Would be interested to hear from the mods or interested gearheads why it is often suggested that a dirty fuel filter may be responsible for the shudder from 45-53 mph (prox) but there may be no noticeable decline in WOT performance?

Is it because the engine is lugging along near a peak torque condition at 45-53 MPH with the torque converter locked, and consequently is using a high rate of fuel? Hard to believe that would be more fuel used in a standing start, WOT condition.

Electric fuel pump should have fairly constant flow rate available at the injector rail, regardless of throttle position.

Thoughts, guys?

I'm racking my brain and don't know why...but...

It must be related to why your engine misses under those conditions as well.

While a Stink'n Rot'n Dirty Fuel Filter could possibly cause drivabliilty issues, I doubt it would be the cause of the infamous shudder between 45 & 53 mph. The ignition wires would be the first thing I would suspect if they haven't been replaced in awhile.

"Is it because the engine is lugging along near a peak torque condition at 45-53 MPH with the torque converter locked, and consequently is using a high rate of fuel? Hard to believe that would be more fuel used in a standing start, WOT condition."

No, it'* not. Fuel demand is a function of RPM. the fuel pump in our cars is obviously designed to handle WOT conditions at full pressure (3 bar). The only thing different happening at low RPM is that more fuel is returning to the tank via the return line.

Ergo, any lesser demand than WOT is not going to cause problems. If problems are caused by a diry fuel filter, they'll occur at any RPM or throttle position.

As an old-timer myself, I've had to learn to rethink fuel supply vs. RPM as provided by our old mechanical pump, single-line fuel systems.

"It must be related to why your engine misses under those conditions as well."

Correlation is not necessarily causation.

No doubt, but something to think about none the less.

I would never attribute those symptoms to be fuel delivery. It'* ignition related 90% of the time. The rest of the time it'* a trans problem. Rarely fueling.

I tend to agree, probably why I posed the question. Elsewhere in the forum, dirty filter is proposed to be a cause of shudder, but nowhere has that been necessarily discounted.

Until now.

I also agree that a dirty filter should show up as driveability across all rpm and driving conditions.

Everyone is an expert on a bulletin board, ya know!

Although the typical signs of a clogged filter would be a lack of fuel delivery at higher rpms.

We've been religiously preaching ignition for these symptoms for over 2 years on this forum. It'* typical for the 3800.