I replaced my IAC a couple of months ago because the V8 would idle really low and not want to run. Replacing the IAC fixed that problem at that time. Starting a week or two ago, when I start the motor, it idles very high, upwards of 2000 RPM and slowly eases back to around 1000-1100 RPM. Am I losing the IAC again? If not, what else could cause this. I am new to this board and am very impressed with not only the content but the knowledgable folks here. Thanks in advance for any help.
Tejano
1999 F250 SD Ext. Cab, 8' bed, 5.4L V8, etc.
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2006 F-250 SD Lariat 4X4, 6.0 Liter, all stock
WELCOME to TDS.com [img]/ubbthreads/images/graemlins/biggrin.gif[/img]!!!! We're always looking for more gassers to help even things up (like that'll ever happen! Nobody's as ate up as these diesel folks... [img]/ubbthreads/images/graemlins/rolleyes.gif[/img]).
My experience is that when the IAC goes, it just won't idle on its own. I've not heard of it racing the engine, although I guess it's possible. Another thing to look at is your mass airflow sensor. If these get really dirty (usually an aftermarket air intake that's over-oiled) I've read where they've caused surges. Of course it could be dozens of other issues, so I've probably not answered the question... [img]/ubbthreads/images/graemlins/shrug.gif[/img]
Tejano, WELCOME! If I were you, on the principal of the idle problem alone, go back to where you had the Idle Air Control valve replaced and have them check it. Probably is unrelated (as previously stated, they (the engines) usually die versus racing. This will at least likely get you a discount on the diagnosis/repair, but better yet develope a relationship with your mechanic. Been in the business, repeat customers get better service almost always. He knows the truck, you, service habits, etc. FWIW, racing is usually a rich condition (bad fuel pressure regulator, stuck injector, etc). If you have done any work on the truck lately, make sure you didn't bump loose a vacuum hose (leak) the computer is trying to compensate for. Also, see if turning off (making sure it is off) the A/C or blower (defroster runs A/C compressor) makes a difference. Idle speeds are always increased by the computer to run the extra pump. HTH
Thanks for the comments. I haven't done any work to it lately at all. I have a good mechanic who knows me and i'll probably take it to him tomorrow and let him check it out. The racing happens whether or not the blower/heater/AC is on or not so I don't think that is affecting the condition. I'll probably pop the hood tonight and see if I can find any loose vacuum hoses or anything obvious anyway.
On a much more positive note, I finally got sick of that useless cup "holder" and went to my dealer and bought the new style cup HOLDER. Man, this thing is much better, it actually does what it is supposed to do. I got the idea and also the Ford part number from doing a search on this forum. This place is great although it is probably going to cost me money from all the great ideas I will get here. Anyway thanks again for the comments.
Tejano...OUT
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2006 F-250 SD Lariat 4X4, 6.0 Liter, all stock
You sure it's not the cooler temps? When it's cold out, the computer will richen the mixture and increase idle speed. Just like the old days with a choke on a carb. My truck does this. Settles right down within a minute.
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2005 V10, AT, Fx4 Dark Stone Metalic, Crewcab F350, 4.10LS, shortbed, towcomand, Extang tonno **SOLD**
I paid about $42 + tax at my dealer. Four 7mm hex head screws and about 10 minutes to replace it. Well worth it in my opinion. And the new cupholder has a little ashtray between the two holders. A good place for pocket change or whatever.
V10,
It could be the colder weather but I'm about 30 miles west of Houston and it's been upwards of 70 degrees the last couple of days and the motor still does it at those temps. so I don't think that is the situation. Seems like it does the same thing regardless of the ambient temperature. I had planned on taking it in to my mechanic this past weekend...just didn't get a round tuit.
Tejano
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2006 F-250 SD Lariat 4X4, 6.0 Liter, all stock
Well I guess it finally happened. I knew it would. LOL. Ford finally built the first self-repairing engine in history! And I own it! [img]/ubbthreads/images/graemlins/grin.gif[/img]
Man, I wish I knew what was causing that racing condition on start-up 'cause it stopped doing it. It was happening right up to the weekend before last and I towed the boat down to the coast for the weekend and back on Sunday. After that, the engine starts up and idles just like it is supposed to. Is it possible that there was some crud build-up on something or some sensor and the extra stress of pulling the boat knocked it off? Any ideas out there?
Oh yeah, happy new year to everyone. Let's have a great 2003!
Tejano <font color="red"> </font color>
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2006 F-250 SD Lariat 4X4, 6.0 Liter, all stock
I think I have one of those too!! Mine was getting worse and worse. The last week it did it every cold start. So I went out and bought an IAC. It did it for about 2 more days after I bought the new one (but never installed it) then it just stopped! We've had some cool to cold weather in Houston and it's been in some colder weather at our place in east Texas. Nothing for the past 2-3 weeks. The IAC is sitting on the my work bench. [img]/ubbthreads/images/graemlins/shrug.gif[/img]
Year or so ago we all had a similar discussion.... my new v10 was doing it the first winter (centeral Texas not very cold) and it just quit doing it. I think we all finally agreed that under some conditions the oxegon sensor, IAC, computer, Mass air sensor, all get confused. I really think it is a combination condition of two or more of the previous items causing the computer to command higher rpm.
I got in the habit of resting my foot on the gas pedal before a start. On one occasion that the engine went to high idle, I swear the pedal depressed..... the only thing that can cause that is acommand to the cruise control....very curious. Never does it when it is HOT out.
This winter my 27000 mile engine has done the high idle dance three times. But mostly on the mild mornings never on the really cold ones.
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White 05 F350 King Ranch 3 valve V10 5R110 Auto 4.30:1LS 4x4 LWB SRW born on 3 Sept 04
Yep, sure enough it started again about a week ago. I took it in to the shop Saturday and my mechanic looked it over. He said the IAC was operating to specs, the computer didn't have any codes stored in it, and he said he couldn't get the motor to race on startup at all while he had it. It did race (1700-1900 RPM) when I started it up to drive to the shop (3/4 mile) and it did it again when I picked it up to drive home.
Maybe it is a coincidence or not, I just find it strange that it stopped for a while after towing the boat (~3000 lb.) and then started again. Man, if the computer is "confused" I wish there was some way to explain to it what it should be doing. Also, since it started racing again recently, I noticed that when I am at highway speed and have to take my foot of the pedal (coasting down), the motor seems to drop 100 to 200 RPM just for a few seconds then comes back up. I don't know if this is related or not. Any ideas out there?
Tejano
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2006 F-250 SD Lariat 4X4, 6.0 Liter, all stock
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