2000 F150 4.6 Auto.

A little problem has been rearing its head from time to time. You see, every once in a while, when you touch the throttle she tries to die. Never quite dies......just wants to. More like a stumble really.

When does it do this? Usually very soon after the truck is started. Not when it is cold per-say, just after starting. Also, I have never noticed it happen when the A/C is on. See, I could run across town, run in the store for a sec, run right back out.....starts fine....still warm.....turn around.....touch the gas and bluh. It is NOT a repeatable problem, seems quite rare. Dang near killed me the other day. I was pulling on to a busy street and it stuttered in front of oncoming traffic. AHHHHH!!!! It seems as though once it recovers from the stutter, it clears up and everything is fine. It feels like she is asleep at the switch. "You want me to do what??? Uh-uh".

She has 99k miles. No code, new plugs, a clean K&N, clean oil, freshly serviced tranny, fuel system cleaner every 6k. All maintenance has always been by the book. Good power, great milage. All is good except for this little quirk.

Sticky/dirty IAC maybe????

 

Well, I cleaned the IAC (loads of crap in there), cleaned out the T/B (OMG!! You would not believe the gunk in there!! I used half a roll of shop towels on it!). I also cleaned the MAF (also dirty. a thin grey film over the wires) and cleared computer.

I started it up, let it idle 10 minutes, started the A/C and let it idle 5 more. Then took it out on the H-way for 10 miles.

It idles MUCH smoother! As far as the problem I was having goes......it didn't do it again. BUT it was a sporadic problem so we'll see.

BE SURE YOU USE INTAKE CLEANER!!! NOT CARB OR BRAKE CLEANER!!! The T/B and intake are coated with Teflon to resist carbon buildup (must not work worth a %$#@!) and most cleaners will remove this coating. Be sure to get "Intake Cleaner for Fuel Injected Vehicles". Says "Safe For Teflon" on the back. I bought the CRC stuff for like 2.99/can. Used 3.

 

The offical term used is tip in hesitation. If it comes back take a good look at your throttle position sensor. Sometimes they get a dead spot where the throttle first opens. Very easy to check with a DVOM. Key on engine off, get reference voltage then slowly open the throttle and watch for a smooth increase in voltage . A bad sensor will start out at say .4V and then drop off to 0 and back to .8 or so. I have seen the more frugal minded adjust thier TPS past the dead spot if it is right at the first little bit. Then they recal. the computer to get it used to the dif. voltage and there you go. ( its also not too expensive and very easy to change out)

 

I did test the TPS, got .98 closed and 4.58 WOT. I didn't really check it for smoothness but I'll have a look at that tomorrow. Thanx!