I have a 99 Deville that has a misfire p0300 i've done a spark test and all8 cylinders have spark. Ineeded toreplace the starterso whenI removed the intake manifold I noticed #2 cylinder had a redish pasty wet material in the intake port underneith the intake manifold. Could that be a bad injector not firing causing themisfire because all of the other ports are nice and shiney accept for#2. Any helpon this matter would be greatly appreciated.

 

I'm not familiar with your engine but if the leak is blowing hot exhaust gasses onto a spark plug lead it could be that the lead is now not working properly. If you have a spare set of good plugs then start by changing them and see if the missfire disapears. Try also changing over two of the plug leads, take one from a good cylinder and put it on the number 2 cylinder, obviously change over at the distributor end to keep the firing order correct. If it's the plug lead then #2 cylinder will stop missfiring and the other cylinder will begin to missfire. Also check the leads are clean and that no spark is tracking to earth. To do this open the hood on a dark night with the engine running and see if you can see a spark escaping to earth on the #2 lead. It's a process of elimination really, try one thing after another and see if it works.

 

I have a 4.6L I did a spark teston all the leads and they passed so my next thingI thought was maybe the injector is bad