I am getting the P0402 code on my 2002 Ford F150. Yes it sputters sometimes at low speed. I changed the EGR and cleaned out all of that crap that throttle body. It worked for about 3000 miles and now it's back on and sputtering again. Vacuum leak? is that hard to get to? Is that gasket hard to get to. Becuase I too don't want to crap open the piggy bank. Please advise
i have a 97 f150 4.6 doing the same sort of thing. p0402, stumbly/shaky engine performance. i have worked through most of the same fixes: clean throttle body, replace most of the egr parts, plugs, wires, etc.... i'm thinking of replacing the vacuum hoses throughout. still not sure if this is going to solve anything, does this code pop up from maf or o2 sensors? this sort of thing seems way too common for there to be so many gremlins to hunt down in these engines.....
Sputtering and surging at low speeds sounds like a vacuum leak. Check the entire PCV circuit. The rubber elbow on the intake is the usual suspect, but the rubber connector on the PCV valve end deteriorates and causes problems, too.
Make sure the new DPFE you put on there was a genuine Ford/Motorcraft part and clean the carbon deposits from behind the throttle plate.
Will a leaking IAC valve throw a 0401/0402 code? I know a bad one will cause idle issues, but I never heard of it causing a code. That's a new one.
When a IAC fails it usually fails shut causing the engine to stall at idle. That's the opposite of a leak. What would cause excessive flow whether real or perceived. If the EGR valve is sticking open when not being commanded to open. Or is the DPFE could erroneously report that the EGR is flowing when it is not.
I've replaced IAC's before and they had problems on idle. Some wouldn't. My 01 F150 with the 4.6-v6 has had the DPFE replaced twice in 131.8k. The truck never missed a beat. Run like a new one. Just turned on the light. Didn't even effect my milage.
I don't remember the code number, but recently went thru a leaking upper intake manifold gasket. Turned on the "Check Engine" light, and went from atleast 400 miles on a tank of fuel, to 325 a tank. Yes it's been fixed.