misfire from cylindar to cylindar diff each time - Team Camaro Tech
Troubleshooting Diagnosing problems done here.

 
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post #1 of 8 (permalink) Old Sep 7th, 02, 02:04 PM Thread Starter
 
Join Date: Sep 2002
Location: gonzalas,la,u s
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I have had a 85-305,a 96rs,and now have a 97rs.Both the 96 and the 97 have had problems misfireing.My current problem has been a misefire detected in 3 different cylindars at different times.Now it has settled on cyl.4.I have changed my pluggs, my wires, and my coils. What more could it be?Again this is a 97 rs with a 3800 v6. Same as the 96 rs.
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post #2 of 8 (permalink) Old Sep 7th, 02, 02:46 PM
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what about the cap have you changes it an rotor to. also check for vacum leaks around the intake or if brake booster is leaking down creating a lean condition over that cylinder.
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post #3 of 8 (permalink) Old Sep 7th, 02, 03:03 PM Thread Starter
 
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Location: gonzalas,la,u s
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what cap? this has electronic ign. you have 3 pairs of coils {3 caps 2 coils per cap}and each have been changed. and there does not look like there are any leaks.And if I run interstate to work at my usual 75 for 50 miles it runs better once i get off than if i had just drove around town. hesitates excellerating the most between 40-60 and if im trying to punch it to pass at any speed. if i only give a little gas no problem just when i put it under a load or demand for performance.i feel stumped. is this a common problem for these models? this makes two that have had the same problem.
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post #4 of 8 (permalink) Old Sep 8th, 02, 02:57 AM
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1taz, Welcome
It sounds like you must be using a scanner if you know what cylinders are misfiring. Are these random misfires setting a "check engine" light or are they stored in history?

If your driving the car in low gear and mashing the accelerator to the floor you could be hitting the rev limiter and in so doing can cause the PCM to shut down cylinders.

If this isn't the case have you done a compression test?
Fuel pressure test?
How about the quality of the gasoline you use?
What kind of spark plugs are you using and are they gapped right?
Are the spark plug wires routed correctly?
Are there any other codes stored?
Check your engine grounds and make sure they are clean and tight.
You could have a crankshaft position sensor problem.
There are a quite a few things it could be. Post more info.
What is the mileage on this engine?
Have you changed/modified anything? Like MASS airflow sensor.

Drew

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post #5 of 8 (permalink) Old Sep 8th, 02, 03:01 PM Thread Starter
 
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I have checked codes by active reading, And ihave pulled history and reset then pulled again after running it.like i said in my opening request for much needed help first time a felt a problem and the light came on i checked it and it was cyl 3.Next time it was 5.So I changed the type of gas i was using.That helped some then cyl.4 started acting up.I have since changed wires,coils,and plugs.The plugs are botch platinum 4's.My next thought is to change air filter,fuel filter and check injector.I have been told that it could be something along thase lines.Or rings in that cyl.but if that was the case why the trouble first in the other two cyl. And in my 96 that i had previuosly the same thing .
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post #6 of 8 (permalink) Old Sep 8th, 02, 05:58 PM
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Hello 1taz,
I was just down in La, Baton Rouge, last week. Too humid for me! I don't think your problem is caused by fuel or air filter. A good place to start is to follow Drew's advice on the previous post. Do a compression check, then do a dynamic compression check along with a snap throttle test and compare results. Look in the General Camaro Tech section. I posted to spongebob last week under "low cranking pressure" for details on how to do the test and why it works. If you have a problem with an individual cylinder breathing ability the dynamic test WILL point it out. Remember the direct ignition system fires two cylinder at the same time, so if you are sure about your condition of your wires the coil if weak would be misfiring two cylinders usually. It fires on the power and exhaust stroke, it was simplier to make the system this way and it doesn't take much energy to fire a cylinder on it's exhaust stroke compared to compression or power stroke. Anyway I think a bad coil or coils isn't your problem. Did you replace the ignition module that they plug into? That has been a very troublesome unit for GM as has the ECM or computer. I've had both go bad in the past. I've also had crank sensors go bad as Drew suggests. If the monopole (crank sensor) is losing it's magnetism or is damaged placing the tip too far away from the triggering mechanism it can cause these kinds of misfires. The sensor usually isn't too difficult to replace or expensive from my experience. It's unfortunate that you've had the problem on two different vehicles now.

Dave
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post #7 of 8 (permalink) Old Sep 9th, 02, 04:32 AM
 
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THATS WHY I LIKE THE OLDER CAMAROS MUHAHAHAHA



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post #8 of 8 (permalink) Old Sep 9th, 02, 02:44 PM
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1taz,
How do you relate the last car you had with a similar problem to the car you have now? It could be two different problems.

Stop throwing parts at the car and figure out whats going on.

Have you taken a fuel sample? I had about six ODBII cars come in at one time that wouldn't even run and found out right away they had water in the gas tank. Random misfires? Anything is possible.

Step back and go basic. A gasoline internal combustion engine needs spark, fuel, & compression. I don't care how many gadgets Detroit sees fit to put on them.

I'm not trying to down you, it is really good you want to find out whats going on and if it is your daily driver that makes it worse because you depend on it.

Do the static compression test on a warm engine and go from there it will tell you where you stand.

Drew
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