Oil in upper intake and misfire.
 

I have a 1995 GMC Jimmy 4.3L. While driving home form work it developed a misfire. I bought new plugs. I have not replaced them yet because i wanted to try to find out why the misfire happened. I pulled the plenum off today and could smell gas. I do not see any fuel leaks and fuel pressure is fine. There is oil under the plenum on both sides. Would the oil leak down to the cylinders and foul the plugs? I know the transfer case switch needs to be replaced, so could the oil be transmission fluid? It is black in color. Could it be transmission fluid mixed with the carbon build up in the intake?

This is what I have replaced in the past year:
spark plugs
wires
distributor cap
Rotor button
fuel injectors (spider injectors)
fuel tank
fuel pump
sending unit
fuel tank
fuel filter

Any help would be appreciated. Thank you.

Update: Changed the plugs. Changed the fuel lines inside the intake. Cleaned the carbon buildup I could get out of intake. Still has misfire. Any suggestions?

Any codes? You can try to clean the EGR valve and see if that fixes your issue.

What brands did you use for all of your parts. These things are picky

Thanks richphotos, The Check engine light is flashing. I have tried to get the codes but I can't find anyone with a reader that will read the codes. I forgot to put it in the list above that I have changed the EGR valve and the O2 sensor also. I did pull the EGR valve and check it the other day when I had the intake apart. As far as the brands, the only one I am sure about are the plugs. I had put Champion plugs in and I put AC Delco in last week because i kept reading on here about how bad Champions are.

Flashing CEL is indicating the active misfire. Check your ignition coil and check distributor for wear/play.

You can get an OBD1 code reader online pretty inexpensively. Just make sure you get one that is set up or has the adapter for GM.

Thanks Pepsibottle1, I had thought about the coil but i did not know if the coil would just stop firing to all the plugs or just 1. So if it is the coil could it cause random misfire on different cylinders?

Thanks rockp2, I will check those out.

Just saw one at the auto parts store also. Didn't take notice to how how much it was.

start it up tonight, in the dark, underhood light off. Look at all the spark plug wires for arcing/sparks. could be bad wires

how to check codes for free :

a little oil in the manifold is normal. How clean was carbon build up? its normal for it to be black is nasty. If there is a fuel leak then you will have cleaned washed areas since gas is a solvent.