Jackstand here. Need advice. Trying to get my daughter's 2008 Chevy Aveo running well

[Jackstand]

I started out getting codes on my daughter's 2008 Chevy Aveo. I did a compression test. Cylinders were 150, 175, 175, 155. I did a leak down test. The Cylinders were 202, 220, 215, It was running rough. Code said to replace upstream Oxygen sensor. I did. It still through a code and was running rough. Said replace downstream Oxygen sensor. I did. It still ran rough. Replaced all spark plugs. Replaced Ignition coil and wires. Replaced timing belt - cranked it around 2x by the crank bolt. Double checked the positions on the cam gears and crank and I was off a tooth. Redid the belt, cranked it around 2x and everything was perfect. Buttoned her up. Still ran rough. Do these compression test numbers mean I have a bad valve, or not enough compression in the #1 cylinder to have it fire correctly?

[EAD15]

What codes did you get?

[hunterboy149]

I started out getting codes on my daughter's 2008 Chevy Aveo. I did a compression test. Cylinders were 150, 175, 175, 155. I did a leak down test. The Cylinders were 202, 220, 215, It was running rough. Code said to replace upstream Oxygen sensor. I did. It still through a code and was running rough. Said replace downstream Oxygen sensor. I did. It still ran rough. Replaced all spark plugs. Replaced Ignition coil and wires. Replaced timing belt - cranked it around 2x by the crank bolt. Double checked the positions on the cam gears and crank and I was off a tooth. Redid the belt, cranked it around 2x and everything was perfect. Buttoned her up. Still ran rough. Do these compression test numbers mean I have a bad valve, or not enough compression in the #1 cylinder to have it fire correctly?

How about in-take. Namely MAF, PCV, Throttle body. Lastly, what brand/grade of gasoline does she use?

[Jackstand]

What codes did you get?

At first I got 0300. I pushed on the plug wires to make sure they receded erase the code and drove it again and I got 0301.

[Jackstand]

I have not done anything with the MAF, the PCV, or the throttle body. I buy my gasoline at Costco.

[Jackstand]

I have some MAF cleaner, so I will start there and see what that does. Thank you.

[Jackstand]

I have some MAF cleaner, so I will start there and see what that does. Thank you.

I searched for a MAF sensor and could not locate one. Searching on the Aveo forum I found a posting that said there was no MAF that this year of car was a MAP controlled engine. That being said, I will google how to clean a MAP sensor

[hunterboy149]

The 06-08 Aveo has a combined MAF/IAT sensor (Mass Air Flow/Intake air temp.) located in the rubber duct, between the air filter
and the throttle body.
I am NOT sure that can be clean or not??
If this turns out to be the problem, and is replaced, you need to let the auto go thru the "idle learn process", so it still may not run
at full performance, until a few cycles are complete.
Finally, make sure that the Costco gas is at least 87 octane.

[Jackstand]

Thanks, Hunterboy149, I did find the IAT when I took off the rubber tube from the air cleaner box. I did go ahead and clean that with MAF cleaner. I have another PCV coming today and I will install that. I’ll look into how to clean the MAP just in case that is contributing to this problem. And thanks, I’m pretty sure I’m going to have to do a drive cycle after all of this change before, I’ll know anything. I appreciate your advice.

[Jackstand]

Just to follow up on this thread, I wanted to let you all know that your advice was great after I cleaned everything and replaced the PCV valve I went for a drive to complete a drive cycle and the engine ran perfectly. No codes. No rough idle. It didn’t even run rough as I went through the drive cycle. Thanks to you guys for the advice!