Cobalt SS/NA running rich
 

Hey new member here,
I have a 2007 Cobalt SS/NA 2.4. It's been slowly losing power over the last month or so and the check engine light has been on and off. I'm getting P0300 Random- multiple misfire detected, and P0172 Bank 1 System too rich. I replaced both O2 sensors and it helped some, but today when I started it up the fan was running near full power and the car doesn't want to accelerate. When try the rpms go up and then fall like its straining to go. I'm thinking maybe the cats clogged? I do have a scanner with datastream. looking for help for how to proceed. Thank you!

Do you have an aftermarket intake or any mods? Are those the only codes you are throwing? Have you don't anything with the MAF sensor?

if you drove it with misfires for too long its possible that you damaged the cat, yes.

Yes I have a GM performance short ram intake and I replaced the maf about 2 months ago.

Sometimes certain intake configurations can skew the readings on the MAF enough to throw off your fueling, is why I ask.

I was also thinking maybe the intake manifold gasket could be leaking? the car has 180k miles maybe I should have opened with that.

Leaky intake manifold would make it run lean at idle if anything. It's running rich so it is dumping fuel thinking there should be more air than there is which would be plausible with a leaky manifold if you had boost but you are NA so air can only leak in not out.

So your issues started after the intake?

Actually its had the intake over 100k miles the previous owner did that, I did clean the air filter a couple months ago and that made a substantial improvement. I checked the maf thinking I over oiled but its reading fine

thanks for explaining. that makes sense

Clean it anyway. Get some maf cleaner.

They need to be absolutely spotless and should be cleaned soon after oiling a filter.

Okay I will, I think I have a can somewhere. update in a few.

Okay so I finally got around to cleaning the maf, unfortunately didn't seem to make a difference. I was concerned about exhaust leaks so I ran some seafoam through and sure enough there was more smoke coming from the headers than the tail pipe. I took the cover off the headers and theres a big crack running down the middle. looks like the gaskets bad too. Can an exhaust leak cause the car to run rich? I would think the opposite but I'm a newbie.

Yes it can, it can dilute the reading to the o2 sensor causing a rich bias.

Oh okay! And this morning when I backed out for work the rpms were erratic and then it stalled. once it warmed up it seemed to be better but I guess I'll have to replace the headers.