I have ~500 miles on my new engine. When I built the engine, I installed a new fleabay Opti, new MSD wires, new NGK plugs. Put about 500 fairly easy miles on it getting it broken in, fixing small issues, etc. Then I made one short WOT run, and the engine started to run rough. On the way home (~5 miles) it got worse and worse, at one time dying while decelerating. I parked in the driveway, and when I went to pull it into the garage that evening it started backfiring. The next morning I went to pull it out to work on it, and it was backfiring like crazy and took ~5 minutes to start.
I pulled the Opti, checked and cleaned it. Installed new plugs since the ones in there were jet black. Checked out all the wires. Reinstalled the Opti. Tried to start it, same problem. Took my original GM opti, cleaned and sealed it, installed it, same thing.
It seems to be ignition related, since fuel pressure is good, it's getting lots of air. Spark, fuel, air, right?
Any help would be greatly appreciated.

 

Any codes?

 

No codes were thrown at the time it started backfiring in my garage. I checked using AutoTap, which normally gives me all that set the SES lamp as well as those that do not.
It is possible that something mechanical has occured, slipped timing, bent pushrods, etc. But everything in the engine is new and built to handle 7000+ rpm and 700 rwhp.
Crank position sensor, perhaps? I don't know how to test the coil or the ICM. I checked with shoebox's website, and his examples were completely different for both items.

 

Pulled the fuel rails, no leaks.
Used an inductive timing light, every wire has a hot spark.
Loaded a different s/w load into PCM, no change.
Swapped out PCMs with another 97 OBD2 with an unknown tune, would not start. Had spark, but no backfiring and no spark.
Had battery tested, it checked out fine. Getting ready to:
1) Install OBDI PCM to eliminate Crank Position Sensor as a failure point,
2) Pull out remaining hair in preparation for Halloween.

Anyone know how to test a 96-97 ICM?

 

Crank position sensor has nothing to do with it. Its only there to check for misfires in OBD-II. You can unplug the CKP sensor and the engine will run fine.

Is it possible the rotor came loose in the Opti? Might still fire, but not at the right time.

 

O.K., one less thing to check. When I pulled the fleabay opti, the rotor screws were still loctited in. When I put the original opti back in (the factory GM unit with ~40k on it) I also loctited those screws. While it certainly could be possible, it is most likely improbable.
Would it be possible for me to miss the cam pin each time when I installed the opti? I lined it up per the book when I built the engine, and then by sight when I have installed the opti each time after (twice). I check the back of the opti each time, and it is flush with the block. Is there any other way I can verify this?
Thanks.

 

If it ran OK for 500 miles, and then started running poorly, its not because you indexed the cam dowel pin incorrectly. It wouldn't have run that way. A 120* cam error (wrong hole) is a 240* crank error. The vented Opti's are not like the unvented with the spline drive, where you can be off by one tooth, and still have it run, but not well.

Is it possible the dowel pin is too short and came out of the Opti?

 

Certainly, we both know anything is possible. (Just look who has been "leading" our country for the last two decades. ) How would I check the dowel pin? I have a depth gauge in my dial caliper, so I can remove the current opti and see how far the pin is protruding. Hopefully there is a spec?
I just checked the back of the fleabay opti that I installed originally, there were no scratch marks indicating that it was spinning freely against the tip of the dowel pin.
I am looking at my copy of Mavrigian's How To Rebuild...LT-1...Engines. I installed the fleabay opti in exact accordance with his instructions and pictures, so I am confident that was correct. If ithe pin slipped up into the cam and was not protruding enough to catch the opti gear, well, all bets are off.