Losing power but no codes

[SpiffWilkie]

I have an '04 manual and several months ago I was having some issues where the car was idling too high. I checked hoses, cleaned out the throttle body, and even replaced the IAC. The issue was intermittent and more annoying that anything.
Well, for the last few weeks I've noticed that I am severely lacking power. The CEL has not lit up once and I have no stored or pending codes. Again, I've checked hoses for vacuum leaks, checked to make sure there was nothing blocking the intake, etc. I still can't find any obvious cause. The way the car is driving reminds me a lot of how my van was acting recently before I replaced the cat, but that was accompanied by codes from the O2 sensors.

The way it's driving now, if I give it gas like I would under normal situations, the car just doesn't respond like it should. It accelerates much more slowly. It feels kind of like it feels like I'm in too high of a gear for the speed. If I give it more gas, the RPMs will go high and while the car speeds up, it's still obvious that the power just isn't there.

Any ideas what would cause this without throwing any codes? I have a scanner that I can log data with, so are there some recommended PIDs to monitor?

[avguy]

Did you buy this Aveo new? What I'm really asking is do you know the history of it? The '04 was prone to early timing belt breaks. Another big problem is the POS plastic thermostat housing which has caused numerous overheats for Aveo owners. If you don't know the history of your Aveo (or had one of those 2 problems), you might consider a doing a compression or leak-down test (which hopefully will show nothing wrong).

[SpiffWilkie]

Did you buy this Aveo new? What I'm really asking is do you know the history of it? The '04 was prone to early timing belt breaks. Another big problem is the POS plastic thermostat housing which has caused numerous overheats for Aveo owners. If you don't know the history of your Aveo (or had one of those 2 problems), you might consider a doing a compression or leak-down test (which hopefully will show nothing wrong).

I've had it for about 8 years, and it belonged to my brother-in-law prior to that.
I replaced the head about a year ago due to the infamous timing belt, and the thermostat housing was replaced not too long after following a wonderful coolant geyser.

[avguy]

I've had it for about 8 years, and it belonged to my brother-in-law prior to that.
I replaced the head about a year ago due to the infamous timing belt, and the thermostat housing was replaced not too long after following a wonderful coolant geyser.

I think you definitely should do a compression and/or leak-down test.

[ontarian_frog]

It could also be a throttle positioning sensor. The ECU wouldn't be able to calculate engine load and throttle angle if the sensor is faulty. It might not show a fault even if it's bad because it's drive by cable.

[SpiffWilkie]

I think you definitely should do a compression and/or leak-down test.

Just checked the compression. I'm not sure of the accuracy of the gauge (it's been through a lot), but the cylinders were all consistent at just over 120psi.

Edit:
My testing methods (in case I did something wrong).
- Ran the engine for a few minutes to warm it up.
- Pulled the fuel relay
- Removed all plugs

[Daox]

Did you open the throttle all the way when you were cranking the engine?

[SpiffWilkie]

Did you open the throttle all the way when you were cranking the engine?

Sorry, yes. I had it floored.

[SpiffWilkie]

It could also be a throttle positioning sensor. The ECU wouldn't be able to calculate engine load and throttle angle if the sensor is faulty. It might not show a fault even if it's bad because it's drive by cable.

I checked the voltage on the TPS. It read from .58 to 4.4. I didn't notice any issues as I changed the throttle position. The voltage changed smoothly, and I banged on it a bit and wiggled the harness to see if there were any drops in voltage.

[SpiffWilkie]

Would I be getting this noticeable of a power loss due to a bad cat without a code? I'll log the o2 sensors when I go home tonight and see what the graph looks like.