Alex51

I own a 1996 z28 camaro and recently did a tune-up (spark plugs and wires, oil, and air filter). After about 2 weeks, the check engine light started to go on and off. It would go on for a couple days then turn off and so on. So, I went out and bought an obd II code reader and it diagnosed the problem as an enigne misfire. I tried it a couple of different times and it came up one time as the 7th cylinder misfire, then the 3rd cyclinder misfire. I noticed that the misfire is coming from the left side of the motor. There is also a loud noise almost like a vibration coming from the rear of the motor right near the emissions canister. I replaced the optispark, rotor and thermostat, and none of those seemed to solve the problem. I tried checking the O2 sensor by the 7th cylinder with an ohm meter and that seemed to be fine (althought it didnt seem very accurate). I have no clue what to do. Does anbody have any suggestions????

ricehammer

Maybe your wires got too close to the manifold and burned through. To check for arcing, start your car up at night and have a look around under the hood. If your wires are arcing chances are you'll see the arcing and possible hear it also. What mods do you have? Headers are bad about burning plug wires.

Injuneer

What "emissions canister" at the rear of the engine are you refering to? The charcoal canister for emissions is in the driver's side rear fender.

As far as the "O2 sensor by the the 7th cylinder"..... do you mean the driver's side
O2 sensor, mounted in the base of the exhaust manifold? If so, what test did you do with an ohm meter that told you the sensor was "fine"?

Almost sounds like you may have cross-firing between the #3 and #7 spark plug wires.

Alex51

what exactly is arching?

Alex51

Yeah i guess i was refering to the charcoal canister. The buzzing seems to come from around there.

And I tested both the sensor and the plug that goes into it. The ohm meter was really hard to use though so again i dont know how accurate the readings were.

Okay so i bought another set of spark plugs and when i took out the old ones (well there not really that old) There was black stuff and oil all around the tips of the ones on the left bank's side, but on the right bank the plugs seemed normal. I put the new ones in and the check engine light went off but the engine still isnt running like it use to. It runs really rough and doesnt have a very good throttle response almost like its a v6.

I also noticed that there seemed to be unburnt fuel. I can smell the fuel outside of the car when it is running. Not to mention it is backfiring coming out the exhaust.

Could the plug wires go bad. Ive only had them for a month or so and there not laying on the exhaust at all.

Injuneer

So you have a "buzzing" coming from the drivers side rear fender, where the canister is located? I thought you said the noise was from "the rear of the motor right near the emissions canister." There IS NO emissions canister at the rear of the motor. Its in the back of the car.

Again... HOW did you test the O2 sensor with an ohm meter? What did you measure the resistance of? What readings were you looking for? I'm not aware of how you verify the health of an O2 sensor with an ohm meter.

Its running rich on the drivers side. May be the result of a "false" lean condition. That could be caused by an exhaust leak before the O2 sensor, or excessive misfires. Again... if you have problems with #3 and #7, check the plug wires for crossfiring. Run it in the dark, pop the hood and look for arcing. Arcing of the wires can be caused by an excessive spark plug gap. What did you set the plug gap at?

Its running pig rich, and I'll put my bet on ignition problems on the drivers side of the engine.

Alex51

It is the canister that the exhaust manifold on the left side connects to.

I just did what the repair manual did. I guess i didnt do it right. Is there another way to do it?


I gapped every plug .050. So if there is ignition problems, any suggestions on what part to get?

Thanks for your help. really appreciate it.

hosspwr94

I believe the plugs are supposed to be .035? correct me if I am wrong!

Injuneer

That's the driver's side catalytic converter.

Just tell us what you did.... what did you measure? What values did you get?


Now that we determined that you have a "buzzing" in the catalytic converter on the driver's side, you have to check and make sure you don't have a leak at that point. And that the convertor is not plugged up.

Alex51

okay so first i tested the oxygen sensor. The repair manual says that on a cold engine the sensor should produce a signal of .1 to .2 volts. It was at .1 volts. Then i tested the connector and recieved 3.7-3.9 ohms. The repair manual says it should be between 5-7 ohms. Maybe thats too low?

ricehammer

Doooh - arcing

Injuneer

Was the engine cold or the sensor cold? If the sensor is cold, you should see the voltage supplied by the PCM, which is .450V. The sensor does not produce any voltage of its own when it is cold. Problem is, a multi-meter (not an ohm meter) has to be a very high impedance meter to avoid damaging the sensor, and even with a high impedance meter, you may only see ~0.350V cold.

If your AIR pump is still functioning, at cold start, with the pump running, the sensor should read ~0.450V when the engine starts, then slowly drop below .100V as the sensor begins to warm up. If your AIR pump is not functional, you will general see the voltage start to climb above .500V, since a cold engine will be running richer than the stoichiometric 14.7:1, due to cold start enrichment.

With the sensors and the coolant warmed up, and after 205-seconds from cold start, the PCM should enter closed loop, and the sensor will start to swing back and forth from lean (as low as 0.0xxV) to rich (as high as 0.9xxV) 9 times per second. At that point, your multi-meter will not be able to reliably measure the voltage. That's why its much better to scan the PCM and observe the voltage reported by the PCM.

I've never tested an O2 sensor resistance, so I have no idea what the reading is supposed to be. I think what they are telling you to check using the resistance it the heater cricuit in the sensor. Chiltons indicates that reading should be about 10-15 ohms at 79*F.

Alex51

I started testing my fuel injectors to see if they were working properly and noticed the 1, 3, and 7 injectors were not working. As the car was running i would pull the clips off an injector one at a time. The ones that were working you could hear the drop in RPMs. The 1, 3, and 7 injectors had not impact on the motor. Does this mean I should get new fuel injectors or the clips that attach to them? and do you think this could cause the misfire?

Injuneer

Key on, connectors off the injectors, check the pink wire in each injector harness connector for 12V. Then with the connectors still off, check the resistance of the injectors across the two pins. Should be in the range of 12-16 ohms. If it passes all these tests, get a set of 'noid lights and verify that the PCM is providing the ground pulse to fire each injector. Use a stethescope to verify each injector is clicking.

Your scanner should have picked up P0200 for injector circuit malfunctions. The exception would be if the three injectors with problems are simply plugged up with contamination.

But the fact that the RPM did not change when you pulled the clips off those three injectors does not mean with absolute certainty that its the injectors causing the problem. I could still be 3 bad plugs or three bad wires.

And yes... if an injecotr is not working, it will definitely cause a misfire.

Alex51

The injectors and harnesses all passed the test. I dont have a set of noid lights. Should I get a pair?

Do you think the rattling from the driver's side cat could be clogged and that could be causing the misfire?