OK, I have a 1994 XJ 4.0 and it is backfiring through the intake, cat glows red and the oil smells like gas.

Here is what I have done,

Changed all plugs - it was fouling plugs
Once all plugs were change I ran it again and noticed that CY-1&6 were black fouled and 2-5 were white fouled(lean).
I immediately thought injectors, so I switched 1 with 2 and 6 with 5, to see if the fouling changed from 1 and 6 to 2 and 5.... It did not, even with the injectors swapped around I still get black-foul(rich) on 1 and 6, and white(lean on 2-5.

I have compression tested each cylinder and all of them are over 135, with no less or more than 15 psi difference from each cylinder.

All grounds have been pulled, tightened and cleaned


The distributor has been replaced, I have checked the timing and it is sitting correctly now but still backfires through the intake and causes the cat to glow red.

I have also replaced,

MAP
O2
IAC
Coolant temp Sensor
Fuel Pump
Fuel pressure regulator
VAC Lines

The engine sat for 2 years before I bought it and now I am trying to get it going again, but I am running out of ideas! Help please!

 

Are you sure you have the plug wires connected in the correct firing order?

 

Another thought:

Are you sure you indexed the distributor correctly when you reinstalled it? Being one tooth off might do what you described.

 

Definitely an ignition problem. I'd stick with making sure your timing is right and your plug wires are ran properly.

 

Well going by your thread title here "Oil Smells like gas, misfiring, red CAT" and you do indeed have the distributor in correctly, then it very well could be a timing chain issue. Need to bring it up to top dead on the compression stroke with the sparkplug out (using the piston as the reference) and then look to see where your timing mark is lined up with the harmonic balancer. If it is a long ways away from the TDC mark it could be the chain.

But the distributor or wires would be the first direction as already suggested.

 

It seems like it would pretty much have to be a timing/ignition problem. The backfires are from the plugs firing while the intake valves are open. The fuel in the oil and the fouling patterns would indicate that the plugs are firing at the wrong time with respect to the fuel spraying into the cylinders. Fuel and spark are somehow out of time with each other.

I would change that oil as soon as you get the timing issue solved. The fuel in it can't be doing the motor any favors.