Our Community is 940,000 Strong. Join Us.


2000 Explorer changed IAC now have loping idle & hum


greybeard23
02-02-2012, 06:14 PM
I just changed an IAC that was acting up, rough starts in cold weather. Now I have a loud hum in the 4 inch intake and for a minute it idles at 2000 then drops to 500 and lopes, almost stalling.
Three years ago I had intake gaskets done and a new kit of some kind for the cam.
New fuel filter, wires, plugs, coil, air filter.
Any ideas?

No CEL, took it for about a 20 mile ride to see if the computer needed to reset, didn't help. Didn't do this before I changed the IAC, but I would have to tap it once in a while to get it to idle, thats why I changed it.

shorod
02-02-2012, 10:39 PM
Welcome to the forum!

Did you clean the passages for the IAC and the throttle plate before installing the new IAC? If carboned up passages is not the issue, I'd be looking for a vacuum leak. I'd actually connect the scan tool and monitor the fuel trims as well as have the scan tool control the IAC to attempt to achieve set engine speeds, testing the function of the IAC system.

-Rod

greybeard23
02-02-2012, 11:11 PM
Hello, and thanks for the welcome.
I did clean everything before I installed the new IAC.

I looked long and hard for any leaks. I did not test for any. But could not find any.
I do not have a scan tool to run diagnostics or access to one at the moment.
The old one seemed to give me problems mainly in cold weather, but not steady. I could tap on it and sometimes that would straighten it out and it would work for awhile.

I may in the morning clean up the old one as best as I can and reinstall and see if I still have the same problem, if so I will know thats not it and I must have done something I didn't see while installing it

joemffields
02-02-2012, 11:58 PM
I had the same problem with the high rev to 2000 and then would drop to 500 and keep doing that for awhile then i would shut it off. I had just got done changing the IAC, MAF, air filter, plugs and wires just a couple of weeks ago, so i know that was all good this time. Anyway there is an o-ring that you can't get at autozone, o'reilly's, advance, ect., you have to get it from a ford dealership, it's called an EGR Connecting Tube Seal, part number 9J469, that mine had just worn out, causing it to get more air then it though it was getting, and the IAC can't adjust because its right below the IAC and doesn't know that it's getting that extra air. Got that fixed with some silicone gasket maker. It started doing the same again, so i checked the ignition coil sure enough it was off by just enough to make it not run right. A trip to o'reilly's, $69.99 for a new ignition coil, 10 minutes under the hood, and she runs like nothing was ever wrong. hope this help.:smile:
P.S. Get a Haynes Manual, $14.99 o'reilly's

greybeard23
02-03-2012, 12:09 AM
I changed the ignition coil, plugs and wires yesterday, then went into town, about 45 miles round trip and picked up the IAC this afternoon and installed it, thats when the problem started.

Haven't done anything with the EGR, I have had a Haynes Manual since I bought the car eleven years ago. Guess I need to invest in some diagnostic tools.

Just has me stumped because it didn't do this until I intalled the new IAC.
I am also getting this loud hum, which varies with the RPM, sounds like its coming from the four inch air intake.

Also, new air filter, cleaned the MAF sensor, although it sure didn't look like it needed cleaning.

shorod
02-03-2012, 07:59 AM
The loud hum from the intake sounds like something I remember reading here, but I don't recall what it was. I do recall some folks referring to a hum from the intake area being caused by the IAC, but I don't think those changed with engine speed.

Your idea of cleaning and reinstalling the old IAC is a pretty good one to attempt to rule that out. You might even consider not cleaning it to theoretically remove that variable.

Another test to see if the IAC is functioning would be to turn the steering wheel all the way to one of the locks and hold it there for no more than a couple of seconds. If the engine speed drops significantly or even stalls, then your IAC is not doing its job. Same with the A/C - if it's warm enough that your A/C compressor clutch will engage, turn on the A/C or defrost and see if the engine speed drops when the clutch engages. If so, the IAC isn't working properly.

