivery valve. I do not think that it gets a temp. signal directly (can anyone confirm that ?). I think that something else further up the line is reacting to the temp signal and then sending an errant signal to the throttle valve.

jfulford · #26 02-16-2014, 09:07 PM

You're probably right. I'm just sort of frustrated. I hate throwing money at it. Since I bought the last October, I have had a series of summer days to verify the temps, but I would bet it's a temp thing. I will start what you recommended when I'm back in town: pulling the temp sensor and trying it cold.
Just maintenance this week: brakes and radio(power pulled out--noob mistake). Highest temp outside was high 30s.

jeff

Quote:

Originally Posted by GregMN

I don't think that it is the fuel delivery valve. I do not think that it gets a temp. signal directly (can anyone confirm that ?). I think that something else further up the line is reacting to the temp signal and then sending an errant signal to the throttle valve.