I have a 1990 Toyota pickup with the 22R engine (carbureted), and recently it started idling very low and shaking at idle. Work done in the last year, other than brakes and oil:
- Carb rebuild
- New plugs
- New plug wires
- New fuel filter
- Fuel pressure tested, all good
- Compression tested, also good
- Ignition coil tested, good spark to all leads out of the distributer cap
I know the idle mixture screw is set to the correct factory setting, and the idle screw is adjusted properly to 700 rpms.
- When started cold the engine will usually die within 3-4 seconds and then upon restarting I have to hold my foot on the gas for 15-20 seconds to keep it from dying.
- It will occasionally idle at 700, but will also drop to 600 and even go up as high as 1250 sometimes.
- The shaking goes away if I hold the rpms above 700.
- When it is idling low, getting moving in first gear will cause horrible jerking, that feels as if I'm repeatedly stepping on the brake, but once I get up above 15 mph or so it will drive nice and smooth, with no misfires or jerking/hesitation. Edit: -New observation, every couple seconds I can hear a ZAP sound, I checked and there's no spark arcing at the boots of the wires on the cap or from the wires to the engine, it's got to be inside the distributor cap right? If it sometimes arcs to the wrong cylinder would that account for the backfiring thru the exhaust and the terrible vibrations at idle?