96 Cavalier headache


Old 01-12-05, 08:18 PM
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96 Cavalier headache

I have a 1996 Chev Cavalier with a 2.2 four. I recently bought the car and replaced the head gasket (it was dribbling coolant out) and the car ran great. One of the injectors was, however, leaking gas and I replaced it with a new one (it sounded like one or more of the injectors were clicking too loudly; and it seems to have gotten better since I replaced the leaky one.) I now have a new problem, though, as the car will start, run, and idle just fine until the engine warms up. When it gets warm, the engine starts sputtering and acting like one of the plug wires has come undone, and I am getting an OBD II code 300 (engine misfire). This started right after the I put the new injector in. It runs fine at driving speed though. Assuming it to be an ignition problem, I have replaced the plugs, wires, and the two coils on the ignition module. It is getting pretty expensive to continue to replace stuff till it works (and so far it hasn't fixed the problem.) I now wonder if it is in the injection system....anyone got any ideas?
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Old 01-13-05, 06:19 AM
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some testing...

...with specialized equipment might be in order. testing injectors involves finding out two things...is the injector working electrically and is it working mechanically.

mechanically they have to seat and therefore seal up when not activated...installing a pressure guage and pressurizing the system by turning on the key and then watching to see if the residual pressure drops will tell if one is not sealing correctly. also...an injector must open correctly to flow the correct volume of fuel when it's being activated...this test is done with the pressure guage connected and then triggering the injector with a special tool and calculating the pressure drop. if the pressure drop isn't correct then some electrical investigation might be necessary...

electrically...the injector is a solenoid with windings that must flow a certain amount of current to produce the correct magnetism to get the correct mechanical movement inside the injector. if the coil isn't up to par, it won't flow the correct amount of fuel...a test is done with a tool that will activate the injector and allows for voltage drop measurement (which is an accurate method of evaluating the electrical characteristics of the coil). in the case of a shorted or partially shorted injector winding...the ecm may also be damaged. it may be that you need a pro... a really diagnostician, for this one. as you've duly found out...sometimes it's cheaper to pay for good diagnostics than to install what appears to be the most likely cause of a problem. good luck...
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