I have a 2003 Cavalier. I just replaced:
Plugs, boots, coils, ignition module, ecu, fuel filter, fuel injectors, map sensor, fuel regulator, iac valve..... Car has a rough idle... gets better if I run the ac. I keep looking at my scanner and the only thing that seems off is the ignition advance...

If I watch the ignition advance it jumps back and forth.... +3 +20 +4 +18 +7 +19 back and forth..... I'm thinking a loose timing chain?..... My compression is 170/170/170/160 Fuel pressure 60 Psi.

I just spent a ton of money on all these parts that made no difference... just want someone with experience to tell me if I'm on the right track... or were to look. I do have a scanner.

Is this an Ecotec 2.2 or the OHV 2.2, or something else? Also, is the advance changing at a stable throttle, like idle? I'll put my scan tool on my 05 Ecotec when it gets light outside and check mine in an hour or so. Any set or pending codes? Do you have freeze frame data?

Actually, it is light enough for my camera. Here's the highest and lowest I get on my 05 ecotec at idle when run for a few minutes... It is pretty cold by the Intake Air Temp and the coolant temp.

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Thank you for the response James.
It is a ecotec 2.2

So your ignition adv. does not jump around much, very little.

I feel like it wants to idle to low around 500 rpm. If I put the ac on it forces it to idle higher and runs better.

The other thing I saw was my tps is at 0. Yours is at 8.6... my tahoe is at 7.6... But that may be due to my cavalier is old and driven by cable to the throttle body, were your newer car and my tahoe are electronically controlled throttle body.

If I let the car idle I will get a P0302 code. Cylinder 2 misfire within a couple minutes. If I run the ac... no check engine light... but i do see a engine code p0300 random misfire code.

Everywhere I read people complain about faulty timing belts.... But my dad said if it were a faulty timing belt my compression would be bad. 170/170/170/160 is ok.