Cold Start Problems Revisited (M103) 1990 300SEL

[Qrash]

Cold Start Problems Revisited (M103) 1990 300SEL:

I had posted a similar thread recently which morphed into unrelated discussions. As reported, my search attempts did not reveal anything quite like the symptoms I am experiencing. The vehicle has 175,000 miles. I replaced a leaking EHA valve at about 145,000 miles plus new ignition wires, rotor and cap at 160,000. Standard copper-tip spark plugs new.

When the vehicle has set unused (and cooled) for four or more hours, it takes several attempts to start the vehicle. The problem has worsened over the past month and is exacerbated on cold mornings (now about 40 deg F). I have tried one of the recommendations (turn ignition on for about five seconds before starting). No change. I replaced the Oxygen Sensor ... no change (but the car does seem to run a little smoother at operating temperature).

Symptoms:
1. First start attempt ... motor kicks over, runs about two seconds and dies.
2. Second start attempt ... same.
3. Third start attempt ... same. For the first three attempts, if I attempt to apply throttle it also dies.
4. Fourth (or sometimes fifth) start attempt ... engine starts and runs as long as sufficient throttle applied and let it warm while holding at about 1500-2000 rpm.
5. If I let the engine warm at 2000 rpm for about 2 - 3 minutes, everything is fine and the car runs and idles perfectly thereafter.
6. If I do not let the engine warm for 2 - 3 minutes and release the throttle, it will buck at about 500rpm ... sometimes dies and sometimes will warm and smooth out to regular idle at 700-750 rpm.

Tests / diagnoses / recommendations? ... Thanks much, Qrash

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[Gilly]

Check fuse in OVP
Possibly OVP is bad
Possibly worn valve stem seals-pull plugs and inspect for deposits.

Gilly