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need help diagnosing spark plug problem ASAP

Old 03-08-2006, 12:37 PM
  #1  
Captain Redbeard
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Default need help diagnosing spark plug problem ASAP

im supposed to leave in 2 1/2 hours to go to my dyno tune and i was gunna swap the plugs out because i jsut changed the injectors and i wanted a fresh set for the tune.

so i get them out and the drivers side look BRAND NEW and the passenger side is BLACK, dry soot black, not wet oily black. i dont get it. i found a fuel leak last week at the fuel rail and fixed that and it still did the same exact thing.

the car was running great until i got in the gas a little and then it started to feel like it was misfiring again, which is another reason why i checked the plugs.

i had MSD coils, i think i may swap those back in, stock coils are in currently

im also thinking maybe its a bad front o2 sensor causing the pass bank to richen up too much
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Old 03-08-2006, 01:03 PM
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You may have to try some elimination and parts swapping to isolate it. Or, it might be something simple If you have a scan tool, that will definitely help narrow it down.

With a scan tool, look at the long term learned fuel trim values. If the sooty bank is correcting for a perceived lean condition, check for exhaust leaks on that bank. Extra oxygen to the O2 sensor will force that bank to run rich. Otherwise, you can try swapping the front sensors left to right, and seeing if the problem progressively shifts to the other bank (rule out the O2 sensor). A sluggish or failed sensor will generally trip the check engine light.

A bad coil or leaking injector would affect one cylinder only - if you have a common issue with all 4 cylinders on one bank, look for everything that's common.
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Old 03-08-2006, 11:47 PM
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i replaced all the plugs and swapped in some new o2 sensors and the problem was solved, the right bank was still the factory one and i think it took a ****.

the light came on last week and i just cleared it, didnt think twice about it because it comes on from time to time anyway. i had a fuel leak at the rail last week and swapped some 24lb ones in with all new seals and took care of that problem.
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Old 03-10-2006, 01:16 AM
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Simply swapping in 24lb injectors might cause you some problems. They will have to tune your computer(chip) for those bigger injectors, unless your MAF is calibrated for those injectors.

Even though your specific problem looks to be caused by the O2, your probably running pretty rich with those injectors(unless you did one of the things above).
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Old 03-11-2006, 10:56 PM
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the problem had started before i even put the injectors in, the problem has been fixed and the cars already been to the dyno and properly tuned for the injectors, but thanks for the advice!
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Old 03-31-2006, 02:07 PM
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Glad you fixed your problem. How many miles are on your car TJs98GT? Did you tune the car for the injectors with the bad O2 sensor or did you get the tune after your problem?
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Old 03-31-2006, 02:33 PM
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What'd it put down?
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