Can anyone suggest reasons rough idle and other strange iss

[MatesLeganza]

Early 90s carburettor Japanese car 1.6l..4a-FC engine

first sympton is general rough erratic idle, and pig-rooting and jerking a fair bit when at cruising speed and working through gears..

other strange symptom notices especially when cold or luke warm engine, was engine pulsed up and down rhythmically in engine idle speed , running in neat almost timed bursts at one engine speed, then dropping a couple of hundred revs and running at that speed, then back up again for a few seconds, then back down, etc etc etc.. slowing then speeding up, then slowing, then speeding up..I wondered at first if something had happened with the A/C idle-up solonoid, as the car has PS and A/C..

[benzino]

and your sure it's not a fuelling issue with the carb?

[Puddle31]

is it throwing any codes? how about your fuel filter? I have had mine run rough like that (no codes) and even shortly after a filter change. I changed it again and it has been fine ever since. it's a cheap and relatively easy thing to fix, especially if you haven't done it before. How many miles? When was the last time you did that?

[benzino]

Have you described your problems on the corolla forum?

[diomc]

have you tried the Idol air procedure, 1st take off idol ail valve and clean with Carb cleaner inside the air intake body use cotton buds. take off the small breather pipe the small pipe from the rocker cover to air intake, at the air intake body end clean out the pipe holder it should be blocked with back carbon, use a pin or similar you must clean until the pin can be pushed through into the air intake body that means you have all the blocked carbon out, once the idol air valve and intake are both clean, replace everything, then remove the battery neg cable for about 1 min. replace, sit inside car, turn ignition on for 5 secs, turn ignition off 5 secs, turn ignition on 5secs start the car engine, leave to idol until engine reaches normal temp. while engine is running turn on air con 10 secs, turn off air con 10 secs, turn on air con 10 secs , turn off air con , and turn off car engine car should run and idol normally.