There could be a hundred things wrong with that car. like someone else who recently posted, you are using the shotgun approach, replacing everything. That is going to get very expensive, especially when you dont know what you are actually replacing (ie- 'squared boxes')!

Better try a different tack or your $400 car is going to get very expensive.

Where are you? what year is your car?

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'90 300SE 298k
-300K and it gets put into retirement.
'80 300D 255k Purchased new by family in 1980.

Had a:
1973 220 (gas)
1980 300SD
1992 400E