Slight miss at idle...'99 Windy 3.8L

[65val]

Originally Posted by 12Ounce

I'm inclined to suggest a upper intake manifold removal, inspection, cleaning with replacement of all gaskets and seals involved. Work from the top. Remove the wipers and all the cowling. The idea is to do an inspection of as much of the engine's "top" and engine box as possible ... all without really doing a lot of invasive, scary engine mechanical work. The problem may be almost anything ... but you are very apt to find whatever it is with a bit of looking. It will give you a good opportunity to inspect, clean and lubricate a number of details .. such as the EGR injectors, the IAC valve, the synchronizer, the ... etc, etc. And Yes, inspect all the electrical harness you can get your hands on while in there.

I've just changed my engine oil at 471,000 miles ... and I'm about to do exactly what I've suggested above to my ole Winny. It won't be the first time for me, so I have a secure comfort level, but I've picked up the leak codes recently and I also have a bit of power loss and poor idling. Just received my gaskets from Rock Auto ... so its time for this old bird to get busy!

... jump in and good luck!

Thanks 12Ounce....Never had the top off this 3.8 as yet, so can you tell me what gaskets I would need to replace to do what you're describing? I've already cleaned the IAC and EGR valve (it holds pressure so I assume its OK), and checked all the EGR vac lines.

[tomj76]

You'll need the lower gasket set, Felpro P/N# MS90812

However, these are "rubber" gaskets and often can be re-used. Other gaskets associated with the upper intake manifold are the IAC motor gasket (Felpro #71428, possibly Motocraft CG765 instead) and the throttle body gasket (Felpro #61046), also both rubber and can be reused. It is not necessary to open the joints associated with these gaskets to remove the upper intake, so you may not need them.

You will may also want to replace the Intake Manifold Isolator Grommet Set (Felpro #ES72204)

[65val]

Thanks Tom. The "Lower Plenum Set" was replaced in 2006....that would be the intake manifold to cylinder head gaskets, I assume? Is that the set you're referring to? Do they need to be replaced at certain intervals? The van only has 140,000kms (87,000 miles) on it.

[tomj76]

Sorry, that's a typo.. it's just the intake plenum set. It has 6 gaskets to seal between the metal part and the bottom plastic part, plus a large gasket to seal between the upper plastic part and the lower plastic part. I think I got a little confused because there is are two pieces to the plenum, one on top of the other.

If you had the metal part off, then you should have removed the plastic parts to access those gaskets as well.

I'm not aware of any maintenance schedule for these gaskets, but I've read that intake manifold gaskets and even head gaskets have a lifetime (number of temperature cycles), caused by the movement between the various parts created by thermal expansion effects, and the abrasion of the surfaces against the gasket material.

FYI, I think on your 1999 they call the top plastic part the "upper plenum", and the lower plastic part below that the "middle plenum", and the metal part the "intake base", based on the naming used on the Summit Racing website. On my '96 the plastic intake is not in two pieces, so I've been calling it the upper intake and the metal part below the lower intake.

[65val]

No problem...thanks Tom. I didn't do the lower gaskets back in '06....this was my fathers van back then and he had it done at a shop.

[12Ounce]

Yes, I was suggesting dealing with the upper manifold only.

Its easy to get tangled up in terms when talking about engine parts and the manufacturers themselves make it more difficult ... seeming to never really settle on ONE name for a particular piece.

Lets call the "lower intake manifold" that aluminum piece that covers the open block and fills in the "VEE" between the two heads. It has two engineered full-length gaskets and end seals that seal it from the heads and block. IT HAS COOLANT FLOWING THROUGH IT. It also has the "runner control" (don't ask!) as part of it. Therefore removing/installing the "lower" is a whole bunch more work/trouble than the pieces mounted on/above it. Unless you see coolant and engine oil being mixed ... lets leave it be. Even if you have to come back and remove it later ... I would leave it alone for the "first time through".

