Missing/bogging after hard driving.

[LegacyDeluxe]

I'll cut to the chase......


Last two nights, I've been called into work (emergency related), and had to drive a good solid 15-20 min very hard.....pushing it on sides streets, and between 90-100 on the interstate. By the time I get to the general area I need to be, and off the interstate, I notice at slower speeds the engine bogs or stumbles sometimes during acceleration.
The first night, I thought it was due to the fact I was seriously on empty and fixing to run out.....or sediment in the tank getting close to the screen filter on the pump. However, tonight, on a full tank of gas, it did it a little bit.

I bought this car a month ago, and it looks like it's had a tune up just before then. However, when I get time this weekend, I'll still pull the plugs for a look.

Any thoughts?

[Grafton]

what year, model, and mods if any?

[LegacyDeluxe]

bone stock 99 Legacy L automatic 2.2

Actually.....the upper airbox in front of the throttle body has no filter.......I was thinking they come stock with a filter. Not really a "mod" per say, but something to note. I seriously doubt that's causing it though.

I know these cars are known for bad grounding, but I would think it'd do it more often if it were that. Of course, there's the other commons......bad O2 sensor, plugged cat, bad plugs/wires, or maybe a vacuum leak. Still, any of those should be showing up at all times, usually.

I dunno. Just thought i'd run it by the forum before diving in too deep.

[LegacyDeluxe]

Often people point fingers at fuel filters quickly under these symptoms, but rarely have I seen a fuel filter actually end up being the MAIN culprit.
However, that said, the fact it was worse the other day after a low tank.....I just wonder if something did get stirred, and the fuel filter does have something to do with it.

[ouch1011]

I'm going to say detonation/heat related problems due to driving the car hard for an extended period. When detonation occurs, the PCM will retard the ignition timing and that will result in a slight loss of power. Next time you fill up, try running mid-grade and see if it helps.

[Grafton]

In that line of thought, also give your car a sea-foam treatment, it helps burn off carbon from the combustion chamber which might be causing some of the above if that's happening

woo insomniac 4 am post!

[LegacyDeluxe]

Well.......I'm almost embarassed to admit this.......but given the this is the first automatic I've owned in a person vehicle.......

I'm almost leaning towards the transmission. I think it's shifting sporatically....in the case, making odd downshifts....or sometimes shifting up when the RPMs aren't high enough, causing it to fall on its face.

Slightly suspicion of the lock up torque converter not disengaging.

[ouch1011]

Shift behavior like that could be due to high transmission oil temperatures. The TCM will start modifying the shift and tcc patterns and timing well before it will actually turn on the AT Oil Temp light, as that is the equivilant of basically "pegging" the temp gauge.

[Huffer]

Time for an inline AT cooler...

[Grafton]

when was the tranny fluid last replaced?

if you have no idea go ahead and replace it, if you know smell it to see if it smells burnt, and replace it if it does.