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91 m103 low idle at start, lean duty cycle, adjust airflow affect low idle?

5K views 5 replies 3 participants last post by  johnathan1 
#1 ·
On my 91 300te m103:
Starts quickly, idle low, dies.
Starts again, better, usually does not die.
This am had someone start whilst I slightly pushed down on the airflow plate. No idle problem, started and held.
Will the 3mm tower adjustment affect thestart idle?
This car h as never had the 3mm tower adjustment, plug still in place.
Duty cycle 50% open loop, 78% closed loop (3v/13.9v), 54% at 2500 rpm.

Checked, tested,replaced as needed
OVP
Throttle switch
Idle air control valve
Crank sensor with connection at EZL (got the TN/TD signal interrupted on pin 14 code- cleared and checked with engine running, code does not appear. Think it is a code that appears as koeo testing is done)
O2 sensor
Potentiometer
Non resistor plugs, Dist cap and rotor
Plug wires
Fuel filter
Cleaned fuel injectors, pintles open ok, spray pattern ok.

So will adjusting the airflow sensor screw move the airflow sensor plate to the good engine idle start position?
Input appreciated and wanted.
As good mechanic once told me: Let's see if it works.
 
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#2 ·
78% is too high (or low if your DMM is craftsman), get it down to about 60% and see what your 2500k rpm is then.
My only concern with the above though is if its REALLY still the original anti-tamper plug. If it is, I would lean towards leaving it alone since its actually on the correct factory position and your problem is elsewhere. If it has been tampered with, but a new plug on, who knows.

Was OVP replaced? Start there first regardless of checks. They all go bad and you can end up chasing ghosts so its a wise investment to just replace it with a new Kaeler (KAE) or OE.
 
#5 · (Edited)
No and I know the ovp is good per the test I posted above. Is this test not valid?
Should be accurate.
If I replaced parts in a modulating condensing boiler like that-- too expensive to play with- like a Mercedes!

How to get mix down ?

Watching air flow plate drop and holding it in initial positon after ignition (1 sec), no idle problems.
How to adjust this?
Picture of anti tamper plug
 

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#3 · (Edited)
Don't want to chase ghosts. I thought I had found them all.
Have been trying to find an external solution to this problem without lambda adjustment.
Using a voltage test for lambda so 3.0 avg/13.9 on X11 2/3 2/5 pins
Low v = lean?

When I tested the ovp (red top 2 10a fuses) several times the solenoid was good and the voltage on the pins was exactly the same as input.
I thought this was a good test.
tested several times over 2 days, even put it in the freezer'.

When started several times over the course of the day, there is always a slight "want to die" moment, then picks up rpm and runs. Cold in the morning it is "I will die".

What else can I check for open loop start problems?
EHA- resistance and voltage ok (no mA check yet)
Micro switch resistance open/close fine.

Just feels like there is a test or adjustment I'm missing.
In a carb system, I'd be doing the air/fuel adjustments to tweak it, and, that;s what this feels like= something that needs tweaking.

Gracias
 
#4 · (Edited)
1.The last two mornings, someone else started the cAr.tarted quickly.
Airflow sensor plate dropped on ignition and immediately (1second) began to rise and engine stall.
Had my finger there on the airflow plate to keep it down and idle great. Car started warming (but still in open loop 40c) finger off idle moved around as I very slightly pushed an released plate. After another 1.5 minutes idled ok (not great) on its own.

2. Starts ok the rest of the day usually.
Never has stalled whilst driving.

3. Tested idle air control valve off car with 12v, snaps open and closed.
get 9 v between pin terminals dropping to 6.4 (stopped testing) as engine temp rose slightly at idle, cold. Normal?_

In any time/temp/loop condition, disconnecting IACV drops idle immediately. Plugging back in while still running does no change. Have to turn off and restart for idle to go back to prior rpm.

4 .Tested the ovp many times under varying temp conditions and it passed every time. Does the test method not work?
Posted at end of reply.
Do not have one and thought the test methods were accurate (also tested voltage at sockets).

5. Have tested 4 pin temp sensor, replaced rubber on all vacuum hoses in addition to the above..


Any thoughts from the experience here?

Why do you think this initial start problem, corrected by just not letting the airflow plate rise 1 sec after ignition?
Regards, Tom

OVP TEST
 

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