I HAVE AN Y REG NISSAN ALMERA THAT IS SPLUTTERING AND CHUGGING ESPECIALLY AT 30 MPH IN 3RD GEAR. DOES ANYONE KNOW WHAT THE CAUSE OF THIS MIGHT BE?

Your clutch is going out. Time to replace clutch

Check your belts and pulleys. Belts should not be cracked and pulleys should turn freely with no noise.

I guess my first question would be - are you saying it is slipping in 3rd gear ? If you push the gas pedal to the floor it should downshift into a lower gear.
If it is slipping, or not upshifting into 3rd gear, I'm afraid chances are the transmission is toast.
You can take it to a couple of shops for estimates but they will probably want to pull the pan and take a look inside.

You must get the system scanned for fault codes first. I doubt it is plugs.

Are you sure the trans is in 3rd. Pull the stick into low gear accelerate shift to 2nd about 20 mph shift to 3rd about 35 mph then 4th about 50 mph. This will let me know how to go further with your problem. If you do this proceedure write the results on this Great FixYa Page!

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Replace transmission.

well Im sure theres a ton of miles on it-do u perform reg maint like checkin fluid level-u may need the throttle cable ajusted that hooks to trans-band n clutch could be out of measure too--trans hydra-valve system could be worn--see all these things effect the way the fluid makes the gears move--a pressure test can confirm an aging trans

sounds like the selector box at fault but change the auto oil and filter with some treatment and this should solve youre problem

tranny shop time tranny pump problem