Lotsa gray carbon in the plentum area Thomas. I've been told that IAC motor valve can fluctuate rapidly when running like a buzzing sound. Don't go spend the $ yet for a new IAC. Now I going to go pull the IAC on my mother-in-law's 4.6 Crown Vic and watch just how much movement it has tomorrow morning. Emission System - Idle Air Control Motor Testing & Replacing - 1 of 2 - YouTube
What about the other parameters mentioned in the video? Cold start high idle then to low idle? AC on or hard steering input changes idle? Resistance check terminals with an ohm meter? Think I may have said it backwards on the 10,000 ohm check. I wish I could say definitely it was the problem but those IAC ain't cheap on a 4.6 an your about out of options on the process of elimination.
Like I've said before, it runs absolutely perfect except for this starting issue. I personally think its an ignition problem. I have no codes but Im still leaning towards ignition problems.
and its still doing it...hmm.... mine went out last yr. it would start but die immediatly. I could start it and hold the gas pedal and it would rev and I could put it in gear (bad idea when your revving it to keep it running cuz it will not like it) and go it to drive...but if you let off the gas it would die, had to limp it to the shop. my work truck (5.4) did that too this past summer, new IAC and we were back in business. now why yours and Laurens will crank and start after a while and only do it sometimes I do not know. I may have my shop look at it when she gets back in town.
what about a spark tester so you can check to see if it is firing during the suspected ignition problem? I had an uncle who wasn't afraid of 20K volts to hand check 'em back in the 1970's.
Yea, I'm not checking spark with my hand...haha I don't have a spark tester. Use to have one, but the so called person I loaned it to can't seem to find it....
