Can you change just one injector or do you have to change the whole spider? I have a misfire and I've changed plugs wire etc. So figure its the only thing left.

 

You have to change the whole spider.
Before you "figure" anything, do a fuel pressure test/ leak down test. Do a search for that and you will find out how.

 

Yes you can replace a single injector poppet. However do you have a random or cylinder specific misfire?

 

You can? That is news to me.

 

While you can replace a single injector, the chances of having only one injector causing your problem are somewhat remote and the chances of having the same problem sooner rather than later on the other cylinders if that is the case is very high. Once you go past having to replace two injectors, you might as well replace them all as the cost isn't that much higher to just make the jump to the updated MFI spider.

If you haven't already done a cylinder compression & leak down test, then you should do that before coming to the conclusion that the injector is at fault for the concern. Without those results, you don't know if it is a compression leak through a bad piston ring (or ring seal), bad valve, etc that could be causing the misfire.


I have even seen high carbon buildup cause misfires in these engines in the past due to the heat concentrations that they allow. The heat concentration can cause pre-ignition which is read by the PCM as a misfire. Carbon buildup in a single cylinder can be caused by faulty valve seals among other problems.

 

I did check compression on the cylinder in question. I'm getting a misfire on #4,wile playing with wires and cap etc. It did jump around a couple of times,but it has start and ended up back on #4. I just had to replace the fuel pump. It was running fine before that,I did check the fuel pressure and there was no leak. I've been work on this thing since dec 23, I've almost had it.

 

Yes, just finished replaceing the #4 injector and its running smooth as silk. I wish I would have checked that sooner.