black95z28vert

Hi all, My sister has a 95 triple black z28, 6 speed, vert with 45000 miles that she bought brand new, and it has a horrible miss while driving. its fairly intermittant, but once it starts, it gets worse and it will damn near knock you out of your seat. no specific rpm range. we replaced all 8 plugs, coil, ign ctrl module, plug wires, fuel system is clean, new pump, sock, filter, injectors all checked, getting steady stream of fuel. no codes, no check engine lights. I really wanna help her with this. shes done so much for me. shes gonna pay for my tuition, got me a cell phone on her plan and paid off my car so i can keep just a p/t job and go to school f/t, and i get a ws6 trans am 6 spd when i graduate. so if i can fix her baby, it would mean alot to me. thanks guys

dookie454

U probably have moisture in the Opti. Either replace it or first try to find the "RESTRICTOR" in the vacuum line and remove it completly. This will force more airflow thru the Opti, and possibly dry it out.

The problem is all with the Opti High Voltage side itself, the contributing factor is the low mileage of the car since the moisture gets in there and cant escape, with low miles it sits in there a long time messing everything up. Alot of times WASHING the car is all it takes to place the moisture in there. The heat of the engine probably makes steam/fog/condensation within the opti which is probably why it gets worse since the ignition is basically misfiring at this point.

You could also do what I used to do which is park the car while running for 15-20mins once it starts happening, but you have to remove the "RESTRICTOR" to get the best results (this will help pull the moisture out of the OPti, if it exsists.


BTW, your not getting any codes because everything is actually working OK (PCM is sending and receiving spark and timing signals ok, just the spark is not being routed to the proper cylinder at the right time since it's shorting out either due to moisture or a rusted/busted rotor in the Opti but the PCM doesnt check if the spark plugs get the signal or not... dumb.. imagine that code.. "Cyl 4 is not receiving spark and is causing a missfire").

Starting 1996 and newer (OBDII) Missfire Detection would give you a blinking Check Engine light and even which cylinder is missfiring if it is somewhat consistent, but wont tell you why. This combined with the horrible miss will surely concern you, but still it wont tell you the OPTI is wet

black95z28vert

where would i find the restrictor? ive heard nothing but bad about that optispark crap.

dookie454

If you get under the car find the Opti behind the balancer, there's two vacuum hoses attached, one has a simple little block in it which looks like a small check valve towards the top near the intake. Take it out but re-connect the vacuum hose becuase you want the engine vacuum to pull alot of air thru it.

Keep in mind it's probably pretty messed up in there since it's low mileage and the water's been in there awhile, plus if it's cold outside the cold air with the hot OPti could actually make more moisture... I've only done this in the summer.

black95z28vert

appreciate it man. gonna give er a try in the morning. will post results

dbrunner2

Be careful with removing the restrictor. I tried that once on my MSD opti (their replacement for the 93-94 cars that includes a vent) and it ended up with oil inside; apparently the seal where the opti driveshaft enters the motor and plugs into the cam couldn't take the pressure differential that resulted from more vacuum reaching the opti and oil started passing through. I haven't had any experience with the different seal that went with the new drive design on the 95 and up motors, so you might be OK; I'd recommend against leaving the restrictor out long term though, just in case. While you're down there, also check for any problems with the line that feeds filtered air TO the optispark from the intake; if that is broken you'll be sucking water right in every time it's wet out.

Fatdog2

Do live in a cold area?You might have condensation build up in the tank(water).Does she keep the tank full always?Might check for the gas cap tight.My02.

black95z28vert

i havent had a chance to even try the opti fix yet. been busy with my own stuff. but i will try the gas cap thing first