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'94 4.6 sometimes idles funny

'94 TBird LX V8, 66k nursed (mostly city) mi. Only parts that are not original are plugs, wires, air filter, battery, and MLPS.

The idle is lately doing unexpected things every once-in-a-while.

For instance, today I started it cold, waited 'till the idle came down from 1100 to about 850 rpm, put it in N and coasted down my hill. Bottom of the hill, I shifted into D and it revved up. I shifted back into N: it got up to 1500 rpm (gas petal was never depressed). It calmed down and ran normally thereafter for about 16 mi. It was about 50 F outside today.

Does this sound like the IAC? If so, should it be cleaned? Replaced?

Anybody know of a picture or diagram of precisely this 4.6 with pointers to the common replaceables (EGR, IAC, etc) on the net?

Thx, Puddin'

"Well, there's two trains runnin'. Ain't neither one goin' my way. One run at midnight, the other run just before day." - from "Still A Fool", Muddy Waters, maybe 1949

Reply to
Puddin' Man
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Apologies to the group if this shows up twice. Once with a picture as an attachment. Brain fart.

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In my experience the IAC caused my 4.6 to die, wouldn't idle. But its easy to clean. I would start there and see what happens. I have had luck with just spraying WD-40 down in where the spring is, let it sit for 10 mins or so, if you have a small stiff brush and can reach down in there in can't hurt. Then blow it out and re-install. Mine is 10 years old (167K) and still works fine. (as long as I clean it about every 12 months or so).

The next easiest thing to clean (and save $$) is the MAF but that usually is needed when it starts to ping).

Reply to
F.H.

Thanks, but it's not the same motor. I don't mean at the block/ heads level: the intake routing and throttle body seem to be different. Near as I can tell, my IAC is on the left not right side.

Sounds good.

Forewarned is fore-armed.

Thanks, P

"Well, there's two trains runnin'. Ain't neither one goin' my way. One run at midnight, the other run just before day." - from "Still A Fool", Muddy Waters, maybe 1949

Reply to
Puddin' Man

Hey Puddin' -

Go looking for a vacuum leak. My '95 CVic did something similar. I found a hole in a small hose connecting the PCV valve to the intake. The pipe is metal but has a stub of rubber at each end to connect. The piece closest to the engine has a bend in it. Mine had a hole hidden in the bend. Screwed idle up a lot but it was heck to find.

Might work for you.

PoD

Reply to
Paul of Dayton

Might be right. On my 4.6 the vacuum hose cracked right where it turns toward the throttle body. Cut out a section and stuck in a nylon elbow.

Reply to
F.H.

I'll put 'em under the microscope (figuratively speaking). Thanks, Paul.

Skoal, Puddin'

"Well, there's two trains runnin'. Ain't neither one goin' my way. One run at midnight, the other run just before day." - from "Still A Fool", Muddy Waters, maybe 1949

Reply to
Puddin' Man

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