Hello all, I am a mechanic and have been for over 40 years. I usually work on foriegn stuff but thought I would help a buddy. I am working on a friends 95 Z and have ran into some problems. First It has a code 29. I have read about the air pump and we live in a area that we will have to make it work because of emissions tests here. I am sure I can get that part done. The biggest problem is that It had a MSD Opti Spark distributor on it. He took it to a shop that told him that it was bad because it would intermittantly not start or die. I am not familiar with this system. He went and got a new (generic brand)distributor and called me up. I went over and installed it. NO Problem. Yea right! I noticed when installing it that the rotor on the new distributor was facing a different direction than the MSD was. The distributor only goes on one way because of the fit on the front of the camshaft with the three bolts and the tang sticking out. I informed him of the problem and that I didn't think It would run correctly. It is off what would be about 2 teeth on a conventional distributor. He told me that he had read about them and that it would set it's own timing with the computer. I said "OK" and installed it. Well come to find out it runs like crap and is not setting it's own timing. My question is there more than one firing order or is there more than one distributor for these that would put the rotor the equivilant of 2 teeth clockwise (looking at the front of the engine)? Is there any way to set the timing on these systems that will make that much of a change? Any suggestions here. I know you people are more familiar with these systems than I am so I am asking for suggestions. Thank you in advance for any information.

 

If the pin is installed in the correct slot on the drive of the opti (the cloverleaf looking thing) then the opti is indexed correctly. Timing is 100% controlled by the PCM (unless the "timing screw" on the MSD has been toyed with).

Have you checked for spark out of the opti? Check the harness connections on the opti and the coil wiring.

There are several other tests you can do on this page shbox.com to determine just about any ignition problem. That's where I would start.

 

Some opti's have pin drive(95 and up) 94,93 have spline drive. The opti can be installed wrong on either drive system if you are not careful. In general, anything other than a GM or ACDelco opti is a bad idea(other are simply not as reliable). There is no timing adjustment. Computer(PCM) controls 100% of it.

Watch this video....very good stuff.
Buick Know How: LT1 Optispark (ABITS) Distributor Operation and Diagnostics - YouTube

I think this has the same links that RamAirTA just posted, but this is the opti sticky at the top of the forum.
https://www.camaroz28.com/forums/lt1...d-opti-601565/

 

DTC 29 generally indicates the fuse for the AIR pump is blown. Replace the fuse and if it continues to blow the pump is probably seized up and pulling excessive amps. You can eliminate the problem by unplugging the pump and then replacing the fuse. Leave the pump unplugged. It only runs for a couple minutes at startup to help the cat heat up faster. It would be unusual for an emissions test to pick up the fact the pump is not working because the tests are usually run with the engine at full operating temp, with the computer in closed loop. The pump would not be operating under those conditions.

If you feel you have to have a running pump, the are lots of used ones that people have removed. Or, there is an AIR pump factory recall that repairs the problem. Not sure if the dealer would still honor that.

 

If you look at this diagram from Shoe,
http://shbox.com/1/opti_back.jpg
and you have the drive mechanism in the same place on both distributors but the rotor is pointing in different locations, that is obviously a problem. A PCM/ECM can not compensate for a miss assembled rotor.

The PCM can retard or advance the spark initiated at the ICM but can not alter the physical location of the rotor relative to the cam.

No engine can have more than one firing order at the same time.
SBC previous to LS had a different order than LS.