My truck keeps on dying whenever i slow down. I'll drive fine down the road, no problems, when i slow down and come close to a stop it dies. I can put it in park and start it up again no problem. When I put it in gear it idles at about 400-500 RPM's. That seems a little low to me, is it? It will idle without dying but when I come to a stop it dies. The battery is obviously fine because it starts up everytime. At first I was thinking it was the torque converter, but it's not like it's still trying to push foward, it just dies? Any ideas or suggestions greatly appreciated. Thanks. It is a '97 F150, 4.6L, V8.

 

It certainly could be one of many things. Could be the fuel filter or air filter among other things. Have those been changed out recently? That would be an easy place to start.

Hunt4Fun

 

I haven't changed the fuel filter lately. But if it was the fuel filter, would it still drive fine down the road? I just put an intake on it about two months ago so I don't think that is it. Maybe though, I will clean it today. Thanks for the suggestions.

 

Sounds like you need to clean or replace your Idle Air Control Valve (IAC). Takes about 30 minutes to accomplish this task.

 

I had a problem with my '77 F150 (400 engine). I would be driving and my truck would die at full speed. I would restart during deceleration which was interesting on a freeway. Turned out problem was electrical and replacing the square black box (coil, or electronic..can't remember). Just in case the obvious fuel flow fixes don't work.

 

Yankee, how do I replace the Idle Air Control Valve. Is there a website or forum that will tell me how to do it? Thank you very much.

 

https://www.f150online.com/forums/sh...+control+clean
https://www.f150online.com/forums/sh...ight=iac+clean
https://www.f150online.com/forums/sh...ight=iac+clean
Search for more info.

 

well i pulled the IAC off and cleaned it with brake cleaner a couple of times and it still didn't look that great to me, my truck does have 160 thousand miles on it, so i went ahed and replaced it and it fixed the problem and I have noticed that my truck idles better. Especially on start up, the RPMs used to shoot up to about 2500 to almost 3000 and now it starts clean without the high rpms. Thanks for all your help guys, it is greatly appreciated. And it saved me a hell of a lot of money. Thanks.

 

Glad it got `r` fixed!

 

Bad news, it died again today on the way to work so i finally took it to my mechanic and he hooked it up to his machines. The barometer in the mass air sensor has gone out and it is reading like i'm 3 thousand feet higher then i really am so the engine is getting the wrong mixture of fuel and it idles all screwed up. Not to mention killing horsepower and gas mileage. A new mass air sensor is only $110 bucks and two little bolts. Still not a very big deal. Thanks again for all your help, and the IAC probably needed to be replaced because it was VERY dirty and it does idle and start better then it did before. So we'll see.

 

Glad to help.

 

I would like to add add that the upper intake plenum ports can get clogged up on the 4.6L engines.

http://www.fordf150.net/howto/throttlebodyclean.php

 

I was having the same problem. I called the dealer and they wanted 250 to replace it. I just want to says thanks to all. I took the IAC off and cleaned in and put it back on. It took about an hour. The truck has been running great again for a week now. thanks for the help on the web site.

 

I put a new mass air flow sensor on today and it still died. I checked the upper intake ports and they are clear and suckin air like they should. I don't know what to do. It ran fine all day untill I put the new air flow sensor on it. The reason i even changed it was because the barometric pressure was still to low on the old one. What do I do know, any other suggestions? Thanks? Also if I clean the IAC what do I clean it with. Its brake cleaner all right?

 

You probably need to make sure you reset the computer. It may still be trying to adjust using the old PCM's bad readings.

Disconnect the negative battery cable and switch your headlights to on.

Let it sit for about 30 minutes. Then put it all back and start the truck. Just let it idle for about 10 minutes, and dont run any accessories (radio, AC, etc).

To clean the IAC I used intake cleaner, you're not supposed to use brake cleaner on our intakes because they have special coatings and brake cleaner eats that away, or something like that.