Check Engine Light - ON

I have a ‘99’ Merc. Grand Marquis (75,000 miles). It started running ruff (took it to a Firestone store for repair and what a joke. another story)

I brought the car home w/ no problems. A friend had a code palm reader that stated codes 0171 & 0174 needed addressed. I proceded to change the front 2 O2 sensors in the exhaust manifold and changed the plugs also and an ignition coil in # 8 cyl. ( found H20 and oil in that spark plug port and the one right in front of it. Cleaned both out before changing the new plugs). I also replaced the intake manifolf since the thermostate housing was leaking H2O( All one peice and plastic). Check Engine Light came on (same code numbers came up again- proceded to change the O2 sensors in front of the Cat. Conerters. Check Engine Light came on (same code numbers came up again. What else should I be checking?

You need to resolve the issue why two of your spark plugs where both oil and coolant fouled.

Check the post again. The OP didn’t say the plugs were fouled with oil an water, he said the plug PORTS had oil and water in them. I’m sure he means the recesses into which the plugs fit.

The O2 sensors are telling you that the mixture is wrong. Why shoot the messenger?
There are proper steps the troubleshoot this problem. However, if you wish to just keep guessing and throwing parts at it, the MAF would be a good guess. Try cleaning it first. Also look for any vacuum leaks.

I had checked all the spark plug ports (recessions)last night and all dry as a bone. I thought the water might have been coming from the cracked Thermo. housing that was apart of the intake manifold (traveling back there when driving). I aslo changed the MAF Sensor the week before.

Will check for vacum leaks tonight Thks to all, will update tomorrow.

There was a well-publicized recall on the plastic intake manifolds on Ford 4.6L engine. Sounds like your’s has split.

It wasn’t a recall, it was a warranty extension. (They didn’t have everybody come in and get their manifolds changed. Instead they paid to replace any that did crack up to a certain date/mileage, or refunded you if you had already paid for it.)

You should be checking for:…vacuum leaks to (into) the intake manifold. There are several different ways that extra air (which will lean the fuel/air mixture) can get into the intake: a cracked, or poorly sealing, intake manifold, for one. Others are vacuum hoses which leak or go to components which leak (such as a ruptured brake booster), a leaking (or, stuck open) egr valve, leaking (or excessive flow) through a pcv valve, etc.
An inexpensive test vacuum gauge is your friend. Use it to check the vacuum in the intake manifold—with the engine running. If the vacuum indication is low (maybe, less than 17 inches vacuum(?)), go after those vacuum leaks.
If there is any place, on the outside, where you suspect a vacuum leak, you could swab that area with RTV Sealant. Ask for it at auto parts store.
Here is an excellent tutorial to show you what to expect to see on the test vacuum gauge: Click on the green highlighted Scenarios.

I changed the MAF sensor to start w/, a week before I changed the plugs. I will look at the vacum system to night. I had also changed the fuel filter last year.

I had the Vin #'s and did a check a 1 1/2 yrs ago to see if there was any recalls and non had shown up.

Thanks will play with it tonight, I also figured I would have to change the O2’s and the plugs in the near future anyway.