spade4823

2002 f150 4.2 v6. the idle goes up and down when idling at stop lights and when clutch is disengaged.i replaced the iac and maf sensor but still idle up and down at about 200 rpms to 1500 rpms, any help or ideas also no check engine light is on

bradseabridge

I wanna say TPS

02 supercrew

I've got the same issue mine only drops to around 400rpm's then up to 800 or so only does it in gear at a stop when a/c compressor kicks in...

Flacotaco121

Same problem here , did you guys found the problem ?

ford mann

check your vac. lines make sure there is no cracks or pin holes or anything to make them lose vac. pressure when i did my build i had the same problem it would gallop when it was in gear and sometimes even stall out, got all new vac. lines and runs like a champ.

Sledhead24-7

Mine does the same thing

Flacotaco121

Do you have the diagram .?

ford mann

no i dont have one sorry, i just went through and found all of them especially the one on the back of the throttle body that one seems to be the most problem for some reason.

03f15012

Mine did it once a few months ago. It has never done it since, and I have the same motor you do. a 2003 4.2

Dholla

Are you referring to the gas/fuel abg hose that goes to the vapor management system? If i remember correctly, it connects to the back of the throttle body, or it may be the intake. Can't remember exactly. But this one gave me trouble