Previa 96 Misfire help

[VultureSquadron]

 

My 96 Previa Auto had problems at idle, it would drop low then pick up again. I changed the ht leads and old plugs ( the plugs looked fine ). Now it misfires and is very difficult to start and does not run properly. The spark plugs are now very black.

[Paulscarbs]

First, check you have added the right type of engine oil - too thick and the crankshaft speed will be reduced (even more so in cold weather).

Check your starter is producing enough cranking speed to aid compression ratio.

Is the Battery up to spec and able to pump the starter adequately?

Are the glow plugs getting hot enough? These can be checked quite easily.

Is the glow plug module producing enough power to the plugs?

Finally check the fuel filter isn't blocked (black sooty plugs doesn't sound like it is though).