I just got the yesterday. It is a 1989 560 sel. It had sat for a year before i got it. I drove it home about 160 miles. Running down the road it seemed to run fine. The problem is with idling. It seems to be missing a little. No smoke or any thing does not seem to be flooding out nor does it starve for gas when you take off. I put new plugs in it today and it runs a little better going down the road but gallops at idle. Looking at the cap and wires thay look fine . But how do you tell if there original. there is some valve train noise on the passenger side of the car. any ideas on the missing? the car has a tad over 115,000 miles on it

Many possibilities:Too much slack in the timing chain.
Vacuum leak.Bad Vac. control valve.I would also check the rotor and cap.

If you don't have the service history, I would recommend replacing the timing chain, upper slide rails, plastic oil tube pieces, and chain tensioner.

If you do this, and don't see any obvious wear on the cam lobes or rockers, then you probably have balls studs that are leaking down and not holding the rockers tight against the cam lobes. I would try "part synthetic" oil and a couple of 500 mile oil changes.

The miss at idle could be anything from cap/rotor to a plug wire to an injector to the fuel distributor to a vacuum leak. You need to work your way up the "expense chain." Lots of posts on doing this.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

I changed the oil in it today and it looked like it has not been changed in years. the oil filter was falling apart when we took it out. i checked for vacuum leaks today but i didn't see any or hear any. how do the transmissions normal shift in these cars? It seems like this one shifts real firm for the type of car it is. What controls the shift is it vacum or is it some thing else? What about vales is it common for a burnt valve in these cars. how do you check for chain ware what do you have to take apart? i do not know about the records but the maintenance booklets last serves stamp was at 90,000 miles and that was like 12 years ago. thanks for any help