The plastic "middle" is held in place by 8 complex bolts with grommets. There are 6 engineered gaskets individually sealing the 6 air passages. Incidentally, the throttle body is mounted to this "middle". The plastic "upper" or "plenum" is merely a cover that helps channel and smooth air flow. It is held in place with a dozen or so simple bolts and has an engineered perimeter gasket.

As the engine whips about in its ever softening motor mounts, this mass of intake manifold is trying to be shaken off the engine. Especially with the air intake bellows adding its strain. If the lower is successfully mounted, it will stay in place fairly well. But the rest is essentially mounted in rubber ... and will eventually fail. The grommets between the middle and lower seem to suffer most. Once they fail ... any of the associated air gaskets can begin leaking.

So usually the grommets MUST be replaced. The gaskets can often be reused. They are engineered to be installed dry, but I am becoming more and more fond of using Permatex sensor-safe Gasket Sealer on grommets and gaskets.

[Mustang_Driver]

like i mentioned above it doesn't take much time as you have the plenum and all the other stuff off anyways another 3 bolts might solve some headache this was my problem once it got warm while driving it felt like the trans was letting go as it was bucking like a horse

[65val]

Well guys...I changed out all the upper plenum gaskets, isolater bolt grommets, cleaned the EGR ports in the manifold and checked all the vacuum lines and hoses for cracks/splits etc. Nothing found and the miss is still there. There was a bunch of oil in the upper plenum, so I cleaned all that out and replaced the PCV valve as I thought thats the only way to get oil into the plenum...no change. I guess I may have to check the coil pack, but that doesn't seem to have the right symptomology for this miss. The miss started after a backfire during a cold start, and other than the miss, the van performs normally.

EDIT: I went out and observed the engine running in the dark and saw no arcing at all.

EDIT#2: I pulled the coil pack to check resistances...on the low side I get 0.08 on all 3 terminals, and on the high side I get 13.2 on bank 1, 13.1 on bank 2 and 13.0 on bank 3. Are these proper readings?

[Mustang_Driver]

Not sure about the coil high and low sides but i do have a Digital copy of the haynes manual that i was given but i no longer need and you can have it if you want it i am working on my escape at the moment so the windstar is being put on the back burner as i need to completely redo the front end and the quote was more than the van is worth but i still need to either fix it or scrap it

[12Ounce]

You've made progress by eliminating a bunch of stuff ... good work that you can check off the maintenance list.

The ohmmeter readings seem OK, but strange things can happen when voltages are so high. It would be a perfect time to use an inductive timing light it you have access to one: While the engine idles, test each spark lead to see if all have the same result (triggering the lamp). One plug, or cable, or coil path; with a leak to ground, can be trouble.

??

[12Ounce]

Another thing to try: Take an artist brush and daub some high-temperature grease along the seams formed by the lower intake gaskets and end-seals. Also swipe the runner shaft journals.

Don't use so much grease that you make the engine super-flammable, but try to guarantee that the block doesn't have a vacuum leak. That big miss fire may have blown a hole in a gasket!

[65val]

@Mustang Driver Thanks for that link...I already had that, but had forgotten I did...Thanks for the hint!
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@12ounce Checked all 6 ignition wires with inductive timing light...all flash normally...and used brake clean to check lower intake gaskets(between metal intake and heads)...no change in engine running. I tightened those when I had the plastic plenums off.
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Also not sure if I mentioned earlier, I'm getting no codes at all. I had a P1401, which is the DPFE sensor (high voltage), and I replaced that to no avail.

[12Ounce]

Wow, you are covering the bases!

Its a bit of bother, but could you do a compression test with the throttle plate blocked open while testing each and all cylinders?

[12Ounce]

....and have you already done this one: disconnect and plug the control air tubing/hose that feeds the EGR?

[65val]

Originally Posted by 12Ounce

....and have you already done this one: disconnect and plug the control air tubing/hose that feeds the EGR?

Yes...disconnected the EGR vac line....went for a drive...Check Engine light came on...got a code (EGR flow insufficient)...cleared it this AM and reconnected the EGR hose....miss still there. Nothing I've done so far seems to have affected the miss at all.