The 5.0 stings me again. I have an idle problem. I first noticed it a few days ago when I pulled up at a gas station after 2 hours of faultless highway driving. The motor was hunting badly with a rev swing of roughly 500 rpm from memory - perhaps more. It stalled a few times too. There were no problems with the car at all prior to this trip.
Upon further diagnosis it seems that it can take anywhere between 0 and 3 minutes or so after starting for the problem to become evident.
I've replaced the IAC motor and housing and have cleaned and replaced the EGR valve and verified that it opens and closes by applying external vacuum to it. Unplugging the IAC seemed to improve things slightly during the 1st day of diagnosis but now it makes very little difference to the idle. I've cleaned the PCV valve and can hear it clearly rattle. No noticeable difference can be detected when the engine is run with the oil filler cap off.
I've cleaned the battery earth. I've verified that all the leads are firing using a test lamp at the spark plug end but the car seemed to run smooth(er) when each cylinder was tested. Perhaps the fault wasn't evident when these tests were done as I performed them cold and only ran the motor for a few seconds each time observing that the lamp was firing. I've cleaned and roughly checked the gaps on each spark plug. I've also cleaned the dizzy and rotor arm. Lower TPS has a dynamic range of 0.75Vish - 4.2Vish and the upper TPS has a dynamic range of 0.8Vish - 4Vish. Swapping the TPS plugs over makes no difference.
The hunting is like a lumpy cam... quite periodic actually with a frequency of about 2 "surges" per second. It even hunts / surges at slow driving speeds. The fault is not constant. I can pull up at a set of lights and it will sometimes idle well, sometimes a little rough but mostly quite poorly.
There are no new
KOEO codes (I still get the MAF and EGR codes I've had for some time) and I can't seem to extract slow KOER codes, only the fast codes so I need a reader. I don't know why this is. I discuss my inability to extract KOER codes and the two KOEO codes in this thread.
Weird observation during EEC-V code extraction
Any ideas? Temp sensor?