I have to look at diagrams to see if a similar design, but I will toss this out there. Long ago I had a Lincoln Mark VIII with the Ford 4.6L engine. Oil on the plugs and coil boots was a major cause of misfires and issues as the engine aged - it seemed even a little oil would cause the COP to ground out. With that engine there were valve cover tower gaskets that needed to be replaced to stop oil from getting down into there. I think the 4.4 Jag engine is similar. If you have oil down there, how did it get there? I would look into it and consider replacing the valve cover gaskets and "spark tower" o-rings or whatever they may be called.

 

Yes, 100%. I'd change out the plug/coil tube seals (valve cover gaskets too since you'll be in there already) or the same thing will likely happen again.

 

There was no oil on the ignition coil, and no oil in the spark plug hole. The oil was only on the spark plug electrode and threads which leads me to believe oil is getting past the piston rings instead of it being a spark plug well gasket.

 

Ah, that's important to know. I guess the oil could have still been there from before you cleaned the oil out of the intake, but I would think it would have burned off by the time you checked the fouled plug.... I guess it's just a wait and see if it fouls again type situation now?

 

Holy cow the whole intake manifold?! impressive- I still have my codes- but was able to get the wavier to get my LR3 through emissions. It is crazy how sensitive they are-

 

Ordering the seals to to it all the coming weekend.

Yesterday while fueling, I found my gas cap broken. The top is separating from the plug that goes inside. Ordered a new one.

Wondering how much, if anything that contributes to this since the light went off by itself then came back on before finding the broken cap. I’ve also noticed a marked drop in fuel economy and am almost able to watch the gas gauge drop.

 

As of the past month, I have seen my MPG drop from roughly 14 to 11.5 (ish). I have hit a pause on the issue as my main concern was the registration- technically without passing emissions i could not register. Now that is done, I have more time. I have the replacement seals for the fuel injectors, but now that you have shown the pics with the manifold smoke test, I was thinking perhaps I should do it in one fell swoop.

 

Quick little update. CEL is still on. Light comes on and goes off every now and again. This is leading me to believe there is definitely a minor vacuum leak. I have done a propane test, I have used WD40 and carb cleaner. All too no evident reactions. I’ve replaced many hoses and gaskets. I think all that remains is the brake booster and associated vacuum hoses.

i do want to ask. After the engine is warm I can definitely hear a vacuum sound. Very pronounced too. Is this normal for this engine? I can’t pinpoint the area.

 

The very pronounced vacuum sound after engine is hot could be your PCV. They make an obvious hissing sound when working. Only vehicle I’ve ever had like that.

I think you’ll need to do more diagnostics to find your problem. Intermittent will be difficult. Are you getting the same trouble codes? If it is coming back regularly you will want to try triggering it and then doing your diagnostics once the CEL has returned.

edit: just went through the whole thread. There are 3-4 different owners chasing lean codes. It’s very confusing to track who has done what. Coldwater, it doesn’t look like you ever did a smoke test? Start there!

 

Could be the fan running, too...