I recently purchased a 93 300e 3.2 (built in late 92) with 120K miles. There are few maintance issues that I need some input.

I read a lot of posting but still unsure and confused.

Belt tensioner - I replaced the belt. First I cannot find a 19MM bolt. Instead I have 10MM hex nut on the tensioner itself. It is not left hand thread. I losen it and the marker did not turn. Based on all the comments I read the tension needs replacement. Since I did not have a new tensioner, I just tighten the 13mm adjustment nut and tensioner nut. the belt feels tight.
Question - If I can tighten the belt as described, do I need a new tensioner? Why? Will the tensioner apply more presure to the belt after the adjustment is tighten?

Idle -
I think I have a vacuum leak. Please advise me of your thoughts.

Cold start - Start right away. Idle is smooth fluctuate between 1000rpm to 1500 rpm. Sometime idle smooth at around 1000rpm.

Warm engine - symptom is not uniform.
Sometime is very smooth (50 % of time).
Somethime is little rough (30%).....I see the oil presure gauge needle goes up and down. Car sometimes want to surge forward.
Sometime (30%) seems misfiring - idle at 600 rpm.
Acceleration and highway driving - smooth
I have installed new cooper core plugs. While doing it, I see small amount of oil inside the spark plug chamber. I have not replaced the connectors.

Your inputs are appreciated.

Earl

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Earl
1993 300E 3.2
2002 C240
2007 BMW Z4 Coupe
1976 BMW 2002
1992 BMW 318i