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I have a 95z28 m6 with Mac midlength headers and 1.6 roller rockers it also has a vented opti. Last week it started missing at low rpms like 2000 to 2500 and more in first gear. And after I installed the headers and roller rockers it would shake and lurch if you put it in 6th and were under 60mph not sure if that's important. I changed the plugs when I installed the headers with ngk and wrapped the wires with heat shield tape. and that was a couple months ago. I also changed the fuel filter as a first attempt when this problem developed. Not sure if I have a wire or if the coil and opti are headed out the door. Any suggestions are appreciated. Thanks Wesley.
How many miles on the car? Any codes? Fuel pressure is good? Double check to make sure the wires aren't hitting anything; what brand opti? How many miles on it? Start small/with the basics then work your way up.
Sorry 98000 on the car not sure on the opti ive had it since 2013 and it was vented when i got it i do believe the water pump drive seal is leaking tho. Haven't check the fuel pressure yet and i was think about changing the wires out since i made the mistake of not changing them when i did the plugs but they look like the originals. I've tried to keep them off the headers but they always seem to creep their way back on to them on the wrapped parts tho.
Sorry 98000 on the car not sure on the opti ive had it since 2013 and it was vented when i got it i do believe the water pump drive seal is leaking tho. Haven't check the fuel pressure yet and i was think about changing the wires out since i made the mistake of not changing them when i did the plugs but they look like the originals. I've tried to keep them off the headers but they always seem to creep their way back on to them on the wrapped parts tho.
I had a misfire like this once because one of my spark plug wires on the PS was getting rubbed and eating through by the belt, just under the a alternator and a little to the right of the AC compressor. Sounds like a opti issue, but could very well be a fuel issue too. Check your wires first and verify fuel psi before going any further.
No. I have not had it tuned with the headers on but it has run fine for the last several months so i wouldnt think thats the problem. How do i go about checking the fuel pressure?
I had a similar issue and it was a cracked spark plug along with a bad rotor.. Eventually my coil went out from over working itself to bridge the gap..
Seems the consensus here is a spark related issue based on combined experience. With the engine running, in the dark, check under the hood for any arcing.
To check fuel pressure, you need to put a fuel pressure gauge on the fuel rail crossover pipe Schrader valve behind the intake manifold.
If the water pump shaft is leaking, that needs to be addressed ASAP, that's probably contributing to the issue if it's leaking coolant all over the opti. The WP has to come off anyway to inspect the opti...
Sounds like spark to me. Some of the bigger aftermarket wires often cause more problems than they solve. LT1 ignitions are fussy about resistance... Do your best to minimize it. 9 times out of 10 a fresh set of delco wires and the right spark plugs gapped conservatively is the miracle cure for these issues. Also use di-electric grease to ensure good conductivity.
Ok y'all. I got my hands on a pressure tester. With the key on engine off I got 35 with the engine on and vacuum hooked up I had 30 and vacuum off and PLUGGED I got 40 both at idle and correct me if I'm wrong isn't it supposed to be 43.5. I also looked for sparking in the dark and didn't see any. I'm gonna get a 2nd set of eyes on it later. I got new plugs from NAPA and was going to put those on when I replace the water pump seals this weekend and check the opti for signs of water on it.
Ok y'all. I got my hands on a pressure tester. With the key on engine off I got 35 with the engine on and vacuum hooked up I had 30 and vacuum off and PLUGGED I got 40 both at idle and correct me if I'm wrong isn't it supposed to be 43.5. I also looked for sparking in the dark and didn't see any. I'm gonna get a 2nd set of eyes on it later. I got new plugs from NAPA and was going to put those on when I replace the water pump seals this weekend and check the opti for signs of water on it.
Thanks
Wesley
Fuel psi needs to be higher. Anything under 39 could point to a bad fuel regulator or pump. It should be 41-48. Did you hit the key more than once on initially checking? It could have gone up more if you hit it twice but still. Sounds like a fuel issue to me. Did you buy the Felpro seal kit? Make sure you buy a twin chisel tip sharpie, hollow out it's guts and make this tool for installing the WPD seal. It's a double lip seal so it's a real pain.
Another thing is if you do replace the timing chain cover gasket DROP THE OIL PAN BEFORE YOU TAKE THE COVER OFF, or your life will suck. Ask me how I know And when your changing the plug wires and plugs do it one at a time so you don't get them crossed or mixed up, as others stated big wires cause more problems than they solve. Stick with factory mm size, and make sure you gap your plugs and put spark plug grease on them so you'll have ease of maintenance next go round. If you need any additional info PM me, I'll be glad to help.
Fuel psi needs to be higher. Anything under 39 could point to a bad fuel regulator or pump. It should be 41-48. Did you hit the key more than once on initially checking? It could have gone up more if you hit it twice but still. Sounds like a fuel issue to me. Did you buy the Felpro seal kit? Make sure you buy a twin chisel tip sharpie, hollow out it's guts and make this tool for installing the WPD seal. It's a double lip seal so it's a real pain.
Another thing is if you do replace the timing chain cover gasket DROP THE OIL PAN BEFORE YOU TAKE THE COVER OFF, or your life will suck. Ask me how I know And when your changing the plug wires and plugs do it one at a time so you don't get them crossed or mixed up, as others stated big wires cause more problems than they solve. Stick with factory mm size, and make sure you gap your plugs and put spark plug grease on them so you'll have ease of maintenance next go round. If you need any additional info PM me, I'll be glad to help.
Wow. Thanks for all that! I hit the key twice on the initial and 35 is what i got. Is their anything i can do to check the regulator or pump to narrow it down. And yes i have the felpro kit but i did did not plan on doing the timing chain cover but im going to take a look at it while im in there and go from there. How did you get around the oil cooler lines to get to the pan bolts?
replacing the TC gasket, unless it CLEARLY is leaking, is not what I would focus on.
the leaking WP drive seal can easily contaminate the Opti causing your problem
your plug wires you say touch the exhaust so you put heat covers on them.....1st run your plug wires exactly like they are stock through all brackets & looms. At this point replace the questionable plug wires
if you can not see every plug boot completely for arcing...you need to do that. This means you need to jack up car on stands and look in the dark VERY carefully for any arcing from plug
your fuel pressure is slightly low. with the gauge on (you need one you can se while driving) do a SUSTAINED WOT hit....does the FP drop. If yes your pump is failing
pull the small vacuum nipple off FPR after the car has run. Is there any sign of fuel in/on it? if yes your FPR is also bad
09-10-2015, 06:23 PM
Low rpm miss. Please help 
And when your changing the plug wires and plugs do it one at a time so you don't get them crossed or mixed up, as others stated big wires cause more problems than they solve. Stick with factory mm size, and make sure you gap your plugs and put spark plug grease on them so you'll have ease of maintenance next go round. If you need any additional info PM me, I'll be glad to help. 
