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issue testing IAC -- how's this reading look


guevera

New Member
Joined
Mar 8, 2008
Messages
1
City
NorCal
Vehicle Year
1994
Transmission
Automatic
First:
new member and want to say hi and thanks to everyone for this forum -- you're information has kept my Ranger running, saved me tons of money and time, and led to more busted knuckles than I can count.

On to today's problem:

I've got one of those classic Ranger driveability problems on my 94 4.0 4x4.

The minute I first put it in gear to pull out in the morning I start getting a very low RPM idle combined with rough running engine that feels almost like it's missing. It smooths as RPMs and speed increase, but the idle stays rough whenever engine's on. It's also not noticeable when I first turn the engine over in the morning; but becomes apparent when I put it in gear.

I believe it's a bad IAC valve. The hayes manual says to test with ohm meter and resistance should be 7-14, the resistance as displayed by my cheap, old, analog meter is 6.

Does that mean it's safe to say the IAC's bad? Or is that so close to spec that it's likely to be just normal variation combined with a cheap meter? Would a bad IAC automatically read something like 2, or 20, or whatever? Or is a six a normal reading for a bad IAC? Don't want to spend the cash on a new unit if I don't have to.

If it's not the IAC, what next?

Background:
The CEL isn't lighting up, so I don't have any codes. I've cleaned the carbon out of IAC without any big change. The plugs and wires are a couple of months old. The MAF sensor was replaced at the same time and is clean. I haven't checked fuel pressure, but I replaced fuel filter and pump (nightmare!) about six months ago. I pulled a plug and there's definitely more carbon on it than I'd expect for such new plugs, but not so much that I'm like "oh s**t"

Truck has 130,xxx miles on it.

Sorry for the long post -- just trying to cover the bases.

Thanks for the help.
 
If you disconnect the electrical connector from the IAC, does the idle speed change?

No change = bad IAC.
 

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