not sure if i should post this over here or not, i havent gotten it figure out yet.

i have a 94 lt1, and i've had a high rpm miss for a while now
here is what it looks like on the dyno
http://www.mofbody.com/blkchevyz/webdocs/dynosmall.jpg
it basicly feels like the car shuts off for a second then gets right back in it.

i've changed everything i can think of to fix it and still no luck...
im sure i'm forgetting something but here is my list of stuff i changed.
3 opti
3 sets of plugs and wires
2 coil/ ignition module
2 ignition boxes, and ran with out one
new fuel pump
2 valve springs kmotions and comp cams
added a second ground to the car.
hell i just changed cams too, i was running the 306 cam now running a fms cam.

the rev limiter for the computer is set at 7 k, and i've moved my ignitions boxes up to 7 also
i've done alot of scans with datamaster and all i see is a drop in rpms
here the recording of the dyno run
http://www.mofbody.com/blkchevyz/webdocs/chris1.uni

also i've messed with the timing to see if it had to much advance in it and it still missed...

is their a way to figure out what cylinder is missing?


i want to run nitrous next summer so i want to get this fixed... any ideas?
im getting tired of just throwing money at it and not getting anywhere

 

It could be your opti ...

 

i've put 3 different ones on so i dont think its the problem

 

Have you flow tested your injectors... what is the wide band 02sensor telling you when the car is missing?

THX Jim

 

never mind i am a dope today i just opened up your dyno graph

 

no i havent flow tested the injectors, i did put my factory ones back in and it still missed with them in.


the air fuel ratio doesnt change really, at least it didnt on the dyno, but that was pluged into the exhaust tip so it might be to far back to notice...

 

I had the same thing kinda going on...turned out to be my fuel pressure regulator. Easy to check if you have your old stock one around.

 

well i have an slp one that you have to chop up your factory one.
but im sure i can find someone local to let me borrow their.

 

any other ideas?

 

If you post your data log as a ".csv" format file, those of us without DataMaster can look at it. Use the "export as .csv" option in DataMaster. Was there any evidence of a sudden drop in injector PW at the time of the "shut off"? I had a problem with something like that... the engine would just shut down for an instant.... "Bang"... and the pulse widths would drop to "0". But I was running an ignition system that was only using the Opti optical sensor.

Have you checked the wiring for possible interfernce of signals from a high voltage line (e.g. plug wire) too close to, and possibly running in parallel with the harness for the Opti?

 

http://www.mofbody.com/blkchevyz/chris.csv
here it is in a csv file. as you can see the injector pulse width doesnt drop at all.


the only thing the plug wires are touching are other plug wires.

 

Look at the right O2 sensor... when you get into trouble it has dropped 50-90mV below the left O2. It happens quite a bit earlier too, but intermittently. Look at frames 2027, 2029, 2044, 2057, 2061, most frames after 2070. Your pulse widths are identical, but the mix seems to be lean on the right side at times. I know the stock narrow-band sensors aren't all that accurate, but it seems odd that much of the time the left and right sides are very close, and then as RPM goes up the difference becomes larger intermittently. When you are WOT, the right O2 is on an average 38mV lower than the left. The range of mV values is 40mV on the left during that time, while the right side varies over a range of 68mV.

Which side did they put the wide-band in?

 

i noticed that, but i just figured it was because of the different locations of the o2 sensors.

that wide band was put into the tail pipe...
since then i added a couple o2 bungs and i have a hand held wide band that i've been running on the driver side of the motor... i havent hooked it up on the passanger side yet.