Ok, a little back story:
It's a 2003 XLT w/ 4.6 & 124k on it.
I had a rough, surging idle to the point of stall on a few occasions. Truck ran fine while moving. I checked all the hoses, didn't find any leaks, and came to the IAC. Replaced it with one from CarQuest. Surging Idle went away. Great! But...
As soon as started the truck after replacing the IAC, I noticed that the truck would idle around 1100 RPMs for roughly 30 seconds to a minute, then drop down to the normal 650-700 RPMs. Also at this time, there was a loud "humming" sound. It was definately air rushing through something, or something like that. I had read another user talk about a humming sound after IAC replacement, so I wasn't alarmed by this, thinking it would go away.
Problem is, neither the high idle or the humming have gone away. What happens now is when you start the truck, it sits at 1100 RPMs for half a minute or so, has some very slight surging, then drops down to 650ish and holds steady.
When you start to drive, everything seems fine. When driving through the city at around 35-40mph, the RPMs stay up around 1100-1200rpms and actually hold you at that speed...I don't slow down at all.
When I go to stop at a light, the truck, actually pushes me and I have to use a lot of pressure on the brake pedal to stop. Then, just as I'm about to come to a complete stop, the RPMs drop down to normal and I lurch to a stop because of the pressure I'm having to put on my brake pedal.
In addition to all this, the loud humming continues and is becoming more prevalent. Only happens at idle or while coasting. I can get it to go away when I step on the gas. If I tap the gas, it goes away. Sometimes it stays away, sometimes it comes right back.
So...now I'm trying to figure out what the heck is going on with the truck.
I did not disconnect the battery, but I've driven almost 2000 miles. I would think the computer would have re-learned by now.
Could it be the TPS?
Any help would be greatly appreciated. Thanks so much.
It's a 2003 XLT w/ 4.6 & 124k on it.
I had a rough, surging idle to the point of stall on a few occasions. Truck ran fine while moving. I checked all the hoses, didn't find any leaks, and came to the IAC. Replaced it with one from CarQuest. Surging Idle went away. Great! But...
As soon as started the truck after replacing the IAC, I noticed that the truck would idle around 1100 RPMs for roughly 30 seconds to a minute, then drop down to the normal 650-700 RPMs. Also at this time, there was a loud "humming" sound. It was definately air rushing through something, or something like that. I had read another user talk about a humming sound after IAC replacement, so I wasn't alarmed by this, thinking it would go away.
Problem is, neither the high idle or the humming have gone away. What happens now is when you start the truck, it sits at 1100 RPMs for half a minute or so, has some very slight surging, then drops down to 650ish and holds steady.
When you start to drive, everything seems fine. When driving through the city at around 35-40mph, the RPMs stay up around 1100-1200rpms and actually hold you at that speed...I don't slow down at all.
When I go to stop at a light, the truck, actually pushes me and I have to use a lot of pressure on the brake pedal to stop. Then, just as I'm about to come to a complete stop, the RPMs drop down to normal and I lurch to a stop because of the pressure I'm having to put on my brake pedal.
In addition to all this, the loud humming continues and is becoming more prevalent. Only happens at idle or while coasting. I can get it to go away when I step on the gas. If I tap the gas, it goes away. Sometimes it stays away, sometimes it comes right back.
So...now I'm trying to figure out what the heck is going on with the truck.
I did not disconnect the battery, but I've driven almost 2000 miles. I would think the computer would have re-learned by now.
Could it be the TPS?
Any help would be greatly appreciated. Thanks so much.
