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  #1  
Old 01-24-2011, 03:40 PM
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Default Fluctuating Low and Very High Idle

My 1996 Ranger idles extremely high and then so low it almost stalls for quite a while until the engine warms up. Once warmed up, it seems fine.

Now that the cold weather is here, the high idle has gone to extreme...like 4000 rpm for 5 to 10 seconds. This can't be good as the oil is thick when cold and I don't need to starve the bearings.

I suspect the Idle Air Control Valve, but I've researched this a bit and I don't seem to be having quite the same symptoms as people who've had IACV problems.

There are a few codes, but nothing major. One says the engine is running a bit lean, and another referrs to the Purge Canister Flow is non-existent (and that unit is solidly rusted), but neither seem related to the high/low idle issue.

Any thoughts on the matter?

ps: MY next step is to try cleaning the IACV, although my book says not to use solvents. Not sure what they cost from Ford, but the after-market one lists for $144 here. So if cleaning it helps, then I"d feel better about spending the $144 on this old truck.
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  #2  
Old 01-24-2011, 03:59 PM
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Default Re: Fluctuating Low and Very High Idle

well i saw an episode on truck universe about rangers having an idle problem. It has to deal with idler air control know as IAC. its on the back side of the throttle body. When you take it off you can just clean it and re-use it and its better to re-use it if you have a stick. Make sure to grab the rubber gasket and dont drop it. spray a little lube in it swish it around clean it out and it should work i would try this to see if it helps a little bit, cus then you know if its the prob or not or buy a new IAC. not sure if its the problem but it might work.
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  #3  
Old 01-24-2011, 07:58 PM
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Default Re: Fluctuating Low and Very High Idle

Tap on it when the idle is high & see if it all of a sudden it idles down. If it does replace it. It'll happen again. Ford had a problem with them somewhere around the model year of yours & had a program repair for that.(not a recall but a program) Their repair was to replace them because the problems always came back. If that's the problem & the next time you change oil you'll wished you did when it runs up to 4000 rpm without oil pressure for a few seconds.

----------

It also sounds as if you might have a vacuum leak if it still shows to have a lean code. as info. Good luck.
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Last edited by 1KOOL1; 01-24-2011 at 07:54 PM.
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  #4  
Old 01-25-2011, 10:29 AM
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Default Re: Fluctuating Low and Very High Idle

IAC's are known for hating cold weather. Autozone sells them for $45.

As far as a high idle, is this when you're driving or when you first start the truck up? This sounds really stupid, but it has proven true many times. Ford Rangers and Explorers have a problem when it comes to distance between the brake and the gas pedals. If you are a member of the size 12 and up shoe club, then you need to watch your footing when you're at stoplights. It is very possible to have your foot halfway on the brake and halfway on the accelerator. I had this problem myself, and when I looked at my putting one time when ythe idle skyrocketed, I saw that my foot was halfway on the gas, and when I moved my foot farther onto the brake pedal, the idle dropped down.
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  #5  
Old 01-27-2011, 08:21 AM
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Default Re: Fluctuating Low and Very High Idle

It's only when it's first started. Once warmed up, it's fine. Not a foot problem either, although I can see why you mentioned it.

Oddly, it starts and idles fine the odd time, but generally it's quite extreme in fluctuations.

No Autozone around here. I'll do some more tests and also try cleaning it just to confirm things and then bite the bullit and spend some cash.

Thanks Guys.
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  #6  
Old 01-27-2011, 08:48 AM
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Default Re: Fluctuating Low and Very High Idle

Quote:
Originally Posted by Fordzilla80 View Post
Ford Rangers and Explorers have a problem when it comes to distance between the brake and the gas pedals. If you are a member of the size 12 and up shoe club, then you need to watch your footing when you're at stoplights. It is very possible to have your foot halfway on the brake and halfway on the accelerator.
ha ha, I get this sometimes, especially when I wear my boots.

I would start with cleaning the IAC, and see if that fixes it. You can get a can of cleaner at the parts store pretty cheap.

Here's the how-to incase you need it: How To: Clean IAC (Idle Air Control)
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  #7  
Old 01-28-2011, 06:12 AM
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Default Re: Fluctuating Low and Very High Idle

Thanks Mcpink. I still wonder how the IAC can pass enough air to cause such an extremely high idle. I thought it was only a ON-OFF sort of valve. Is it in fact variable sort of valve that can open a little bit if needed, or a lot of needed?
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  #8  
Old 01-28-2011, 08:54 AM
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Default Re: Fluctuating Low and Very High Idle

As I understand it, it's a variable sort of valve. It opens up a bit more when the engine is cold to raise the idle.
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  #9  
Old 01-31-2011, 02:40 PM
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Default Re: Fluctuating Low and Very High Idle

I forgot about tapping the IAC to see what happens, but I did remove it today (in -10degC). Doesn't look terribly carboned up. Piston moves back and forth, although not that easily, but smoothly. I'll clean it, put it back on, and try giving it a light whack to see if that helps (if it's still acting up).

Problem may have gotten worse. Sometimes engine won't startm if it's recently been running, but shut off for 20 or 30 minutes.

