Have approx 2,800 miles on my 2001 F-150 (4.6) Auto. Every morning, upon initial start up, throw her in reverse back out of the driveway, into drive and hit the accelerator....delayed throttle response (stumble). No backfire or poping she just takes her sweet time about wanting to accelrate (about a 2 to 4 second delay). After the inital stumble (or two)...she won't do it the rest of the day no matter how many time she's shut down and re-started. Any ideas of what the problem may be? Took off all the coil packs from the spark plugs thie weekend and coated the boots with di-electric grease. Still the problem exsists??? Help

No mods on the truck...yet.

JR

 

Not sure about the 4.6 truck motor setup, but on Mustangs I’d guess it was fuel system related. Particularly as it has to sit for a while (over night).

Just for kicks try leaving it in key-on position a little longer and see if the pump will prime the fuel rail fully. My guess is that the line is not holding enough fuel (or fuel pressure) until after you've run it for a bit.

Could be a bad pump or more likely a small air leak in the system

-m

 

Thanks Bitten...I'll give it a try tomorrow morning. Hesatation was really noticable this morning in wet/ humid conditions (69 degrees). Once she got up to operating temp we were fine.

JR

 

Sounds like it could be some sort of emissions related problem too. Maybe an 02 sensor,or EGR valve? If it's fine once it's warmed up,it could be something that's not working properly during the warmup,and either unsticks or is not used once you drive it for a while. I used to have a Ranger that ran REAL bad until it warmed up,and it turned out to be a bad thermostat and 02 sensor. Sometimes it would get extremely bad gas mileage and blow black smoke out the tailpipe. I also think I saw someone with the same trouble a few weeks back on the boards here. Something about the EGR system,but I can't be sure. Hope this helps a little,,,,,98

Get a code reader,they can tell you what's going on

 

Screamer...thanks I'll keep that in mind when/ if this esclates to my Dealer Service Center. Folks on this board more capable on solving or diagnosis of problems than most Service Centers. I think I'll bring along yours and Bittens threads as back-up. Names changed to protect the innocent...of course.