-Rod

greybeard23
02-03-2012, 11:37 AM
OK, so I have removed the new IAC and installed the old without cleaning it. Won't idle unless I hold the throttle. Hum is gone!
I shut the car off, tapped on the old IAC, restarted the car and it is idling normally.
I am now on my way to return this part. Cost me 99.00 with discount and tax.
The only difference I can see between the two, other than the shinyness, is the pintel or disc on the new one is at least 3/16 from being closed when disconnected. On the old one that disc is closed tight.
I have now cleaned the old one and reinstalled, still had to tap it to get a steady 6 -7 hundred rpm.
Thanks for all your help. Someday I will invest in some diagnostic equipment, probably need a new ride first though. :jerking:

joemffields
02-03-2012, 12:58 PM
i also noticed that 3/16 of a gap on my new one, it was on the old one as well. so i think that gap might need to be their, it is a solenoid so it can open more as well as close more depending on the voltage going to it, so i don't think that was the issue. i would definately get a scan tool on it to make sure you don't have a problem though. good luck, hope everything works out for you.:smile:

greybeard23
02-03-2012, 01:42 PM
i also noticed that 3/16 of a gap on my new one, it was on the old one as well. so i think that gap might need to be their, it is a solenoid so it can open more as well as close more depending on the voltage going to it, so i don't think that was the issue. i would definately get a scan tool on it to make sure you don't have a problem though. good luck, hope everything works out for you.:smile:

When I returned the new one this morning, the gentlemen at the parts store said on some vehicles like GM, that you have to drive them about four miles to get that gap to close. Well, I drove a good thirty miles, both with my foot off the throttle just idling along at 10 or 15 miles an hour and at 60 and 65, just to try and get the computer to maybe reset.

Will have another new one by this evening, will install it right there at the parts store and see how it goes. Ran the old one into town, round trip about 45 miles, and it is idling fine, both at stop lights and back here. Although I did have to tap on it to wake it up when I first put it back on this morning.

But I do need some good scan tools. I am not at home, I am tent camping and have been since last May. Been traveling all around the states, carry enough tools to do most of my own work. Traveling in a 12 yr. old car with 130,000 miles you have to expect to do some work once in awhile.

shorod
02-03-2012, 02:25 PM
If your tent camping brings you near Cedar Rapids, Iowa, look me up. I will connect the professional scan tool up and we can see if anything stands out.

-Rod

greybeard23
02-03-2012, 02:48 PM
If your tent camping brings you near Cedar Rapids, Iowa, look me up. I will connect the professional scan tool up and we can see if anything stands out.

-Rod
Well, come March I'm heading into Georgia for some gold panning, then into N.C. By May I will be in N.H. for a bit to restock for summer, then I am headed to the Dakota's for a bit, so I just might be going through Iowa.

Right now she is running better than she has for awhile, but that is just by feel and hearing. No telling what might really be going on inside.
Thanks, I sure appreciate the kind offer.
These new cars sure aren't as easy to fix without the proper diagnostics, sure like the cars I had when I was young, my 59 ford, 60 Volvo, and my 77 suburban. At least those vehicles you could work on.

greybeard23
02-03-2012, 05:31 PM
Sometimes you just have to sleep on a problem to come up with a plan to acquire the solution.

I just returned from picking up my second new IAC. Installed it on location and the old girl purrs like never before.
The opening between the pintel and the seat on this one was only about 1/16, about 1/3rd what the other new one had that gave me erratic idle and the hum.

Thanks all, for all your ideas and willingness to assist.

Great Forum, will be checking back often to check on new ideas and pending problems.

shorod
02-03-2012, 09:59 PM
Great, glad to hear you got it fixed! Thank you also for following up on your thread.

-Rod

joemffields
02-04-2012, 03:52 AM
by chance, when you put the new one on did you unplug the battery so that it could erase the old sensor and learn the new one.

greybeard23
02-04-2012, 07:50 AM
by chance, when you put the new one on did you unplug the battery so that it could erase the old sensor and learn the new one.
Yes I did disconnect the battery. Guess I have gotten into the habit of doing that almost for any thing I do on this vehicle. I think my Haynes Manual has gotten that drummed into me.

Add your comment to this topic!