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05 Impala running issues

So I’m having an issues with my 05 Impala. It starts and idles fine with no abnormal shakes or sounds. When the engine warms up, when traveling over 30mph it starts to chug and stall like it’s running out of gas. I’ve changed the fuel filter, fuel pump, cleaned the MAF sensor (looked good, no broken wires and connector was fine), new air filter, crankshaft position sensor was replaced 6 months ago, cleaned fuel injectors and I’m out of ideas. I get no check engine light to give me a little direction. I think it may be a catalytic converter issue and I hope it’s not. Any ideas would be greatly appreciated as I’ve invested a lot of money in the last year to keep this thing going for the long haul.

Given what you’ve already replaced/repaired that sounds like a pretty good bet. You can check it a couple of ways, unhook the exhaust before the cat and drive it to see if the problem goes away - do this outside the city, it will be LOUD. Of find a place to test the exhaust pressure between the engine and the cat. It should be very low, even at full throttle - 2-3 psi

Aftermarket cats are not all that expensive. $155 at Rockauto

TPS (throttle position sensor)?

“When the engine warms up, when traveling over 30mph it starts to chug and stall like it’s running out of gas.”

It has never actually stalled, has it?

I would check the TPS. I’ve seen them become faulty without lighting a Check Engine Light.

It has actually stalled a bunch. Usually it will chug for a few miles and then the longer it runs the higher the chance of it stalling and shutting the engine off

Also I forgot to mention that under the car seems to get much hotter then any car I’ve worked on and has since we bought the car 2 years ago.

Here’s why I don’t think this is the problem, and correct me if I’m wrong on this, but when the car is parked even after it’s warmed up, if I rev the engine up I don’t have any issues. It seems like it’s just when it’s under load.

So, when the engine is cold, there is no problem…you can go as fast as you want, right?

Seems like it. I’ve got on it pretty hard when the engine is cold and no problems. Usually takes about 4-6 miles for it to start happening[quote=“insightful, post:8, topic:104689”]
So, when the engine is cold, there is no problem…you can go as fast as you want, right?

Try unplugging the MAF sensor and see if it runs better.

I did. Runs same and no engine light

Then I can only guess temperature sensor or O2 sensor.

Even with no codes?

Well, if you disconnected the MAF sensor and didn’t get a code, anything’s possible. I suppose it could point to a failed computer, though.

So I ran with a scanner and showed TPS was stable and didn’t suddenly drop or anything. MAF and MAP sensor looked good. Short term fuel trim would spike when it started to chug but nothing else abnormal

WAG Torque converter.

Have you checked for vacuum leaks? What do the spark plugs and wires look like?

Spark plugs are new and the wires look fine. No freying. No vacuum leaks that I can tell. I’m going to pull the o2 sensor and see if that helps to check the cat when I have the time

I don’t think this is the problem as the transmition was just rebuild like 2 months ago. Also it wouldn’t cause the engine to completely shut off either, right?

It could cause the engine to shut off, I did not see that referenced earlier, did you read through the link, it is overly broad, by design I suppose,
From the article
"Overheating – If you glance at your temperature gauge and it happens to be overheating, this could mean that your torque converter is malfunctioning. "
“Shuddering – If you start to feel shudders when driving about 30 to 45 MPH,”
“Increased stall speed – A bad torque converter will take the transmission longer to engage the engine, resulting in higher than normal stall speeds.”
“This will lead to irregular behavior such as poor fuel economy and stalling.”

Seems to describe everything in your complaints I have read, Did the torque converter get replaced?