gjw@floyd.UUCP (Greg Wroclawski) (11/14/83)
Your Camaro with cross fire injection has a microprocessor based engine control module like every gas powered GM car since 1981. During cold starting and warm up the engine is running in an open loop mode. That is the mixture is determined by various engine sensors such as manifiold pressure throttle position and engine temperature. There is also an exhaust gas oxygen sensor. This is used during closed loop engine operation. It maintains mixture at the stochiometric ratio of 14.7:1 +/-.05 . This is done to keep the catalytic converter oxidation and reduction action at the highest possible efficiency. However, the oxygen sensor must be at or near normal operating temperature to function properly. When it does the ECM switches from open loop to closed loop operation. Therefore the comment someone made about altering temperature sensor output to compensate for mixture won't have much of an effect during closed loop operation. The problem you are experiencing may not be mixture related. The ECM also controls engine timing. The distributor has no vacumm or centripetal advance mechanism. The timing "curves" are contained in a calibration PROM in the ECM. So there might be ,some glitch in the hardware controlling any of the above which could create your symptoms. The ECM also has its own built in diagnostics. You should purchase a factory shop manual for more information. Briefly, by grounding a pin in a connector under the dash you activate the self diagnostics. The check engine light flashes out codes which indicate which of the engine sensors are bad plus some other things. A fault is logged in memory even if it goes away, unless it does not reoccur within 50 engine starts. Good luck, let me know what it was.