Hopefully someone will be able to make heads from tails on this for me. I've got my LT1 that has run fine for the last 2 years in my Trans Am, and now as soon as it hits open loop, she just dies like I turn the key off. She will immediately start back up with the turn of the key, but unless I'm driving down the road, she will not stay running. A little back story...

I've had my 88 Trans Am now for I believe 5 years, two years in the making, one year with the crappy 305/t5 combo, and the last 2 years in full LT1/T56 trim. I had replaced 99% of sensors in my rebuild of the motor before dropping it in, but did not replace the Opti. Half way through the first year in LT1 trim, I got the deadly Opti codes, which prompted me to get a reman lifetime unit from advance auto, and I just happened to have an MSD opti cap laying around, not that it's relavant, but I used it. I left the unit without a rotor and sealed it really well with RTV sealant. From there I installed the LTCC unit along with 8 coils and made my own wires to the plugs. Everything ran beautifully and so much smoother IMO.

That brings us to the end of the summer last year, day I was going to be taking this vehicle off the road, she starts to just cut out. Now I'm doing 60 mph, so the vehicle would just lose all power, lose a little speed, and then 2 seconds later kick back on full strength and drive off again (because I was in gear and it would "pop start"). I managed to get the vehicle to storage where she spent the winter. Got her out recently, brought her back to my house, and got the same little cut out on the way but shut it down and left it till now that I finally have free time to figure this thing out.

I have attatched the data log I just took, and from the looks of my amateur eyes, I cannot see anything strikingly out of place. As far as programing, I haven't changed much except tire size, and disabiling VATS and any automatic transmission codes so they would stop popping up with my T56 installed and so it would idle correctly. I'm not running A/C, as far as the LTCC unit, she is working perfectly, as soon as it starts up, solid green light from the unit and the red error indicator light does not come on, which means it's getting signal from the OPTI, and the only time the light goes off is when the engine just cuts off. I have watched it on my laptop, and with free scan, and the second the light for closed loop goes out, so does the engine. Need help, let me know what I can do. I've got full diagnostic tools, sensor tester, fuel pressure tester, ect ect, I just don't know where to go first with no ICM to blame it on. And for what it may help, I'm running OBD1 on this.

I attatched a zip file because everything else was too big or the wrong file size, the file itself should open up in excel. If anyone else uses .txt or anything special I can try and convert it. Any and all help would be greatly appreciated, and will try any idea at this point. Also, if there is a more thorough way to collect data, I'd be interested to know how and do just that. Thanks in advance!

 

It might be the O2's or the coolant temp sensor in the water pump.

 

any ideas or anyone that knows data logs can take a look at mine and see if they see something out of place?

Sorry, didn't update the page as it was up for a while. As far as the 02s, what I don't get is watching the vehicle run on freescan, i could see them hopping around like a jack rabbit, but on the data log, its smooth transitions, barely any jumping, and the only movement is on the driver side because it has an exhaust leak at the manifold, because I haven't changed that gasket yet.

What is weird to me, they are both heated o2 sensors, and until cells G/H690, both sensors are really up high, from there the left one breaks off and starts dropping, and around cell H742, the right side starts to drop down, and from there starts jumping around. Left side is always a little less than the right again because of the leak, but why the sudden drop so late like that? And even at that point, if they were clogged if you will, and they open up that late and start working, and if they are working around time of switching to open loop, why would it just die?

And i've heard of LT1 CTS problems, but my temp sensor is reading steady for whats happening, building up as it heats up, and takes a few minutes when it does to cool back down. There is no break in the data reported to the ECU. Also, that temp is in *C.

 

why is it even going to open loop? once you reach temp and are in closed loop it should stay there unless your in PE

im not sure I understand what you did with the coils and the ltcc unit is about.. must be some type of coil conversion like a 411 swap??



I cant view your log

 

Ltcc unit uses opti for the cam/crank position sensor, and uses 8 ls1 coils to run the igniting, bypassing the ozone gases and some issues of the opti.

I mixed my wording, it runs open loop to warm up, and the second it hits closed loop, it shuts down. While monitoring the stats on freescan, I can't watch the light on meaning its in open loop, and the second the light goes out (switching to closed loop) it will die. I can restart the car immediately as long as it runs open loop.