Listen my 96 Z28, has developed a mis-fire. Now I changed the plugs, and wires withing the last.... 20,000 miles (thats how long I've owned it)... while ideling today after court, the car made a couple backfires, and shook, then the low oil light came on... (I shut the car off) and the light went out... I know those sensors go bad... so Im not really worried about the oil. and my oil pressure was arount 10-20lbs idle (normal for an LT1)... I stopped at Knopps, and hooked the scanner up to it, and it has a serious history of mis-fires... but nothing current, (even with the car shaking and acting up) The plugs are such a pain in these cars... so I wanted to see if anyone else had the same kind of issues.... Also got a code for an O2 sensor (post cat).. so that should not effect how the car is running.... didnt know if I should still go old school and pull all the plugs and wires, or if I should put a new OPTI-SPARK in it, since I think its the original one with 140,000 miles on it. A little advise would be helpful.. since I bought my girl a 95 Z28, and I can t have hers being faster than mine...
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Somethings making it misfire, and it could be fuel, ignition or mechanical issues (lifters, valves, etc.). If they were able to pull the misfire count by individual cylinder, they must have been using an "enhanced parameters" scanner. The misfire history may point to one or more cylinders misfiring more than others. Have them reset the misfire history and then check it for new data.
I wouldn't jump to the conclusion that its the Opti, without checking the other possible causes. Maybe the cat that set the O2 sensor code had a meltdown and its plugged up, making the engine run poorly. You need to check the fuel pressure. Pop the hood in the dark and look for arcing wires or coil.
Just about anything that could cause it to run poorly should show up as a code, except the high voltage side of the ignition, and the misfires should be incrementing the misfire count.Fred
381ci all-forged stroker - 10.8:1 - CNC LT4 heads/intake - CC solid roller - MoTeC engine management - 8 LS1 coils - 58mm TB - 78# injectors - 300-shot dry nitrous - TH400 - Gear Vendor O/D - Strange 12-bolt - 4.11's - AS&M headers - duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP/800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117MPH straight motor -
If you have 140K miles on the stock optispark, you can figure that it's on it's last legs. Many times the misfire doesn't even throw a code. You might want to try an old fashioned inductive timing light. Clip it on the coil wire and make sure you get a constant hot spark. Do the same for each individual spark plug wire and you might find a random misfire that way.Originally posted by popo8
I still vote for opticus degradus.
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Like Fred mentioned, if they were able to view the misfire history, then they were likely using a GM enhanced parameters scanner. I would take note of the number of misfires on each cylinder then clear the misfire history and then look at it in real time.
Also look for consistent and numerous 02 sensor crosscounts, LTFT's within normal range, o2 sensor voltage switching within normal range, etc., etc.. There is so much to look at and analyze.
Were there any other active or set codes?Comment
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I will forward a link to this site to my mechanic/friend so he can read your advise. Tonight we cleared the history, and hooked the "brick" (scanner) back up and took the car for a drive... it was all over the place with mis fires.... 1 &7 then 2& 8... every possible option.... does that help out at all. They are guessing the OPTI.
My cats were replaced about a year and a half ago with high flo cats.... do you really think they could clog up so quick???Comment
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checked fuel pressure today... GOOD... ordered a new GM opti from a guy on the camaro site... new in the box, GM, $215 shipped. Could not beat the price....Comment
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