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When I put my '94 4.6 into drive first thing in the morning, the revs have started dropping really low for a brief instant, and the car almost (or does on occasion) stalls. It has become more noticeable in the last few weeks as the temperature is around freezing when I go to work. The car starts ok when warm and drives fine at all other times, idles at around 600 in drive when warm and doesn't missfire etc.

Do you think I have a problem somewhere, or is it just the cold weather making all the oil thick creating more drag...? After reading some other threads on here I checked all the vacum pipes on the engine. They're all attached, although some look a little old.

The plugs and air cleaner haven't been changed for around 7000-8000 miles. Could that have somethng to do with it?
 

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It could be thick oil, what weight do you use..? I use 10w40 and she never has a problem even 15 degrees sometimes. I do recomend letting it idle for 5+ minutes on cold mornings, don't just start and go.

Your idle sounds fine and normal, BUT how far does the rpm gauge drop when put in D or R..? It should drop just under 500rpms for a second then return. DEFINETLY check the air filter, bang it out on your knee if you don't have the time to get a new filter (i prefer fram).

The plugs i wouldn't worry about. Honestly the cold weather **cks with cars ALOT, i think it's just the cold...
 

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I've just changed my oil. I think it was 10w 40 from memory. I use Castrol GTX (dunno if you can get that in the states), but it happened the same before I changed it. The revs drop just below 500 when I put it drive normally. If its going to play up, it drops below 500 and either coughs and dies, or coughs and just about hangs on running. I kinda thought it might be just the cold.

I'll check out the air cleaner at the weekend. I've got a spare so thats no prob.
 

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Check the IAC valve. It is what the computer uses to control idle. It might be dirty or could just be slow. Also check your throttle body and make sure its not all gummed up.
 

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let it warm fur a minute or two
 

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I agree check the IAC valve it might have crap in it thats not letting it function correctly when cold

-Matt-
 

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My money is on the IAC valve. My car did WEIRD stuff, with the idle, in cold temps when it went out. Anything from dying, to a loud noise coming from it... to reving up to 2000rpm and then dying lol. I let it go for a long time and it just got worse and worse.
 

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Discussion Starter #8
Would I be right in thinking the IAC valve is the small cylindrical thing at the rear of the inlet manifold on the drivers side? Can I just unscrew it, clean it up, and refit, or am I gonna need a truck load of computers to set it up again? What does it do anyway?
 

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Andy625UK said:
Would I be right in thinking the IAC valve is the small cylindrical thing at the rear of the inlet manifold on the drivers side? Can I just unscrew it, clean it up, and refit, or am I gonna need a truck load of computers to set it up again? What does it do anyway?
thats it exactly. I don't recommend cleaning and putting it back on, best thing to do is replace since they aren't exactly that expensive. And, all you need to do, is go buy a new one and carefully put it back on and start the car.

The IAC controls the amount of air allowed into the engine at idle speeds, or that's how I understand it.
 

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Andy,
Don't touch anything - your car's fine. Mine does just the same in this cold weather. Just let it warm for about a minute or so before engaging drive.
Once you start fiddling with bits like the IAC etc., you might end up needing parts you didn't need and might not be easy or quick to get over here, either.

Dave.
 

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Discussion Starter #11
UKbird said:
Andy,
Don't touch anything - your car's fine. Mine does just the same in this cold weather. Just let it warm for about a minute or so before engaging drive.
Once you start fiddling with bits like the IAC etc., you might end up needing parts you didn't need and might not be easy or quick to get over here, either.

Dave.
Thanks Dave, I'm living with it at the moment, but its started stalling on the odd occasion now too. I'll see what happens when the weather improves. It drives fine the rest of the time.

I just ordered some stuff from the states, maybe I should have ordered one of those too to keep in stock. Nevermind!
 

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Darrin said:
Thats the classic symptoms of a sticking IAC
Thanks, Darrin. I'd better get on and order one then I guess. At least I know what the problem is now. Thanks.

Sounds like you need one too Dave!
 

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mine does it too, I just replaced the IAC though, I also had other problems though, gonna clean the MAF this weekend and see if that helps me...
 

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You know... Your problem just could be your battery getting old. When a 94/95 is low on power it can run bad... After the car charges a little she has enough oomph! If this is the case I would not run out and replace the battery right away... It still may have some life...

Conversely do not run out and buy an IAC valve on a whim. Test it first. Check out my TSTaCC IAC tech Article!
:D
 

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Also check out the ECT engine coolant temp sender for the computer not the gauge the 5.0 was doing the exact same thing replaced sensor corrected problem. Ecm thought the motor was warm all the time never went into cold start/run strategy stayed in warm all the time.

Iac will affect the way it runs all the time not just when its cold.
 

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Yeah, don't go out and buy any parts yet. Just do yourself a favor and pull the IAC and clean it. Its not too bad to do and will tell you if thats it or not. If cleaning it works then order you a new one.
The IAC is an idle air controller. Its job is to control idle air. It can affect the idle cold and hot. Either or both. It sits in the airpath and on a 10 year old car it can be pretty nasty in there. I bet I see more of these gunked up and stuck on this age car cause this problem more than all of the rest of the potential problems put together. This comes from actual real-world fixing other peoples cars for a living experience, not from a book.
It could be the battery. Test that too. It could be the spark plugs, wires, a cracked hose or other air leak... Heck it could be a lot of things. But if you have ever seen the insides of an intake that has been on a car for 10 years then you understand how likely it is that your IAC is getting gummed up. It will never hurt to clean it. I just wouldn't keep one that you freed up on there if it were me.
Good luck with it.
When in doubt about a mechanical problem with your car, ask a mechanic :)
Darrin
 
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