I have a 2003 Civic DX with the 1.7 and in automatic with 210k miles. I am having trouble diagnosing the problem with my car. Pretty randomly (but more often when its it's hot and humid outside) my car will loose much of its power and it will start jerking pretty intensely until it stalls. Before this happens I usually notice them RPM jumping up and down by a few hundred as well as falling more quickly when I let off the throttle. Once it stalls I can crank it, the motor will start for a second and then die unless my foot is on the gas. Usually if this happens I can let it sit for 15 minutes and it will start up no problem but will still be low on power. The car also hesitates to start when the engine is warm, but is perfectly fine when its cold. The engine will also get very warm if I leave it running while parked for 10 minutes.

I got the code scanned at Autozone and it said p2004, which I believe is an issue with the IMRC, which I am pretty sure this car does not have one. I've read that the IAC valve can throw this code.

So far I have put new plugs, replaced the main fuel pump relay, and cleaned the throttle body and IAC valve. When I did the cleaning, my engine light went away and the car ran pretty good for about a week before it came back and I started having issues again.

I am considering replacing the IAC valve, but cash is a bit tight at the moment, so I don't want to replace it if that won't solve the issue. Any insights to this would much appreciated!