MarcR94v6

ACdelco opti with maybe 3k miles on it throws me this code and I have it towed from my body shop to JBA Racing shop that built my motor so they can figure out exactly what it is. Assuming it is the opti and not some related electrical or other component, what could have caused this so soon? Maybe I didn't do a good job sealing the waterpump (although no leaks are visible)? I recently replaced the FPR and EGR valve and after the second day, bad stalls and it died twice while I was checking it out under the hood, engine idling.

I have a perfectly good spare NAPA brand opti just in case, but would the whole thing need replaced or just the cap and rotor? And can I make a vented cap out of a 94 opti without changing the timing chain and all that? I don't mean use a 96 opti, I mean just vent the cap of a 94?

Injuneer

The low res pulse is generated by the optical module in the back 1/2 of the Opti, so replacing the cap/rotor will not fix DTC 16. Did you clear the code to see if it came back right away? It isn't unusual to see DTC 16 as a "stored" code. The code can only be caused by the PCM not seeing the low res pulse patterns for 2 revs of the crank. If its an active code, it shuts down the fuel system. Could be the optical module, could be the wiring harness.

MarcR94v6

right now I'm pretty much thinking the waterpump was leaking onto the opti because I re-used it instead of buying a new one and/or I didn't install it well. If thats the case, does that necessarily mean that the opti is fried, can it just dry out?

Also, what do you think about this?

http://www.fierolt1.com/lt1_9394OptiRepair.htm

Injuneer

You have to check the code, while you are trying to start it. First pull the "PCM BAT" fuse for 30 seconds to clear the stored code. Then when you try and start it, see if DTC 16 pops up right away. That will tell you if its not starting because of the optical sensor, or if its not starting because of some other problem. The "other" problem could be in the cap/rotor portion, due to being wet. There is no code set for problems with the high voltage section.

Have you pulled the wires off the Opti and checked the ends of the wires and the Opti cap for corrosion or being wet? Have you checked the Opti harness connector for corrosion or damaged pins?

Adding a vent as outlined in the article you linked will work, and its a good idea. But if the internals of the cap/rotor are damaged - carbon tracking, burned contacts, worn rotor, di-electric failure of the epoxy that seals the internal wiring from the terminals to the wire towers, etc. - you will need to replace the cap/rotor as a minimum.

The key is to figure out whether its the high voltage section or the optical module.

MarcR94v6

I actually dropped it off at the shop to do a full rundown on what the problem is, and they are busy so haven't gotten back to me yet. Based on what they say, I may do it myself or pay them to knock it out. And yes, I would use a new cap regardless, but at this point I'm thinking of just using the vented MSD cap instead of doing all that fabricating to a perfectly good cap.

I'll keep updating when I have news.

MikeGyver

Happened to my buddy a while ago. It was just the foot long wiring harness that connects to the main engine harness at the passenger side of intake manifold and plugs into the distributor.

MarcR94v6

Well they said they are done already, thye just re-did some wires like the maf sensor connector (which I poorly re-did), the coil wires were crimped (which I also re-did when I found the ground cut off but thought I did a good job). I guess I twisted them when I swapped my coils from msd back to stock when I was trying to get it to start better.

It seems a little too easy and I'm not sure I'll feel safe from dieing for a while but then agian, being that the code 16 is intermittent and doesn't stay on, I'd say it may be it. They took it for some test drives and couldn't get the problem to re-occur. If nothing else I can check the opti harness myself, but they probably already did.

MarcR94v6

^^odes this sound possible? I took it home tonight from the shop and I'm not sure if it's running weird or if it's all in my head. So much crap with this car, I'm afraid to drive it to work tomorrow.

EDIT: Ok, it's acting the same as it did before the car would stall and die, only that hasn't happened yet. I start it several times to see if it starts right up, and the first time after sitting for a while it clunks and doesn't start. After a few more tries it idles rough like it used to at first startup and now I'm getting a lot of white smoke.