Rep Power: 0

I just bought a 89 civic and the check engine lights on. Ill be driving it and the light will come on and itll hesitate a little. When i get to a stop light everything seems fine, idoling normal, sounds normal, normal, until i go then it hesitates not wanting to go anywhere. As soon as i let off the gas the engine nearly cuts out but immediately returns to the usual idol and goes like nothing happened. It threw code 1(02 sensor), 4(crank angle) and 12 (EGR system). Thing about the 12 that doesnt make sense is its a code for cal emmissions and im not in cali. I feel like 1 is most prevelant to my problem am i rite? If so theres lots of things that could throw up this code and i want to test the 02 sensor before replacing it. My chiltons manual has diagnosing instruction for the 87-88 models 02 sensor but not 89. How do i test it to see whether or not its bad?

 
Rep Power: 235

EGR system is controlled by the ECU, which gets some of it's info from the O2 sensor and crank angle sensor. I think what is happening is the crank angle sensor has gone bad or is unplugged or has a bad wire/connector, throwing off the O2, which in turn throws the EGR off. Although, it could be the O2 sensor came unplugged or has a bad wire/connector. Start by checking connections at the O2 sensor and if you have an EGR then remove and inspect/clean the solenoid, the EGR vacuum solenoid and the EGR ports.

EGR solenoid looks like this:


EGR vacuum solenoid looks like this:


Then try checking the crank angle sensor. It's under the lower timing belt cover, which is a PITA to get to.

Then get a factory service manual here so have wire diagrams to diagnose for bad wires: http://www.helminc.com/helm/homepage...vlB&usg=AFQjCN or if that's too expensive, try local craigslist, or eBay for a used, down-loadable version, or CD of the manual.