Faulty Air Flow Restriction Gauge?

[MojaveJoe]

Just bought this truck. Dealer installed a new air filter (the 4" deep pleated kind).
I have noticed that the Air Filter Restriction Gauge has been moving to half flow.
Reset it, then drive like an old lady and it stays at zero restriction.
Do 3000rpm in Park, and it stays at zero.
Today I reset it, then took it for a quick test ride.
WOT twice in the first mile, 3000rpm twice. Pulled the gauge to half restriction.
Reset it continue my 20 mile trip never exceeding 2500, and gauge stayed zero'd.

Obviously without a load on the engine the air flows freely enough.
But use the pedal to step the transmission down one gear and accelerate hard, (over 2500) and restriction begins.

Wondering what might cause this? and if it needs attention?
I certainly can't complain about the performance when passing. Plenty of power compared to my '04 305HO.

One last observation. I removed and cleaned the air box which had some red oil in the bottom. Also the AFR Gauge had oil film around it inside the box and outside too.
Looked like K&N oil to me. Got me thinking the gauge my be fouled with oil, but can't understand how the oil even got to it?

Any ideas or suggestions?

 

[seafish]

If you have any progammer on your truck at all it will pull the "filter minder" down to half easily.

 

[MojaveJoe]

Nope. Well not that I know of, anyway. Pure stock as far as I know.

 

[mwilson]

Good to go. As long as it remains in the green don't give it a second thought. That also indicates that your air intake ducting is tight and performing as it should.

Go buy some fun stuff for your truck....

 

[Regcabguy]

I've got the PSM downtube and can't get the filterminder to budge.

 

[petersonj]

Obviously without a load on the engine the air flows freely enough.
But use the pedal to step the transmission down one gear and accelerate hard, (over 2500) and restriction begins.
Wondering what might cause this? and if it needs attention?

Good question. The air filter restriction gauge (filter minder) is a very useful tool, not only for determining when to change the air filter, but also for determining the condition of the air intake system between the air filter and the turbocharger inlet (as Mwilson pointed out). The air restriction gauge uses the weight of water (recorded in inches of height) as a means to express the pressure drop of moving air passing though a filter. Not that long ago these air filter restriction gauge came with numbered graduations - typically 0-25" of H2O, to show the maximum pressure drop from one side the air filter to the other while engine is operating.

Unfortunately, recently the numbers have been removed on many gauges, such as yours. On your gauge the green area would represent a restriction (pressure drop) from 0" to around 20" H2O, the red area would represent a restriction of about 20" H2O or higher (time to change the air filter). The gauge will always show the highest restriction that occurred since the last reset. In your case you are right in the middle (around 10" H2O) and you are fine, as other posts have noted.

The most informative test you can perform is with the engine under a load. Pick a higher gear in which you can reach engine rated RPM's under a wide-open throttle for about 2 or 3 seconds. This condition will allow the engine to produce near maximum power under full boost, thus generating maximum air flow through the air filter and intake system. Provided there are no leaks in the intake system, the recorded measurement will represent the condition of the air filter.

I have replaced the air filter restriction gauge in my truck with an analog air restriction gauge inside the cab. The benefit is that I can observe recordings under different driving conditions as they happen and get a better understanding of the variables that affect air moving through the air filter and intake system. Also, a change, such as a lower reading than normal under a specific engine load, would alert me to a possible leak in the air intake system. Using the analog gauge in the cab, I have observed that a new stock air filter in my truck records about 5" H2O under above-mentioned test conditions.

Hopefully, with all the TDR members help, you will breathe easier,

-John

 

[Ozymandias]

Mine sucks down close to Red even with a brand new filter, and stays there for the next 20000M until I change the filter.
I don't care about it.

 

[cerberusiam]

Put the 4" pleat filter in there and open the box up with hole sin the bottom or a cold air tube. Even with a programmer it won't pull down until the filter gets dirty. The less restriction it has the better air you are going to get into the engine to help with EGT's and efficiency.

 

[Ozymandias]

Thank you, is on my list.

 

[MojaveJoe]

Thanks guys. That's a load off my mind.
Drivin' stock now and loving it....
Joe