New too the forum but have been here and to others trying to find answers. I have a 2002 E350 with the 5.4 motor. Had a miss so I replaced all of the plugs and coils. A few months later it went from having the miss to not wanting to start and stay running, lost power, to which I found that unplugging the MAF sensor would allow it to run better and stay running. Cleaned the MAF sensor a couple of times then had to replace it. Then it started having stalling issues. Never any check engine light. Then it wouldn’t start. Had it towed home, late at night, only to have it start right up the next day. Checked some Ford sights and decided to replace the IAC valve. Mine was missing a spring inside when I removed it. Put new one on and it still has issues. Now it will start when cold but once it warms up or I drive a while it won’t start, does turn over. I discovered that if I hold the pedal to the floor it will start but idle high or rough then stall when I put it in gear. I wanted to see if spraying cleaner through the throttle body would fix the idle issue but when I take apart the air intake, so that no air flows past the MAF sensor (it is still plugged in to the harness) it won’t start, cold or hot. As soon as I connect the hose so that air is drawn through the MAF sensor it will start with the above issues. So, what did I screw up when I replaced the parts or is there still something else wrong that needs replaced? Thank you for the help.

 

Please don't feel offended by what I am about to say.
A, lot, of times, the more parts replaced/touched , the more problems are sometimes created. When there was only one problem now we have several because some "new" parts can be questionable these days and some things go together other than right, plus, unknown to the installer , some connections get disturbed.

It can be quite frustrating guessing and expensive too.

I can't imagine an IAC operating well for a period of time then malfunctioning due to a missing spring, puzzling..

Usually if unmeasured air is getting past the MAF sensor the engine can run lean because the computer is adjusting injector on time according to the amount of air the MAF says is coming in. If the MAF is supplying incorrect info it can cause a rich condition, sometimes a throttle position sensor can give false info.
The better way to go after this is with a quality scan tool that can provide data stream info like fuel trim. You might consider a good shop to check this out.

 

hanky- it would take an awful lot to offend me. what you said makes sense the issue is that I was getting the check engine light prior to replacing parts. I don't just start replacing parts without plugging in the obdII. when it started stalling and having starting issues there were no check engine codes on my scanner and no check engine light. at first itt was just a random every once in a while issue that never threw a code. this is what was confusing to me. then it just wouldn't start. once i get the code i research it and check what others have done to fix the issue, since it is my understanding that one code can be caused by many different problems. it is also possible that the missing spring in the original iac fell out during removal, trying to get in and around the engine while squeezing past the front seats is not easy. anyways after a couple health issues being taken care of i finally got back to checking into this issue. upgraded my obdII to be able to get live info while it was running, plus being able to link it to my phone, and found the issue. obdII was showing temp at -40F on iat sensor and the coolant temp sensor. neither value changed while the engine ran. turned off tried to start and had to hold pedal to floor to get it running. temp values were still the same. i would have thought that this would have thrown a code but it did not. anyways long story short it was the sensor in the drivers side head. when i tried to unplug it the plastic broke/crumbled. anyone that has had to change this sensor knows what a pain it is to see let alone get your hand on it. new sensor, new pig tail harness from it to main harness and problem solved. hope this helps anyone else that has to deal with this type of starting issue.

 

It is always nice when we (you) solve the problem. Thank you for sharing the info with us.

As I recall , if we unplug a temp sensor if it goes to -40 that tells us the wiring is OK.Since you received the -40 reading that would tell us the sensor or the wiring had a problem.Now You hopefully will remember that little trick.
Thanks again for the update.