I have searched for opti problems but don't seem to find one quite like mine. My car never dies and never have trouble starting but... I seem to be having some trouble when it heats up. Depending on the temp outside I can drive for 10 miles or maybe longer if it is cold before the car starts popping and will not rev over about 1500 rpm. All the while sputtering and backfiring and if I give about 1/2 or more throttle it knocks really badly. This is a new engine and yes I'm dumb as I blocked off the vent lines while I waited for the vacuum lines to arrive. This was a last minute change to go to the vented versus the non vented. Could blocking off the vent lines kill the opti? I have the correct harness now and have run the car for weeks hoping maybe it was moisture that would eventually get vented out? When I get the car to the temp that it does this, I can kill the engine and if I let it sit for maybe 10-15 minutes I can drive for another mile or 2. If I let it sit for and hour or so I can drive for around 5 miles. If it completely cools down, I can drive for 15 or so miles again depending on the temp outside. Sorry for the loooong post Thank you for all your help...ohh and this is my first post

 

Hey I just registerd on this site a few minutes ago but anyway.
I dont think blocking the vent lines would cause it.I had 93 Z had same problems fine until it gets hot I've spent too much money on these things where did u get the motor I've bought brand new one's that were bad..

Hope this helps.

 

There are 100's of stories on here that the car only does this when hot. Only a few have the running problems your describing. I can't remember all the things to check but you will find endless links on this matter.

 

I would get the vent line hooked up as soon as possible. With that line disconnected, it can lead to premature opti-failure. I would start off easy and put a fuel pressure gauge on there and see what the fuel pressure is doing when all of these problems are going on. If the pressure looks good, then I would move on to the ignition and start troubleshooting there.