My Unruly mazda

I have a 1990 Mazda 626 LX 4 cyl. that “bucks” when accelerating from a dead stop. This happens only in cold weather and is worse when going uphill. Someone told me it is the vacuum advance. How can I test this and fix it?

I would check the TPS . sensor. it tells computer to add spark advance . you might have one bad spark wire or plug. or one coil or part of coil if you have two coils.

I should have mentioned that I replaced the spark plugs and wires and distributor cap and button. I’ll check the TPS sensor. Thanks!

Check the plastic air supply. They deteriorate and split at the pleats. Weak motor mounts exaggerate the problem, when under load and moving forward, the engine moves rearward and streaches the pipe causing a leak which subsequently causes air to bypass the MAF. The leak causes the engine to lose power and begin to return to its at rest position but in doing so the leak is stopped and power is restored. This often causes the bucking.