Holding it to the floor seems to help. I didn't think you could flood a fuel injected engine, but apparently you can....I can smell gas when this happens. Could be a different problem altogether. More testing once the IAC goes back on.
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  #10  
Old 01-31-2011, 03:20 PM
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Default Re: Fluctuating Low and Very High Idle

what engine??
Common mistake is people assume its IAC valve... when EGR failure is more common to cause this situation
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  #11  
Old 01-31-2011, 04:55 PM
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Default Re: Fluctuating Low and Very High Idle

2.3 litre engine. Both the EGR and PCV are next on my list. I have had EGR issues with other cars, but they always acted as a rough loping idle, not a long extremely high idle, then an almost so low it stalls idle, then a high idle (but not quite as high), etc., until it warms up and then seems fine.

But I appreciate the thought. If I get no-where, the EGR does seem like the next likely culprit. Maybe the IAC is working right and trying to compensate for a sticking EGR. sooner or later I'll figure it out.

Did I mention that this is a rather poor time of year to be working outside?....LOL.
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  #12  
Old 02-01-2011, 08:07 AM
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Default Re: Fluctuating Low and Very High Idle

This morning I cleaned the IAC and re-installed it. I guess I didn't have the electrical connector pushed on all the way, as when I started it, it idled low and I had to hold the gas pedal down a bit to keep from stalling. It was -8 degC outside.

Pulled the connector off and put it back on again and re-started the engine. The idle did go up over 3000 rpm, but didn't hang there like before. It kept coming down in 500 rpm decrements every 1 to 2 seconds and eventually stopped at a stable idle.

However the stable idle is now about 1500 rpm. Yet the engine sounds like it's actually about 750 rpm. It's almost like the tach is reading double.

Next I'll check the tach against the tach in my timing light.
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  #13  
Old 02-04-2011, 11:41 PM
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Default Re: Fluctuating Low and Very High Idle

Yes, that 500 RPM increment is the IAC doing it's 'steps' (I'm sure it's the same as a GM step motor IAC)

Possibly related problem: (2003 Bone Stock 2.3L)
I've been fighting a vacuum leak on the intake manifold itself at #1 cyl. I think I found it, so I'll cut to the chase without too much of the dramatics that I might normally include. There is a shaft sticking out near the base of the plastic manifold that had a serious leak. I think this shaft goes to the Intake Runner Control Valve (I think that's what it's called). You can't see it until you remove the P/S pump. Has anyone else had a similar issue, with a vacuum leak down toward the base of the intake manifold at #1? For that matter, if anyone's had theirs off, is there supposed to be some sort of sealed plug over that shaft, or is it sealed around the shaft - more internally? I ended up making a plug with aluminum the diameter was just a bit smaller than a penny, about .7". I sealed it on there with some B-half (Aviation Sealant). It didn't throw any more codes initially, and I'm waiting to hear back from the owner (hopefully early next week), as to whether it's good and fixed, or not. Anyone have a similar experience or have any idea what I'm talking about?

Thanks - Scott
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  #14  
Old 02-06-2011, 04:11 PM
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Default Re: Fluctuating Low and Very High Idle

No idea at all, although a pic might help.

Trying to picture what you are talking about, if you're plugging a hole (and I'm not sure why there is a hole), I'd make sure the plug has a flange or lip around it. You dont' want it falling inside and travelling down aroudn valves or inside a cylinder.

Seems to me there is a tube coming from there with a hose conencted to it. Can't remember what it's for. My truck isn't available for a while, so I might not be able to get back with any more info for a day or two.
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  #15  
Old 02-06-2011, 06:58 PM
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Default Re: Fluctuating Low and Very High Idle

I'm not sure I was clear enough:

I did talk to the owner today, he said that it is running much better, especially at stop signs/idle, which makes me believe that I was right about that needing to be plugged. You make a good point for anyone trying to plug anything on an intake. the plug I made was larger than the hole so it's not going anywhere, except falling off if the adhesive were to fail. I wish I could explain it better, but it really is hidden, I didn't find the problem and didn't even realize that the shaft (for the Intake Manifold Runner Control) was so low in the manifold until I removed the power steering pump and saw just the smallest portion of it sticking through this little hole (about .7" diameter). I hope this find helps someone, because it looks like a very weak spot in the design to me. Without having removed it, or seen one before, I'm convinced that there should be either a seal on the shaft, or a plug of some kind on the end of the shaft (or both), I'm thinking perhaps the latter (if nothing else, to keep it clean), and that they may tend to fall off leaving a nasty vacuum leak throwing a P0171, P0301, and a few others (as I am trying to recall off the top of my head, I think there was a P1295, but I can't swear to it). This also came about at the same time as the vacuum line broke down at the vacuum actuator that is low and near the firewall (I understand this is also a common leak, as the vacuum hose has a very tight bend right there to make it onto the actuator). If someone gets these symptoms, that might be another spot to hit with ether to check, right down close to the base of the intake manifold where it mates with the head, on the front side of the manifold at #1 cyl.
- Scott
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