why does my car engine shakes on idle?

1992 NISSAN SUNNY
230,568 MILES • 4 CYL • FWD • MANUAL
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KPRATAP
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i just replaced my carburator because it was consuming fuel like hell 30litre did only 200km. Now ihave replaced my carburator and it consumes 8 litre for 100km. But thd problem now is that when i start the engine it shakes and vibrates i did adjusted the idle screw but it didnt help. The RPM meter reads below 1 and above 0.5. when the engine vibrates thje RPM needle on the meter flactuates from 0.5 to1. please help because its very hard to find a carburator experienced mechnics here.
Aug 29, 2011 at 7:13 AM
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DRCRANKNWRENCH
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There are few possibilities, some are tune-up related;
Spark plugs
spark plug wires
vacuum leaks
Intakes sensors
O2 sensor
Fuel system need cleaning
Idle Air Control Valve (IACV)

To start get some fuel system cleaner. I only use SEA FOAM or BG44K. They are around $20 a can but nothing else works like them. They work so well that the oil will need to be changed after running 2 cans, (that is what I would suggest), that it will make the oil dirty with all the deposits it cleans out.

Try that and let me know how it goes. I will watch for your post and get back ASAP


Aug 29, 2011 at 7:38 AM
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KHLOW2008
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Have you adjusted the air/fuel mixture?
Have the valve clearances checked/adjusted
Aug 29, 2011 at 2:07 PM
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KPRATAP
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thanks for the reply.. i have changed the fuel pump,spark plug wires and spark plug. buti dont know where the valve clearance,vacuum leaks
Intakes sensors
O2 sensor
Idle Air Control Valve (IACV)
are located as you know that the mechnics here dont know much about carburators and there might spoil its tunning since i think the air and fuel mixture is ok since the fuel mileage is ok 8litre does 100km. i have replaced the fuel pump and the filter so i think it is ok. what should be my next step?
Aug 30, 2011 at 8:27 AM
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KHLOW2008
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Carburetted engne do not have any IAC. The air fuel mixture screw is on the caburettor.

Valve clearance is under the valve cover. You need to remove it to check.
Aug 30, 2011 at 9:11 AM