Hello all, I had a similar problem recently (last week)
Model: Wira Auto 1.5 GLi 2002
Mileage: ~ 130,000 km
Symptom: Jerking at low RPM (car shuddering and feeling the loss of power at low speed). Once gets to gear 3 close to 70 km/h then the jerking sensation is gone.
Checked with workshop mechanic (not Proton service center), suspected 3 things
1. spark plugs
2. spark plugs cable
3. Ignition coil
Changed spark plugs since already full of carbon deposits, but this is not the cause. The mechanic used a new set of spark plug cables but symptom remained, and concluded one piston is not firing and it's due to ignition coil. But at that time no spare part available, (it was already 7.30pm and they were closing so I kept driving with that condition until I am free to drop by the workshop). The mechanic told me still can drive but do not speed and it won't stall halfway (mati enjin). So I drove to 80-90 km/h max.
Then after 2 days the car stalled (mati enjin). Well not exactly mati enjin. Suddenly the car lost power, the engine did not stop, but when I pressed gas pedal, no response and engine warning light was shown on dashboard. (sometimes also show check oil and check battery lights)
Stopped aside as and luckily it can be restarted fine after resting for a few minutes. Slowly dragged it to nearest workshop.
The mechanic diagnosed the same thought.
1. Spark plugs
2. Spark plugs cable
3. Ignition coil.
He started the engine, pulled out the spark plug one by one with a long nose plier. Found 1 spark plug was not firing (sparking). Checked spark plug cable with multimeter, it is OK.
Then finally ordered a new ignition coil to replace
Problem solved.
Damage: RM 185.
Hope this info helps. Just would like to share back after Googling for information myself when I had this problem.