'96 Windstar coolant loss & cylinder miss

[holabr]

I have a 1996 Windstar 3.8L with about 62K miles. In September 2007, it developed a mysterious coolant leak that required replacement of a gasket behind the timing chain cover. Now I am again losing coolant with no signs of a leak. The oil is clean and I haven't noticed the smell of antifreeze like I did occasionally with the previous problem. I now also have a CEL with a P0303 code. I took it into the shop today to have the lower intake manifold gaskets checked and possibly replaced based on this being a common problem with Windstars. The shop did a pressure test on the cooling system for an hour and could find no loss of coolant or drop in pressure. The shop had no explanation for the coolant loss other than there may have been some air pockets from the last repair and since I only checked the coolant because the heater wasn't putting out enough heat, it may have been low for some time. As far as the P0303 cylinder 3 miss and an occational hesitation on quick acceleration, the shop suggested new plugs and wires. As you can tell from the mileage, the van does not get a lot of use and most are short trips to the store.

My questions are:
1) Does this all sound reasonable?
2) Is a coolant pressure test a good indicator of head or manifold gasket coolant leaks?
3) Should I add a can of Barrs Leak sealant even if a leak is not apparent?
4) Is it reasonable to replace plugs and wires at this mileage? I thought they were supposed be good for 100K miles.

[tripletdaddy]

1) Does this all sound reasonable?
Yes
2) Is a coolant pressure test a good indicator of head or manifold gasket coolant leaks?
Yes-probably the best method
3) Should I add a can of Barrs Leak sealant even if a leak is not apparent?
Maybe you should give it more time to burp out any remaining trapped air in it. You didn't say how long ago was the previous work done that introduced air into the cooling system. Top off the af to the full cold line and watch it for a month. If not sure it is not leaking, then try a stop leak that is a powder. I think that one is better and some others are bad.
4) Is it reasonable to replace plugs and wires at this mileage? I thought they were supposed be good for 100K miles.
At the very least, your plugs may need replacing. If the type of driving is considered "severe duty," eg. lots of idling, lots of short trips - basically hardly any long range driving and mostly block to block and light to light travel, then your plugs will have lots of hours and not the greatest conditions, so they may need at least checking for gap and wear. I'm not so aggressive about replacing wires. I look for arcing at night with hood up, look at general condition and check for resistance to be around 5000 ohms per foot.

[wiswind]

I would also put a can of Berryman's B12 Chemtool into the gasoline.
I have, more than a couple times, picked up a slight miss.....and later found that it was some sludge buildup over the spray end of the fuel injector(s).
The Berryman's is the only product that I have found that will clean that.
I have tried Techron and a bunch of others.
Good new is that the Berryman's is one of the cheapest fuel system cleaners on the wall of many choices at the auto part stores.
The one I get is in a metal can.....might take 2 cans to treat 1 tank of gasoline.

Another possibility is clogged EGR ports...which normally start clogging nearest the EGR valve first......and leaves Cylinders #3 and #4 the last ones open.....getting all the EGR flow.....which starves that cylinder for oxygen.

To test for the EGR ports causing the misfire...(this WILL cause the CEL to come on for lack of EGR flow....as you are disabling the EGR valve).
Remove and plug the vaccum line that goes to the top of the EGR valve......go for a drive...
If the vehicle does NOT have the misfire (you should feel the motor miss....and the CEL will be flashing while it is happening) then you will need to remove the upper intake manifold and clean the EGR ports.

IF the misfire still happens....then it is not caused by clogged EGR ports.

Reconnect the vaccum line to the EGR valve......as you don't want to try leaving it disconnected as a solution.....just a temporary test to diagnose the cause for the misfire.