Mike94transam

I realize that this comes up so often but after hours and hours of reading similar posts I am still coming up short. I have a 94 trans am, stock except for fipk and cat delete. It has 60000 miles. I replaced the opti with a API unit because it was working real crappy in the rain. After putting the new one on it was difficult to start and was dragging the starter. Broke nose cone on starter - shop said that timing must be too far advanced and engine was turning starter backwards(fighting against starter) during starting. replaced starter and put new guts in opti, this time brand new from Carquest and after about 10 starts broke a second nose cone off. when I do get it running it will stall randomly as in sitting idling perfectly for 10 min then stall and also running at a steady 75mph perfectly and then stalling. No stumble or hesitation before stalling, just as if you turned the key off. No codes are showing. replaced ignition coil, no effect. replaced ignition module, no effect. Brought it to another shop and they are saying that high and low resolution signal wires are showing around 9v, unplug distributer and they read 5 v. Please tell me I don't have to buy a third opti......how can they both be bad????? Going crazy here, and broke, any thoughts?

Guest47904

Either the second shop is idiots or you misinterpreted what they told you.
There can be no voltage from the distributor when it's unplugged. 12 volts and ground go in. 2 square waves from 0 to 5 volts comes out at differing frequencies. When either 12 volts or ground goes away. So do the 2 square waves. Of course when the engine is not rotating, the 2 square waves could be at 0 or 5 volts. Depending on where the shutter wheel in the distributor lands at the optical sensors.

As far as timing is concerned. The only way to get it off is to install the opti wrong. That is nearly impossible. Although it seems every week someone else does it. I always recommend that it be installed with the cap off. You should know which cylinder is at TDC. The rotor should be pointing in the direction of where that cylinders contact was when the cap was on.

The number one reason nose cones get blown off is misfires while cranking. My L31 did it with a bad cap and rotor. But there are other reasons from an ignition stand point it could do it. If you have sooted up spark plugs from having been run rich. Bad or burned plug wires will do it.

There are other reasons to have a nose cone blow off. Not having it shimmed properly. Or bad injectors that are flooding a cylinder. Or not even flooding but dumping a lot more fuel than normal.

You need to not bother with the shops you been messing with.

I also suggest you test the opti and confirm it's installed correctly by use of the rotor direction toward the cylinder at TDC.

Then start checking for spark first at the coil then the plug wires. ALL BEFORE YOU ATTEMPT TO EVEN START IT AGAIN.

Mike94transam

Thanks for some ideas. I did have the keyed spline verified that it went in the proper way so I'm pretty sure that part is okay. I put new plugs and wires on during the first opti install. The random stalling part is also throwing me for a loop, not sure how that fits in. Also it does spark knock during low rpm load but seems to idle perfectly until it stalls.

Guest47904

If your KS and PCM are working like they should that is impossible. Unless what you hear is the engine trying to run at a such a low rpm before it shuts off. Like the old carbureted engines did when they wouldn't shut down from Dieseling.

Injuneer

If the splined shaft is off by 1 tooth, thats 20 cam degrees, or 40 crank degrees. If it was advanced, that would make it hard to start, probably fight the starter, and would cause so much spark knock that the PCM would not be able to retard the timing enough to stop the knock (15-deg stock limit on retard).

When you say you put "new guts" in the Opti, what EXACTLY did you change? The rotor?

I'd still bet the splined shaft is not indexed correctly.

Mike94transam

The spark knock isn't before the car stalls, it is during acceleration mostly when in 2nd gear(automatic) going on a highway onramp accelerating modestly. And the guts were Cap, rotor, optical wheel. When the second opti was put in I specifically told them to try the spline 1 spot over both ways and they said they tried and it only slid in good in 1 spot. I didn't witness it so I am trying to take their word for it.

Injuneer

Still confusing. You mention various parts as "guts". Then you mention a "second opti". Why would they have to remove the opti if they were only replacing the internals.

And yes, spark knock is most likely to show up when accelerating, particularly if there is too mech advance. At low throttle positions, lugging the engine to accel, it's likely for knock to show up, particularly if the EGR system isn't functioning.

In addition to indexing the splined shaft incorrectly with the cam sprocket, it also has to be indexed correctly to the back of the opti.

Mike94transam

Update:
I said the heck with it and bought an AC Delco opti from Summit Racing and it worked!! I asked the mech if he noticed if the old one looked as if it was installed incorrectly and he said it looked fine. Main thing is I'm back on the road, even though half the season is gone, the only thing left to do is try and get a refund from the latest opti purchase. The first one was from AIP, their brand, and the second was from CarQuest.