RPM drop during steady throttle

[darklotus42]

okay first off i have 95 cutlass 3100 Gen 1.5. 60k mi. i recently removed the stock air cleaner box and installed a spectre cone filter in its place. i have started to notice something strange while driving. i will be going down the road between 40-50mph at a steady throttle of about 2200 rpms and all of a sudden the rpms will drop down to about 1700. pretty sure its not the tranny shifting or tcc (tcc shouldnt lock til 55mph) there was an issue with my air filter popping off the intake hose but i have since fixed that problem although i did notice an oily residue inside the hose running towards the throttle body. where is this stuff coming from? could something have been fouled up that is causing some sort of ignition problem? also not sure if this is related but it seems ive only been getting about 15mpg at best although i run AC alot.

[RobertISaar]

TCC will lock as early as 45MPH depending on how heavy you're leaning into the throttle. 2200 sounds like 4th gear without TCC lockup, 1700 sounds right for 4th with TCC locked.

[Galaxie500XL]

Like Saar said, TCC lock sounds about right...

 

But that 15 mpg thing sounds like a bigger issue.  I get 21-22 mpg consistently out of my LQ1 with 250,000 miles on it.  Might be time for a bit of a tune-up? 

[darklotus42]

any ideas on the oily stuff in the tube? i have now noticed that it does it pretty much at any speed above 40 and that if i start to accelerate and then hold steady throttle it does it again along with a lag on resuming accel.

 

also i just changed my plugs n fuel filter---still had the Original factory filter n plugs...hadnt been changed in 60k...hopefully that shuld help mpg...anything else i should do to help mpg?

[RobertISaar]

oil in the intake tubing is almost always going to be oil sucked up through the PCV system, though once or twice, it has been transmission fluid pulled up through the vacuum modulator.

[oldparts]

plugged cat

[Psych0matt]

plugged cat

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