Twice in a row I have had a shudder while idling and under acceleration on cold start up. Cleared up after a few minutes. Does not do it after warm up. Today it threw an engine code, misfire on cylinder 4. This is the 3.3 litre. Have just changed the egr valve. Could this be an issue with the coil pack or the brain? There is 274,000 kms on vehicle. Coil pack is $179.00. I don't have the equipment to diagnose a brain fault, so would this be a good place to start before I go to a dealership and get bent over the table? It seems to happen when the temperature is around 10 - 15 C and humid.
An update. I pulled the plugs to check for worn plugs. I installed iridiums 2 years ago and they are fine. I replaced the coil pack as a start. The Ecm may be next if I still get the shakes on start up.
I wouldn't jump to a PCM just yet. Check compression when cold and again when hot. A collapsed lifter can give issues like this, but it's rare. Sloppy timing chain tensioners can as well. Any rattling or ticking when it's misfiring?
I don't have the equipment to check compression. When it misfired it was just like the old days when you put the wrong plug wire on the distributor, shaking under acceleration. I'll give the new coil pack a while to see if this fixed the issue.