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93 cavalier firing on 3 cyl


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xler8
New User

Nov 19, 2009, 7:44 PM

Post #1 of 3 (1012 views)
93 cavalier firing on 3 cyl Sign In

I've got a 93 cavalier, 4cyl, 64,000mi
#1 cyl is not firing correctly. I can see it firing, but it runs the same with plug off as if it were attached. It will run well at times up to 1/4 throttle then back to 3 cyl. It has 2 coil packs so I don't know how the one leg of the coil could be good and the other bad. It almost seems as if the timing on cyl #1 is off. Didn't think that was possible, but I'm at a loss.
I already changed spark plugs and wires. In the process I found a vacuum leak in main line off intake which has been fixed now.
I checked the body ground by running another one and that didn't fix the issue. I even went as far as to run a ground jumper from the battery to the ecm.
One thing I didn't check because I was thinking ignition problem is injector. I'll out a noid light on it in the morning to verify signal and listen to it.

Problem first started as car was warming up at an Idle and it suddenly went really rough. No overheating.
Only code it's throwing is for the ac which has been removed from the car. Live data stream doesn't show anything that jumps out as abnormal.

Any help would be greatly appreciated!
Thanks!


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Nov 20, 2009, 3:55 AM

Post #2 of 3 (1006 views)
Re: 93 cavalier firing on 3 cyl Sign In

You need to test your spark using an adjustable spark tester so you can test the capacity of the spark. You should be able to open it to the 20K mark and still get a good spark. If you do, then you need to check compression on that cylinder. If both of those check out OK, then we look at the injector.





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xler8
New User

Nov 21, 2009, 11:52 AM

Post #3 of 3 (998 views)
Re: 93 cavalier firing on 3 cyl Sign In

Looks like a coil, spark was weak and intermittent. Thanks for the help!






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