Over the winter I rebuilt my LT1. It's a stock rebuild with CC503 cam and 1.52 rockers. The motor ran fine before my rebuild, just had low oil pressure due to worn cam bearings. After the rebuild, the engine started right up, ran great with no problems. The only thing that I noticed was that it smelled like it was running rich at idle. Drove it and it drove fine till I would come to stop, then the idle would drop to about 4-500 rpm's and then clean out and jump back up to 900 rpms's. It also would stall out at times. It also set the check engine light on with DTC P0336, crank sensor. I found this odd since I replace the sensor when I rebuilt the engine because it ended up being broken. I sent my PCM out to PCMforless to get programed for the cam change. I got it back and it still was acting up so I took it for a 10 mile run on the Highway. Well that did it some good because the idle problem went away and was running fine. It still has the smell of running rich at idle but clears up in the upper RPM. Well the A-hole came out in me and I got on it pretty good a few days later, the problems came back and now when I go to start it, the check engine light is always on, even after I clear it. DTC P0336 is the only code that comes up. It also loads up on fuel when it first starts and I have to bring the RPM's up just to clear it out. Now I've done some searching on DTC P0336 and came up with my Opti being bad. The crank sensor and the opti are not within the same values as each other. This is why this codes comes up. Yes it is the OEM(?) Opti on the LT1, it looked oem buy the ammount of grim that was one. I did end up cleaning it with degreaser sprayed on a rag. It has 101k on it. I'm thinking that it's going bad.What do you guys think?

 

I think a lot of people would **** themselves with joy if their optis lasted 101k...


Mine started dying around 60k

Since you've already replaced the crank sensor I would put one on it. Its days are numbered anyway and that's probably going to fix your issues.

 

If you can, try this simple test. http://shbox.com/1/4th_gen_tech2.html#opti_test I'd always test your wiring and connections before shelling out for new parts. When my car was running rich it turned out to be the $20 coolant temperature sensor was off. Here's how to test that is you have an ohmmeter http://shbox.com/1/4th_gen_tech2.html#ect

 

That's the code I got before my opti kicked the bucket... It never really died, but when I opened it up, one of the rotor pointer rivets was toast.

My factory opti lasted 140k, and I've heard of others lasting longer. The opti can be a pretty reliable part, at least it has been for me. Just get a new OEM unit and thread lock the rotor screws. That's what I did and my replacement opti has seen 30k miles without a problem.

 

Hmmm Mine lasted till 100k and only died then cause i soaked it at the car wash

 

this is an old thread.. did you ever get the problem resolved smb? was it the opti?