im sorry i know this has been posted so many times but i cant seem to find the forum but anyways, for about a month now my truck has been acting funny at idle more specifically when i come to a stop the idle will drop down to 400 rpms raise to 700 and rest at 550 rpms fluidly. just the past day it decided to drop down to 100 rpms sit there for 2 seconds and then die. which it has done 3 times since. Ford says they cant do anything about it and have told me to wait untill something major happens. please help (a few more details but im sure i will be able to add them with advice from yall.)

 

Sounds like a bad IAC valve. There are a couple of pictures in my gallery here https://www.ford-trucks.com/user_gal...4&albumid=4956

 

ok so, i had the IAC replaced about a month ago due to a "horn" sound coming from the IAC and the instant i drove it out of the lot from ford it started this problem, so i take it back last week and they said its unrelated. they also replaced the egr valve and pcv i believe.

 

I have had many of the same problems: horn (replaced IAC) and dipping to 450 before recovering, although I have never had it go below 450 and just die. Do you have an intake kit or maybe try cleaning or replacing your MAS. Maybe you happened to get a deffective IAC.

 

my mods list is as following : Granatelli MAF, Volant Cold Air Intake, BBK 75mm Throttle Body, AIRraid TBS, Granatelli Coil Boots. and they deny giving me a faulty IAC which im not sure if they are legit because i live in a somewhat small town and they are not the most experienced (Appel Ford)

 

Maybe try putting your old one on if you still have it and see if it still does the dying thing. Ignore the horn and jsut forcus on the RPM problem and then report back.

 

ok ill try that, i wont be able too for a couple days but as soon as i get the time i will post the results

 

on a relative compression test it revealed that cylinders 5-8 (drivers side) are down between 5-8% replaced all 4 COP's and that fixed the idle problem for about 20 minutes. could the altenator cause an idle to drop?

Note: the faster i slow down say on the highway 60-0 the lower the idle goes down before it comes back up to rest.

The lights also dim pretty bad when i roll all my windows up at the same time, is that normal?

 

When you crank out more amps out of your battery/alternator by for example turning additional lights on, the engine should react by actually raising the idle for atleast a few seconds. It might drop for a brief second but should rebound quite quickly. That whole depression issue is a little out of my knowlege, so I don't know, sounds like your problem could be more than just the IAC. Good Luck

 

I just had my battery cables replaced because i thought that may be the problem, turns out that was only partially the problem. I was wondering if this truck (4.6l 2001 VIN W 470RW) is equipped with a speed/distance Sensor. I just read through a search in google that this could cause the symptoms that i am experiencing. Any response is greatly appreciated. btw this problem is driving me insane, stalled in the middle of a highway trying to cross...