94 explorer speedometer and more

my speedometer at times jumps all over the place usaully starts at about 40mph is there anyway to check for codes on a 94 explorer. any suggestions would be appreciated. my engine also pings when i hit 3 rpms. coolant leak to i think it leaks into oil when the car is off it stinks like coolant don't see and visible leak from radiator and after it leaks for a while my check oil light comes on about a 1000 miles after every oil change. thanks for looking. when i also turn in 4x4 it's like i'm going up a uneven hill i sway from side to side these are my problems i bought this explorer for 500$. any help would be great i'm going to clean the maf sensor to see if it help the pinging :banghead:it has 124k miles on it

I had the same thing with my 94 on the pinging issue. I cleaned the sensor but it did nothing to improve it. I replaced it with one I purchased @ autozone for $99.00 and solved the pinging and power issue but know my check engine light is on.