Bogging down

[Gilbertd]

Hello there! I’m new to this forum and thank you for letting me join. I own a 2007 legacy, but not GT. About a month ago it started bogging down when pushing accelerator pedal. Right now it idles fine but a soon as you try increasing rpm it bogs with like a heavy bass sound. It barely moves when put in drive. I’ve trailered it to a local shop and they replaced spark plugs, MAF sensor, fuel pump n filter, without any results. They couldn’t figure out what’s wrong with it. I brought it home and took catalic converter off and no difference 

check engine light is off

thank you for any suggestions in advance 

gilbert

[Yamon234]

This is probably a bit of a longshot but is the air filter clogged? Problems like these sometimes it helps to remember the 3 basics of combustion. Air, spark, and fuel. With the pump and filter done we can probably assume fuel is good. If it idles fine then the spark is probably good but it could theoretically still be wires or coil packs. This makes me think perhaps it's not getting the air it needs. I'm sure since they went through the trouble of replacing the map sensor they've probably changed the air filter. You could easily test this by pulling the air filter out, starting it, and giving it some gas. I've seen people who've put new air filters in and not unwrapped them causing the choking of the engine. Also never a bad idea to look for vacuum leaks. 

Everything I'm saying are things I would have assumed any reputable shop would have already checked. So if this solves your problem you should probably find a new shop from now on. 

[Gilbertd]

Thank you for the response! I took air filter out for a minute before I took it to shop with no change. Spark plugs were replaced with no result. When car first started bogging down it was like 2-3 quarts low on oil, dunno if this created a limp mode??

[Max Capacity]

That's pretty low on oil. Make sure you keep a close eye on that. Not good to get that low.

[Yamon234]

Yikes, +1 for what Max said. I'd almost be curious about the results of a compression test. But you'd probably have misfire codes if that was the case. 

Does it shake the car when bogging down? 

[KZJonny]

1 hour ago, Yamon234 said:

Yikes, +1 for what Max said. I'd almost be curious about the results of a compression test. But you'd probably have misfire codes if that was the case. 

Does it shake the car when bogging down? 

I was going to suggest looking at your thread with the similar(ish) problems, and this also sounds like maybe a throttle control/pedal issue.

[Gilbertd]

I hear about the oil, my son never kept an eye on it. It’s his car. It bogs down like there’s no air flowing into the engine. It even does it in park while trying to rev the engine . No shaking just a heavy base sound. Car idles normal

thanks again for responses

[silverton]

1.5-2 quarts of oil in the engine is absolutely NOT enough and it very likely has caused engine damage.

That is what intake backfire sound like.  You can remove the unmonitored catalyst and see if there are improvements, if there aren't any the next thing to look at is the mechanical timing, which involves removing the crank pully to get both timing covers off.

Edited December 29, 2022 by silverton

[Gilbertd]

I took the catalic converter off after I took it home from the shop with no difference, sounded identical idling n still bogging down when pushing accelarator pedal

[silverton]

Verify timing.  I'd be surprised if the monitored cat was bad without throwing a code, but it's possible.

[Gilbertd]

Thank you Siverton I let you know when I have the timing checked

[Gilbertd]

KZJonny How can I check if it’s a throttle/ pedal issue?

[KZJonny]

I'd guess it's a long shot, but being drive by wire, it couldn't hurt to clean the contact area on the sensor of the pedal. I've had great success with a product called de-oxit for cleaning electronics and connections.

I think there is also advice somewhere on the forum about unplugging the pedal connection to perform a reset, and also just trying to swap out with one from a known good car, or maybe a junkyard part. (I am just wondering if the ?potentiometer? on the pedal could be fouled or some such. This could also involve recalibrating the throttle body to the pedal, which should be pretty straightforward, tho I've not had to do it myself. (If the part number for the accelerator pedal matches that of and OB or non-GT Legacy they should be cheap and easy to come by.)

Given that the consensus seems to be that you're dealing with a mechanical problem, it may not be the solution, but it's an easy thing to rule out at least.

[silverton]

You can verify that by looking at the data.  commanded and actual throttle opening.