The truck will not idle. It run rough and will start and stall. At one point it had codes p2196 and p2198. When I get the truck going I notice that the front cats were glowing red. Found that the injectors were dumping fuel. Removed the spark plugs and the were black with soot. Ive changed the MAF sensor EGR and checked fuel pressure. The pressure was around 60psi and held pressure. (Had no drop. So no leaky injector or fuel regulator problem) I also drop the cats to see if they were clogged but the engine still remained the same. No difference with or without the cats connected. At the end I did a compression test and the cylinders on the drivers side were all around 120. The passenger side the compression readings were erratic. On one cylinder I had no compression then I would have 90. I was told that there is a timing chain in the rear of that head, and the guides break that can cause all these problems. Is this something that is common? Or should I look somewhere else before pulling this engine? Please help. This Explorer has a 4.0L SOHC
Yes it is common for them to fail. I would check the timing to make sure it is correct. As far as the cats, if they were glowing red, chances are they melted down, so they may need replaced when you get the thing going again.
As far as the compression, there shouldn't more than a 10% variation between cylinders. Yes, you could have a burnt valve, sticking valve. That may explain why you have compression one time and not the next. Start by checking timing. It could do the same thing. If it is good and correct, then you will need to start looking into the engine for possible causes.