On the misfire: Check the ignition points and especially the condensor. Mine was bad on my 74 SLC and caused arcing in the points. Replacing it cured the problem.
I own a 450SL (1974) this car is in excellent condition, run great, but drivers seat is worn out. This car has blue interior, I am looking to purchase used seats preferably in good to excellent condition. Any suggestion where to purchase. please send comments at: R3goldhill@yahoo.com.
On other note on the misfiring: My 450 SLC has the old style distributor cap, and the previous owner apparently had it just slightly misaligned (the hold-down screws do not have a nice positive engangement the way the newer clip-on caps do.) Re-seating it got rid of the remaining misfiring on my car! Replacing the ignition condenser was also crucial. (You may have to search a bit online to find the part.)
A few other tips:
--My car had a high idle when I bought it (about 1300 rpm). Replacing a dried out hose to the manifold pressure sensor helped a lot. I then simply adjusted the idle speed screw.
--Stumbles during warm-up for a few minutes, but then runs fine: I replaced the engine temperature sensor and it fixed the problem.
Questions for others:
--LIkely cause of erratic gauges?
--If you've had a fuel pump fail, what were the early warning signs?
Update on my 1974 450slc from previous posting:
1) Began to be tough to start when cold, but started fine when warmed up and otherwise ran fine.
--Solution: Corroded contacts on thermo-time switch for cold start valve. (Be careful removing the connector, as it has a plastic tang that must be nudged before the thing pops off.)
2) Had been suffering from random, but continual popping and spitting (almost like a misfire). Only occurred when warmed up.
--Solution: Finally cured it by carefully adjusting ignition point gap and setting idle speed to specifications. (It's always the simple things!)
I got a 1974 450SLC from my grandpa. It runs pretty well, but is idling very fast, and the gas peddle is sticking. I can't find out how to turn on the windshield wiper fluid. I have checked all the knobs, but maybe it isn't working. Can anyone let me know which knob it is.
I have a 1975 450sl. The window washer switch is located in the footwell for the left foot.
Original poster here.
I have now had the car for almost 5 years. Since the initial servicing I did after purchase, including the 120K mile service, the car has had only 2 new problems.
1st problem was the battery failed during winter storage - it was old. And, yes, I had the battery on a trickle charger all winter. New battery and it quickly started.
2nd problem was not the fault of the car. I was taking my daughter for a short cruise thru the hills here in Jo Daviess County, and about a mile out of town, as I powered thru a curve, Bambi came 'out of nowhere' and jumped in front of the car. Fortunately he flew forward and slid off the road. Because of the cars age, repair time is longer, about 6 weeks.
I have a 74 Mecerdes 450SL. I got it for $800. All it needs is some interior work and I will paint it. The motor runs perfectly since the former owner put a little over 3k into it and it shows. I can't wait until I finish installing everything which cost me about 1k. A very powerful car for the age.
Haven't had my 74 very long. It has 90,000 miles.
I have just had a tune up done, but it 'lunges' every once in awhile. The mechanic looked for a vacuum leak, but hasn't found one. We know the air conditioner compressor is bad, but didn't think it would cause issue if it was off.
Update on "Bambi Strike".
Car took 1 week less than 3 months to repair. Car required new hood, left fender, left headlight assy, radiator, condenser, fan shroud. Factory hood of these cars is aluminum. Insurance called for used hood, Shop ordered 2 (they were steel) and could not get them to fit. Insurance allowed a new hood (aluminum) - no more problems.
Shop converted AC to R134 (conversion used to require replacing everything and cost $1000's. Now conversion only requires new fittings, about $100). AC now works.
Car looks fantastic (actually better than before the accident).
Total cost of repair was $8500. My cost was $0. Thank goodness for classic car insurance.