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Discussion Starter #1
Hello again everyone. Still trying to nurse my '97 ws6 m6 back to a healthy beast. Bought he in a state of neglect. I replaced plugs and wires, properly. I've been getting a random misfire code so I've made sure there isn't any burnt wires, all good. I dohave Hooker lt headers so no o2 sensors are present on manifolds. Codes are po140~po160. I'm also receiving po141~po161, i know these are for sensors under the car. I have no cat either.
Now. I began removing plugs and found that all 4 on drivers side are black. Removed #2 and #4 on passenger side, look great. Obviously not fuel pressure or injectors. My question is..... Can the driver side o2 sensor be bad, dumping to much fuel and causing misfire? I was trying to avoi swapping the sensors so i don't have to one again remove the plugs and clear them. They've got about 200 miles on them. The car seems to run fine on short trips. I have an obd2 so i can clear my codes after trouble shooting. I expect to see bank 1 and 2 sensor #1 on each side do to headers and no sensors present. So are my #2 sensors the culprits? ????? Thanks. Greg
 

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Id say the biggest sign would be the car running rich on only one side of the motor in all cylinders. Talked to a few friends today including a vette and a z28 owner, my father which is a great mechanical mind and noone else has had this problem wtf!
 

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Since i pulled all the plugs i did another compression test 180 ish on all. When i first bought the car they all tested at about 155. I know the car sat for a while. I was researching plug gap. They were a bit variable. Around .055. A bit to much gap. I know stock is .050 but mine isn't stock. To my knowledge, full exhaust 4.10 gears. Not sure about any internal upgrades. Any suggestions on plug gap?
 

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You might want to put car on a scanner that does running sensor scans. See what your o2's are reading, as well as fuel trims.

If you don't have a scanner that does running sensor scans, may I suggest the free obd2 scan program found in the sticky threads of 4th gen section.

You would also need an elm327 cable to hook car's dlc with usb port of laptop or notebook. Elm327 cables are available on ebay, amazon, etc.
 

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Hey cocobolo95, thanks for a response. You're about the only one that does comment on my threads. I recently got an elm 327 via Bluetooth and downloaded the torque app for my phone, amazing technology. Got hooker long tubes so po140-160 are constant. I am receiving po141-161 for the other two sensors as well, they are present. I have no cat either. I am going to. remove and test both o2 sensors tomorrow. I'm still puzzles why my motor wiuls only run rich on one side, bank 1. I'm no master mechanic but I'm not a fool either. This is my third Lt1 ta and i learn more wirh each one. Useing logic, i wonder , if an o2 sensor determines air/fuel ratio and there is one for each side of.the motor could a faulty sensor by my demon? Like most parts etc on this car seem original besides any mods.
Another theory abiut my random misfire is soark plug gap.
They were all over .050 and variable. I've herad people running anywhere from .032-.055. I do have NOS but have no plans of running it for a while if ever.
I appreciate any views u may have on this issue
Thanks for tour time
 

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For misfire testing, first check that all plug wires are hooked to the correct cylinders. Last owner might have got a couple mixed up.

Get your plug gaps so all are the same. Then dampen plug wires with a little water and run engine at night where it's good and dark. Look for spark leakage. You'll know it when you see it.

For you fuel mixture, look for exhaust leaks and vacuum leaks. Where intake elbow attaches to throttle body is a prime leak spot. But check all sources. Because throttle body has 2 throttle valves, I believe it is possible to get a vacuum leak there which affects one bank more than the other.

Don't know anything about the obd2 program you have on your phone, but if it does real time running sensor data and logs it to a file that can be reviewed, it's good.

Do a running sensor scan, drive the car under different conditions and see what sensors are doing. If your not familiar with what sensor reading mean, pm me with your e-mail address and I'll send you a pdf file on the subject.

Anyway, check your o2 readings, the 2 front o2's should be jumping around on both sides of the 450mv center point. The 2 back o2's won't switch much as they are there to tell pcm that cats are working. Since you have no cats, they should still read pretty constant.

Also reading your short and long term fuel trims will tell you how rich or lean engine is running. Obd2 cars have readings like -1 or +2 etc.
 

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Discussion Starter #8
I replaced my plugs and wires shortly after i bought the car. I double checked my work today, all wires routed properly, none burnt either. I cleaned and gapped the plugs as well. I'll try the water on wires test tonight.
 

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Discussion Starter #9
Sprayed the wires, nothing. I drove the car to work and back, no misfire. Only a few miles away though. I'll have to a longer drive and see.if the problems return. I'm returning NGK t55 s and gapped them at .042. Also Jegs 8mm wires.
 
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