dolucasi

You're welcome rufrob. 3rd shot was the worst form me too. It took me 3 days to get back to normal. Yet better than being incubated in a hospital....

Let me know how things measure with the AFM potentiometer after you are back to normal.

When you are done with all the AFM pot issue, we need to address your economy gauge as well. On a manual transmission that gauge needs to be pegged all the way to the left at anything over 700rpm with AC turned off and no heavy load on the Alternator (like aux fans running). If you have a working calibrated gauge that is 17inch-mercury of vacuum. I calibrated mine. Mine is pegged, and has always been accept in one occasion that I fixed. Let us not deal with that now, as we have bigger fish to fry and again, let's fix one problem at a time.

- Cheers!

rufrob

Heart was willing but body was weak.

1 meeting yesterday was like a gremlin hit by water. Tuned into 4 meetings. Thankfully much got sorted out. 12-7 I couldn't eat. I was done by the time I got home. Had a beer and zoned out. I should get to it this evening time permitting.

rufrob

I've been crazy busy with work and project which has been on hold for parts. I've been dealing with rust bolts and fasteners, hard to access places, seized hydraulics and water pump. And of course hard to find replacement parts.

rufrob

I'll get back to the 16v when the F3 race car is running.
The pedal box and front hydraulics are done next find or rebuilt the water pump. I already have the timing belt and tensioner.
Then the fuel system and properly clutch.

dolucasi

Impressive. Are you repairing for someone or are you racing the F-3?

rufrob

Repairing it for someone.
Told you here they give me the jobs no one else wants.

rufrob

I pulled the AFM and I noticed strange marks on it. I looked used since it's dirtier than surrounding components.
And one of the arms which touch the AFM was bent.
I got the following measurements

Ignition on
6-2=12.08
3-2=3.67
Cold idle
6-2=13.76
3-2= 8.28
Then it stalled an wouldn't restart.
It started doing the same thing. The sensor plate would go down at start then pop up and the engine stalls. If I adjust the throttle too tight to keep it open it would idle but it wouldn't rev and would stall.

dolucasi

I wish you had just followed the instructions in post #49 first before removing it. Now that you have put it back together. Can you take those measurements and report them?
#49. With the bent contactors of the AFM plate lever replacing the AFM pot would be futile.

Mercedes only sells the entire AFM assembly (with the AFM pot on it) for good reason. It assures the contactors are not in bad shape.
Unfortunately that assembly costs $500. AFM pot is $200.

But Before jumping to conclusions first take the measurements asked in #49 so we know what is going on from a far.

- Cheers!

rufrob

Yeah sorry I muffed that. I blame terrible hay fever, meds, and inpatients

190Efan

As a fellow allergy sufferer, I'm totally sympathetic on that issue. It also sounds to me like previous owners of your car have used lots of questionable, mystery, aftermarket parts and that could also be part of the problem. This is why my engineer father always taught me to use OEM parts only. OEM parts were specifically designed to work with your car and they are more durable and they last longer, saving you money in the long run. I think my money is still on the EHA as your problem given my recent hard starting experience with my own W201. However, it's really important to go through a step by step check list to test every possible scenario in order to find the true culprit part. Dolucassi has provided a really good road map for doing just that so I would urge you to follow that road map and then let us know what your findings are. That will give us the best chance to help you diagnose the problem.

rufrob

Thanks for the message.
The battery ran down from cranking. I charged it and will go through the checklist again.

190Efan

This is pretty obvious but make sure you don't burn out your starter with all of the cranking.

rufrob

Finally got to check the resistance between 1-2 for the AFM Pot. 1-3.56 at WOT
Resistance moves gradually.

rufrob

IGN off
6-2=12.3
3-2=0
IGN on
6-2=12.2
3-2=3.7
I have to keep my finger on the sensor plate to get it to idle

dolucasi

Thank you. The 3.56 value is a little lower than spec at WOT but that is not your problem.

(1) And are there any discontinuities in the readings as you sweep?
(2) Please also measure resistance from pin 3 to pin 1 on the AFM pot. And during the sweep that should not change at all.

dolucasi

Thank you. The 3.56 value is a little lower than spec at WOT but that is not your problem.

(1) And are there any discontinuities in the readings as you sweep?
(2) Please also measure resistance from pin 3 to pin 1 on the AFM pot. And during the sweep that should not change at all.

rufrob

1-3=1.84. No change when sweeping

rufrob

Warmed up engine running
3-2=8.20v
6-2=13.69v
Hard to rev past 2000rpm as it backfires

rufrob

I richened it up and now it rev freely. Next wait and check the cold start.

dolucasi

All your values are less then half of mine. Does not seem right
You are measuring these with AFM pot unplugged right?
Are something is wrong with your meter.
I was expecting an open or a short but that is not the case.
It is possible there is something wrong with your wiring to the ECU or the ECU itself

dolucasi

ECU is still telling you the AFM pot is not working and it will not adjust fuel mixture properly in this state

dolucasi

Futile. If your ECU is not working good luck adjusting that screw.
You need to first diagnose and fix the AFM pot issue.
Unplug the ECU and repeat those measurements (between pins 1-2-3 of the AFM pot) on the ECU side to vindicate the wiring.
Make sure your meter is not uncalibrated somehow as well by measuring a known resistance (in the car our elsewhere)

Like I said previously your resistances are half of what they should be. Never heard of that before unless something went wrong with your measurements or the meter is busted.

rufrob

Sorry I made a mistake. I took the afm pot reading from the harness toward the firewall not at the meter itself
At the afm pot 1-3=1839 some change when swiping but at wot the same.
1-2=1
Gradual increase while swiping then 0 from halfway

dolucasi

Your results suggest you are taking the measurements with the harness plugged in. Unplug it, and re-take the measurements carefully and recording results in detail.
1-3=1839 ohms is not the right value.
Gradual increase for 1-2 is also not correct as it should go form ~1.5K ohm to almost 10.0K ohms during the sweep.

Unless you can converge on what is going on with the AFM pot you will not get very far in fixing your issues.

rufrob

1-3=1.45
Wot=4.40
1-2=1.84
I realize for some reason 2&3 outputs on the afm pot were swapped.
Terminal x
2-6=12.28v
2-3=3.72

Idle
2-6=13.72
2-3=2.83