The Bank 2 LTFT average indicates it's running lean (14%) in general (all fuel trim cells) on Bank 2 but more severely lean (24%) in the idle cell (16).

The pre-cat O2 sensor readings are useless in screen shots. If heated up hot enough (600°F) to operate, and with the PCM in closed loop (indicated in a screen shot), they would be cycling rapidly (~9 time/second) over a range of less than 100mV to more than 900mV.

MAP is high. Would expect about 18-20”Hg vacuum at idle with a 29.5”Hg barometer. Yours is 15.6”Hg….. too low. For calculation purposes, vacuum = MAP minus Barometer.

Problem on Bank 2 could be a vacuum leak, misfire, valve adjustment, plugged injector, exhaust leak before the pre-cat O2 sensor.

MAF is 9.0 grams/second, but the indicated scanner units of 0.02 lb/s doesn’t contain enough significant figures to be meaningful. Never seen a scan with lb/sec, usually grams/sec or lb/minute.

 

If he's got a hotcam clone, 16ish vacuum might be right for it. I think my vacuum is around 15-16 for my CC503. I'll see if I can fire it up this weekend to check.

OP, can you link us the cam you installed in it?

 

But he’s running 1.5X rockers, which should reduce overlap.

 

Thanks Fred.
What vacuum leaks could only affect one side?
I have the valves set at zero plus 1.25 turns, but the stumble occurs when I accidentally had it at .25 turns.


Here's the cam.
https://www.jegs.com/i/JEGS/555/200500/10002/-1

 

Injector o-rings, intake manifold gasket

Shoebox’s valve adjustment guide:

4th Gen LT1 F-body Tech Articles

 

10-4 on that(overlap or lift?), I did miss the 1.5 ratio on the rockers. He mentioned stock except for the long tubes/Y pipe and it still didn't register with me.

The cam he linked looks less aggressive than the CC503 as well, so I agree he should have more vacuum than my setup. Looks like Jegs spec'd it 1.6 ratio, so his lift will be 0.492 on both I/E if I got math right.

 

I asked about the valve train. All that was changed was the cam. Pushrod length? Coil bind? Might explain issues with valve adjustment.

 

Its been a long time since I've messed with one of these but can you have the Opti installed 1 hole off?

 

Well, I think I found my misfire on #5!

 

Didn't the previous owner tell you he replaced the plug wires (among other ignition parts) in order to eliminate the "stumble", but it didn't help. That wire doesn't look very new.

 

Yes. On a vented Opti, if the cam dowel pin is too short, or if it gets pushed deeper into the cam by pulling the Opti down with the mounting bolts when it resists seating, it can slip out of the single index hole, and get caught in one of the "cloverleaf holes". You can detect this misalignment (1996/97) with an OBD-2 scanner that can read "CKP:LoResAngle" (e.g. - Tech-2). That is a measure of the angular difference between the crankshaft position angle and the Opti low res position angle. If that number gets big enough, should set P0335 or P0336.

http://shbox.com/1/opti_back.jpg

 

I think it is "newer", but that end was resting on a header primary. The plug was wrapped in a heat sock, and it still burned through. I changed out the wire from a spare set, and rerouted it away from heat. I also swapped the Denso O2s for the Delco O2s.

I took the car out and it idles much better, but still breaks up at low rpms. I unhooked the battery to reset the fuel trims, but they still maxed out on bank 2, so there is still that mystery to sort out.

I did get a more detailed scanner, so hopefully get more meaningful data:


Limited-time deal: TOPDON TopScan OBD2 Scanner Bluetooth, Bi-Directional Scanner Wireless All System Diagnostic Tool for iOS & Android, 8+ Hot Reset, Repair Guides, Check Engine Car Code Reader, Performance Test https://a.co/d/dHWPDsA

 

Without rereading all of the above, are you still running the sellers home-made O2 sensor extensions?

 

I might be wrong, but I don't think the above can log the car to a .csv file.

I think you are going to have to get something that can log to a .csv file. There not as many good options to log an '96/97 LT1 OBDII system as there used to be. I've been looking around at the various options and I think the most cost effective one might be this one......


You'll need a laptop to log the car. The software that comes with it does have the options for GM enhanced parameters for around an additional $44, but I don't know how many additional options you'd get.

I plan to grab this thing and have a look at it, as I've not had a really good option to suggest for '96/97 OBDII scanning since autotap shut down. It was not perfect, but was good for the money.

For viewing the log, I do like MegaLogViewHD. CSV files can be massaged and imported to get a good graphical view of what the parameters are doing over time. Looking at point values on a scanner don't get you the full picture of what's going on. In the right hands, the couple of graphs they can display at one time may be enough to diagnose the car, but I prefer being able to look at more parameters at one time.

You can try it for free.
https://www.efianalytics.com/MegaLogViewerHD/

 

No, I read that the O2s are sensitive to wiring changes, so I bought these:

Michigan Motorsports 02 o2 Oxygen...