1988 190E 2.3 stalling

[professor]

It occasionally stalls when I come to a complete stop. After replacing the stuff that I listed below now it has a hard time starting where it sputters at low idle then dies unless I keep pressing the accelerator and catch it on time.
Replaced parts:
O2 sensor
Fuel pump
fuel filter
Fuel pump relay
OVP
ICV
ICV hoses (lower and upper)
Fuel pressure regulator
Coolant sensor
air filter
spark plugs
ignition wires
Distributor + cap (ignition)
Complete new exhaust from header down including new cat converter.

Action taken:
Adjusted ignition timing by setting the front balancer where the T mark is exactly on the pin located on the block and the distributor centered on the notch. The strobe light indicated no drift with zero degrees set on the gun while the car is at idle. Beyond that I am clueless if I need to make other adjustments and how.
Tested fuel pressure at the distributor and then tested the fuel pressure differential between the upper and lower chamber (see results below) then I tested the Lambda duty cycle at Pin 3 while at idle (see results below).


Test results:
Fuel pressure 5.5
Fuel differential .4
Duty cycle 50%

Please, reply only if you know what you're talking about Pictures will help as I have severe ADD

[pawoSD]

Crank position sensor is a common issue for a slowing to a stop/idle stall. If it even briefly doesn't get a good signal from it then it shuts down the fuel system. Happened on our 300E until I replaced it.

[professor]

I think I tested for that one but I don't recall the details other that I didn't see anything out off specs. I will check my notes.

[professor]

I checked out that part at ******** (description and price)
but I have a feeling that it's not the right one.

Picture from link
[IMG]http://www.***************/secure/PartImages/0021531328.jpg[/IMG]

Can you confirm?

[pawoSD]

Originally Posted by professor

I checked out that part at ******** (description and price)
but I have a feeling that it's not the right one.

Picture from link
[IMG]http://www.***************/secure/PartImages/0021531328.jpg[/IMG]

Can you confirm?

Thats not it, thats the "tachometer pickup". The crank position sensor is at the back of the engine. It costs about 2x as much and looks like this:



Mine still tested within spec too.....but the new one "Tested better" within spec.....and I haven't had it stall since I replaced it. (months ago)

[professor]

That's what I thought, thanks!

[professor]

What are the probabilities for one of those to go bad? It has no moving part and I believe it uses a Hall effect to signal to the EZL, is that correct?

[pawoSD]

Originally Posted by professor

What are the probabilities for one of those to go bad? It has no moving part and I believe it uses a Hall effect to signal to the EZL, is that correct?

Not sure on that, but it seems they do go bad when they are older. Not so much from "wear" as the degradation of the wire and connections. After 20 years they seem to just fall apart.

[professor]

Ok, here is an update: I figured out why the car was not starting properly and that was the OVP being loose from the its harness. The car started right up after I took care of that issue but that didn't solve the stalling issue at a stop.
I went ahead this morning and swapped in a crank position sensor that I pulled from another car just to see if that would make a difference; nope! I am still having the same issue where the car stalls at a stop.
The stalling comes in different flavors where sometimes the rpm surges a bit, sometimes it simply drops to 500 or the rpm start fluctuating up and down with the oil pressure doing the same; all these observations are right before the car stalls, it all depends what the car feels like throwing at me.
I did hear some sort of relay clicking in one of my stalling sagas. It sounded like it was on my left side near the speaker. As soon as I heard it click the car went dead.

[dpkreuze]

Is the duty cycle fixed at 50%? Can you rig the car so as to read the duty on the road? No intake leaks? Just thinkin'.

[professor]

Originally Posted by dpkreuze

Is the duty cycle fixed at 50%? Can you rig the car so as to read the duty on the road? No intake leaks? Just thinkin'.

My air/fuel mixture tower is still intact with the sealed ball and I intended on keeping it that way as much as possible. The 50% duty cycle I got was at idle; I forgot to measure at other rpms But remember my O2 is brand new.
I can rig the car where I can read the current to the EHA and the voltage from pin 3 on the test pod but the car does not have any issues while moving (as far as I can tell).
The current on the EHA when the car is warm and idling fluctuates between +1mA and -1mA. Does that help?

As to intake leaks, believe me, I went through this think in every way. The only leak I have is at the control valve for the heater unit inside the dash. That one is so small that I wouldn't think it would have such a dramatic effect as to stall the car.

[dpkreuze]

The fixed 50% reading indicates no o2 sensor function. I would test the o2 sensor with a volt meter. I would also lose the ball in that mixture tower. The on/off ratio is a starting point for all other diagnosis from what my feeble mind recollects. A fluctuating 50% may be ok tho.

[professor]

Ok, it wasn't a steady 50% so yes you're right, if it was steady then the O2 could be fubar but that's not the case here.

[Max47]

Hi,

Look like a cold solder in the electronic component behind the battery.

Your duty-cycle is perfect, your EHA too at -1 to +1 mA

Take a hammer and gently thumble all the electronic component behind the battery at idle, engine at 80C°. You may hit the one who make the car stall.

Max

PS. Don't use a 4 pounds hammer

[pawoSD]

I would be betting on the air flow potentiometer being worn out.