I have a fully-restored '88 420SEL which hasn't been driven in about 7 months and I am starting to use it again. The battery has been recharged and I have run two tanks of gas through with Techron at the suggestion of my mechanic, including a DC to Philadelphia highway drive.

It cranks immediately when cold (with an initial idle at 800 RPM or so -- goes up to 1,000 when first starting, then settles down to 800) and runs normally except that:

(a) the in-gear idle is about 800 RPM (in drive or reverse),

(b) when put in park or neutral, the idle pegs at 1500 RPM and stays there (it goes back to 800 when put in gear),

(c) the oil pressure gauge also pegs at "3" and stays there during driving, whether going 80 MPH or idling at a stop light (my recollection is that it previously was always very sensitive and would normally vary appropriately between 1 and 3 according to RPM and accelerator pressure, going down when stopped at idle and increasing when running), and

(d) when you turn off the engine (parking to run an errand, etc.) and recrank it, you have to give it gas to get it recranked and then run it for a minute or so at a higher idle before driving to avoid a bit of stumbling when first starting out again.

Interestingly, this (d) phenomenon does not occur from a cold start -- you do not need to push the accelerator and give it gas to do a cold crank.

Would appreciate any insights -- fuel delivery issue (keep using the Techron)? Idle control valve/idle control unit? OVP relay?

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'98 C43 AMG
'88 420SEL
'93 190E Limited Edition (including factory Sportline package)