It's not a Bronco, but it bucks like one...

[Joe_theboob]

Here's a new issue, My 2001 LS V8 suddenly started "bucking" at full throttle. I'm thinking it's a fuel issue cause it seems like it's losing all power/torque just fow a 1/2 second or so - the whole vehicle lurches as it makes power then dies then back to power. It's not a single cylinder miss-firing... The car has 85k miles and the orig fuel filter and pump.

This only happens when your foot is on the floor. Any other driving condition or throttle position and it runs great.

Any ideas / thoughts are appreciated. Recent changes are; New Spark Plugs (Autolite Platinum), 1 new coil, replaced K&N with factory airbox (cause now it's winter).

[shorod]

Don't rule out a cylinder misfire, from your description, it could still be a cylinder misfire.

Find a fuel pressure guage and measure the fuel rail pressure. What reading do you get? Next, you are certainly due for a fuel filter, change it. Even if it doesn't fix your problem you are overdue. Measure the fuel pressure again.

Also check the Mass Air Flow (MAF) sensor for contamination from the K&N filter oil.

If you can locate a friend with a scan tool that has the datastream capability, monitor the cylinder misfires when the car acts up, as well as the oxygen sensor voltages and the fuel pressure. If you can find a professional scan tool that can plot these and record for long durations, even better.

-Rod

[Quik_LS]

+1 - likely a mis-fire.

[Joe_theboob]

Thanks, any idea where the fuel filter is? Is it in the engine compartment, under the car or in the tank?

Also, I'll run the codes and see whats there if anything, there is no check engine light on.

If it ends up being a mis-fire I'm just gonna replace all the pos coils...

[shorod]

If you determine it is a misfire, review some of the many posts on this forum regarding the coils and what often causes them to fail. Be prepared to replace the valve cover gaskets prior to installing new coils.

-Rod

[Quik_LS]

fuel filter is in the driver's wheel well - pull back the plastic liner on the inside of the wheel well - firewall side. It's held in with a bolt and two standard r-clips.