Slow acceleration?

CCALE04

MEMBER
2011 CHEVROLET EQUINOX
2.4L
4 CYL
2WD
AUTOMATIC
171,000 MILES

About a month ago my equinox started not wanting to accelerate. It has had a CEL with code P0420 so I Replace the cat, pre and post O2 sensors, put new plugs in it, new air filter, removed the intake to clean the PCV hole out to make sure oil didn't ruin the new cat and I am still having the same problems with no CEL now. I have used a scanner to check live data and everything seems to be normal fuel pressure stays between 45-60psi, fuel rail pressure averages around 500psi at idle going up to around 1800 at wide open throttle, MAF show around.75lbs a min going up to around 10lbs at WOT, MAP is around 28inHG with the key off which matches ambient air then once started goes to around 10in if I remember right, O2 sensors are showing to be working as well that I replaced. Everything seems in range from what I can come up with the engine just keeps acting like its suffocating and can't pull itself. I am at a complete loss on what to try next with it not throwing a CEL now. Any help would be greatly appreciated. Thank you!

6 Replies

AL514

MECHANIC
4,792 POSTS

Hello, so this setup is kind of deceiving, there is a 2nd 3-way Catalytic converter about mid-way down the vehicle. It's a real bummer that they don't have another oxygen sensor behind it to monitor its performance. I will post the part numbers as well because they are different for California Emissions and Federal Emissions for the rear cat. The 2nd cat is the mid pipe just before the muffler. You correct on your diagnosis though.

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Sunday, August 18th, 2024 AT 3:58 PM

AL514

MECHANIC
4,792 POSTS

Here's the part numbers and I included the front cat info as well, the 2nd cat (diagrams 4, 5) shows its location, and if the front cat came out broken up due to it melting down, make sure to check for junks of the old cat in the rest of the exhaust. I'm really sorry they don't make this more apparent; I know how frustrating it is after all that work. Hopefully its possibly just pieces of the old cat restricting the exhaust.

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Sunday, August 18th, 2024 AT 4:05 PM

CCALE04

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21 POSTS

Can the secondary cat being clogged cause it to run lean? I pulled the plugs to check them and all 4 show its running lean and the car shows it is still pulling fuel in the trims. I unplugged the upstream O2 trying to get it to dump more fuel and it ran a little better but not like it should so I put another set of plugs in it today went back to AC Delco's instead of the Autolite iridium’s I had in it and replaced the O2 with a better brand to make sure it was reading correctly. So far, the thing that has helped the most to clear up the problem has been test driving it with the MAF unplugged all together (I thought the car wouldn’t run with it unplugged but apparently, I was wrong).

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Sunday, August 18th, 2024 AT 5:24 PM

AL514

MECHANIC
4,792 POSTS

If it's running with the MAF unplugged it's using a default strategy to run, I would drop the mid pipe and check if you can see through it with a flashlight. To make sure it's not melted down restricting the exhaust, you don't want to ruin the new cat, and if you keep driving it like this that's what is going to happen, so it's better to be safe than sorry, You can try even just dropping the front of the mid pipe so the exhaust has a place to go. If the exhaust has no place to go, then no air can come into the engine, it's not going to breathe correctly.

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Sunday, August 18th, 2024 AT 6:25 PM

CCALE04