i have a 5.4 2001 it jerks on acceleration and misses at full throttle. when i let off throttle and let slow down after a few seconds it drastically slows it acts like there is an engine break on it. i have tried new packs, fuel regulator, oem plugs, fuel filter, air filter and maf sensor. will a vacuum leak make it do that i have put my finger over the hole on the vmv and my understanding is that is supposed to kill the motor but it does not and i can hear sucking air. oh and there is no codes or even soft codes have had it checked with dealer computer. any help would be great.

 

I had the same problem last week but I had a CEL (#2 cyl misfire). Swapped the COP and plug but still the same thing. I pulled the fuel rack and cleaned up/blew out the #2 injector. Runs fine now.

But...since you said you can hear air, I'd first check the PCV elbow towards the back of the plenum by the pax firewall. It's a PITA to get at but they have a tendency to rot out over time.

 

ok i will try it thanks.