I'm having trouble identifying my problem when I start my civic it idles rough like I have a misfire. But after I Rev the engine for a second it goes away. And have noticed a change in acceleration and fuEl consumption. Any ideas? I've chaneed the iac, plugs, and plug wires. I'm at a loss. I've see so many things it could be. Would like a list of possibilities starting with most likely if possible

 

Is your check engine light on?

 

Yes but the only code it throws is upstream o2 sensor due to cracked east manifold. I've tried to put high heat jb weld on it but it just fell off after a couple days

 

Did you clean the crack area of any corrosion before applying the JB Weld? During the time that it was on, did the code go away?

Try and get that code to clear first.

Check the contacts on your distributor cap and rotor.

 

I did see that and was wondering if I could clean my distributor before I decide to spend the $100+ on a new distributor. Could it be that, when I changed my timing belt and water pump, I didn't use a timing gun and adjust my distributor?

 

Fix the crack first. The ECU remembers readings from the O2 sensor while the engine is running, and uses those to set the A/F mixture on the next start. So it's not only hurting your mpg and performance, it could be the reason it stumbles at startup.

This is why the OBDII engines run strangely the first time started after the battery has been disconnected. Which can be another reason for your problem-- if the memory circuit fuse is blown the ECU resets every time the key is turned off.

I would not go to the distributor just yet if it is not misfiring later while running. But you do have to time it with a light.

 

Thank you for all the info. I finally got the timing belt correctly set. I was off by quite a bit. All is running well now.