hey guys i dont know if you remember my previous posts a while back about the possible opti problems about my 94 z. well i had it scanned and both o2's were running lean on both banks. well i replaced the fuel pump and it runs the same, well maybe a hair better. it has surging, if i gun it it starts banging out pretty bad and wont go over 3500-4k rpm. the warmer the motor gets the crappier it runs. does it sound like my opti spark is bad. it drives to the point to where if i do want to accelerate i have to maybe give it 1/8th throttle to move normal. sometimes it runs good as long as i dont go past 1/2 throttle and other times is runs like ****. the car is stock except for a cat delete and blowmaster. it has 144k.

 

It sounds like it coul be the engine temp sensor that is up by the water pump. This feeed to the ECM and is a lot cheaper and easier to replace that the opti or wires. Also the wire that connects it can be lose or decayed.

 

would the engine temp sensor cause it to run that bad?

 

If the coolant temp sensor is giving the PCM incorrect data (e.g. false low temp), it is possible the engine would run bad when hot.

Have you checked the IC module? They heat soak from being bolted directly to the driver's side head.

 

What about the plugs? Have you pulled them to read 'em? I know its a huge PITA but it might be worth it, especially if they are old. If you haven't done a tune up in some time, I'd start there. It can't hurt. By tune up I mean plugs/wires/coil/oil change/fuel filter. I know the oil probably won'e cause this but if you are already getting dirty, might as well go all the way. Did you check fuel pressure? Should be around 42-47 psi with the vacuum line disconnected. Try looking at the plug wires at night and see if they are arcing around. have you scanned it? is it throwing a code? Personally, I'd start simple with a tune-up (if you haven't already) and go from there.

 

Havent checked the module yet but even when its cold it runs real rough, just runs worse as it warms up. fuel pressure is good. My local friends who are mechanics believe the opti is bad or going bad. if there is a time it runs half decent it runs ok as long as its 1/4 throttle. I wanted to get the opinions of some of the guys here like injuneer and so forth because I know you guys are intelligent about these lt1 motors from what I've read these past few months. Also it takes forever to turn on whenver you use it but if it sits overnight it starts up well. in the morning i turn the key and let it prime then turn it on and bam its on but if i drive it for a second after that and turn it on it takes quite a few seconds to turn on if i let it prime. if i just turn the key it still takes a while to turn on but you can here it kinda turn on if i dont let the pump prime after i've been using the car. hard to explain. I do plan on doing a full tune up but want to see if i should change out the opti.

 

Sounds like you MIGHT have two issues going on. The opti could be bad, or you could have a coil that is getting bad as it heats up. Did you get any codes scanning? If so, I would pull the PCM BAT fuse for 30s, then see if the codes come back. If there's nothing for the opti, then I might test the coil or look for arcing down there. At 144k, what have you replaced regarding the ignition system? Again, this is all kind of pointless if your wires and plugs are bad.

As far as it running worse when warm, I'm going to call Ditto with Fred and Maddog. It really sounds like you have two things going on at once here.

 

the whole ignition system is stock, i've been so busy that i havent been able to check little things. but i'm off for a few days so i want to get it running correctly. it pretty much runs like crap 90% of the time from cold start to operating temperature. I had it scanned but nothing spark or electrical related came up, only the o2's came up reading lean