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Hello,

I am having serious headaches, I digress. The real problem occurs when i drive ;). The engine starts just fine cold, then I can drive 10 minutes until it starts bogging down. I have to be real easy on the throttle if I don't want it to start problems. When it does die, I must wait 10 minutes before i can drive it another mile or so. It runs a little hot for comfort(3/4 of the way to red line). The car is throwing no codes. I suspected it was a fuel issue, I have replaced the fuel pump and fuel filter(the old one was pretty dirty and the fuel tank was mostly clean inside). I'm still getting bogged down(me and the car lol). So I hooked up a fuel pressure gauge, it idles at 48psi, when I apply throttle it jumps to 53psi and when I drive above 60mph it gets 65+psi(scary). It seems as though the higher the psi, the more power it loses....I don't notice any smoke from the exhaust, though. At this point, I'm considering: 1)The fuel pressure regulator is bad(evap line has plenty of suction) 2)Another theory I have is that the catalytic converter is bad; I tested this by removing the o2 sensor(to release pressure from the presumably clogged converter) and took it on a drive and now the fuel pressure doesn't get above 56psi on the highway plus it doesn't bog down as hard. Although, the o2 sensor I took off was downstream from the converter, which doesn't make sense to me why I got the extra power. I am thinking about removing the o2 sensor upstream of the converter to be sure. Any help would be appreciated!
 

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2011 Malibu LTZ 3.6L V6 Red Jewel Tintcoat
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My first thought was a clogged cat as well.

Pop the upstream sensor and you'll know quickly. But don't drive a lot with it out since that puts very hot exhaust coming out of a hole that might cause issues nearby.
 

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Stop ****ing around with fuel pressure.
Its not a fuel pressure issue.

Like driven said, pop that front 02 sensor and go for a drive. Unplug the sensor as well. You cant do this test with the sensor removed but still plugged in. The car will run like garbage.

If when unplugged and removed the car runs better, plugged cat.
You said its running hot too. That really is pointing more towards the cat being the issue.

Remember an engine is just a big air pump. Its gotta inhale and be able to exhale. If you got plugged exhaust then the engine cant exhale the hot exhaust gases and that'll stay in the engine creating excess heat.

Want proof? Buy an exhaust backpressure gauge. Unscrew o2 sensor and install backpressure gauge in its place. Start engine and get it to operating temp. (Helps to have a helper revv the engine while you observe here)

You should have NO MORE than 1 to 2psi of backpressure at ALL RPM ranges. If when you rev it up you start seeing that needle go up past 2psi, your exhaust is for sure restricted.
Hope this helps

Sent from my SM-G975U using Tapatalk..

CMF EDIT: EDITED PROFANITY
 

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There are tons of people on other forums with exactly the same problem, and although replacing the cat helps a lot, the issue returns about a week later. One person figured out if you disconnect the EGR valve it runs normally right away, but the light comes on. I suspect it could be the EGR valve sticking open which ruins the converter as well but I haven't confirmed it by replacing the EGR valve yet. I did replace the catalytic converter and the vehicle ran perfect for a week and then the problem came back once the vehicle had been warmed up and run on the freeway, (EGR operating conditions).
 

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This person was here a year ago and they only posted once....and never told us what the fix was.

But its slow here and I am bored so....
Had a88 Grand prix... ran great.....next day clogged cat....wouldnt run at all. Doesn't make sense that his runs for about the same time....then the car acts the way it does... there are things that doesnt set a code and messes with the car...clogged cat once clogged shouldnt let the car run right....then not ....then let it run right.....sounds more like a fuel filter.....but you did that.... possible egr issues? I know a knock in the engine...will trip the knock sensor....and knock a ton of power out of it...by reducing timing.... wish they woulda said what their fix was
 

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Clogged cats usually they idle fine but have no power going down the road. My '03 had a clogged cat, it got traded in as miles where high and bought it cheap after a few years of use.
 

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Ya, got rid of my z24 because of high mmilage. .bought with .227k km scrapped at 301k km.needed all new lines. Ran and drove great.....miss that car..... cost me 300 bucks over 5 years......this malibu has been just over 3k...... worst car I ever owned....lowest km...bought with 90k km......188k now.


Sucks when that one big repair comes up and ya gotta ask yourself if its worth it
 
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