I drive a 1991 Proton Saga that has been giving me this problem lately.
It jerks intermittently when going up slopes, even though it is in the appropriate gear.
What could be the problem and what should the mechanic do to fix it?
- Mah CL
Reply: usually when one has intermittent jerking or misfiring, it is likely to be an ignition problem and is most probably one of the spark plugs misfiring under load.
The reason or this is that one is climbing under load, the fuel system creates a richer air-fuel mixture (meaning there is more fuel in the mixture) and this requires a stronger spark to fire.
If the spark plug is old or the gap is too large, the spark may not fire across the gap and this will result in jerking.
The other source could be a clogged carburettor jet (for carburetted engines).