camZ2894

I have a '94 Z28 and having a problem with the LTCC install. I bought the car last march and it was shutting off when I drove it. We took it to a shop that concluded it was the opti sensor so we replaced the opti and installed the LTCC conversion. It was running fine but it had a slight miss, and was not shutting off. I drove it for about a month and then it started running very rough. I took it back to the shop and they said there was a wire that was loose. He fixed it and then shortly after it started shutting off when I was driving it, both at idle and under acceleration. It would backfire pretty badly too which ruined the catalytic converter. Before we did the conversion it was not backfiring when it would shut off. I then took it to a different shop, community auto, and they found that codes 1, 3, and 4 were coming up. This is what the tech has emailed Bob, in which Bob has not been getting back to us...

"Another shop originally installed the modification, this morning as we attempted to start the vehicle it would only turn over. Attached a scanner to monitor data stream and it fired right up. no codes. Allowed car to idle for a minute or two and it shut off, green lite off, red flashing code 1. Last week we found and repaired ground wires to pcm on left head. Car ran but had red lite blinking a code 3. We weren't sure if it would cause a problem, the car seemed to run nomally then. I've scoped hi and lo resolution signals and they seem normal. So far I have seen codes 1,3,4 at different times."

"it would be helpful to have a wiring schematic, this car has a new optispark unit so i doubt the disc is in wrong. it runs good for long periods then stalls or backfires as if the firing order is wrong, then restarts and seems ok. is there some way to scope ignition pattern to see if we are out of sequence when this happens?"

Any info anybody has on a wiring schematic? I have now been without a car for a month and can't get any info from anybody on what the problem could be.

David94TA

I'm no expert but I'll put my .02 cents worth in. Maybe someone more knowledgeable will chime in.

You state that there were problems before the opti swap. The LTCC was installed at the same time that the new opti was installed. Changing two things at the same time is generally not a good idea. I see the reasoning if you have to have a shop doing the work, but still not the best idea.

To me it sounds like you still have either a bad ground, a hot wire that is getting grounded or maybe just a bad connection somewhere. If they haven't already, get them to check the harness going to the opti.

As much of a pain as it would be, I would probably put everything back to stock configuration to see if the problem is still there. If the problems are still there, you know that it is not the LTCC.

I once had a couple of O2 sensor wires get too close to the header and melt together and the car was doing all kinds of crazy things once the car warmed up and went into closed loop. We like to never found it .

Good luck. These things can be very frustrating.

Injuneer

Probably doesn't matter. He signed off a few minutes after his original post, 10 days ago and hasn't signed back in. Guess it wasn't very important.

David94TA

Well, maybe he will sign back on sometime. Or, maybe this will help someone else. I'm always a little hesitant to answer new posts right away since there are a lot more experienced people on here.

Injuneer

From the instructions, sounded like a code lights were all pointing to the cam position signals from the Opti.

camZ2894

Hi guys, sorry for the late reply. Bob got back to me and I ended up sending the box back to him. There was water and corrosion in the box. He said the orings were missing on the screws and the cover gasket was cracked probably from being over tightened. The mechanic that has it now said there was an oring around the whole box which was cracked but none on the screws. Checking up to see if this is plausible. I can't remember if orings came with it or not. I ordered it from Lingenfelter - which btw has horrible customer service. Do not buy the LTCC from them - buy it directly from Bob. Bob cleaned it up and tested it - said its working now with no issues. Hopefully this solves the problem...

David94TA

Very good. Let us know if that solved the problem.

camZ2894

The boxes have a silicone gasket that is attached to the lid. It is molded on when the boxes are made apparently. It can crack if the cover is over tightened. The box company has a replacement gasket that can be installed on the box if the molded on gasket gets damaged.

Injuneer

Thanks for the update.

camZ2894

Update: box is back in and good - still coming up with a code 3 which now we have come to the conclusion that the Opti is bad - the one that the incompetent mechanic supposedly replaced. Not too happy right now given that I already paid for this kind of labor and the part. The mechanic that is working on the car now said he would just go with a no name Opti bc the AC Delcos are expensive just for the remanufactured ones. To me I'd rather spend the money and not have another problem. Anyone use a no name brand opti with the conversion? Wondering if the no names work just as good given that I have the conversion that redirects the high voltage anyways. Thanks.

Injuneer

The "no names" are mostly Chinese ripoffs. The auto parts store and other alleged ignition specialist parts are crap shoots. Pretty much comes down to the lower the price, the higher the chance of rapid failure. Not all of them fail, its a gamble. You might get lucky. Even the AC Delco or Delphi can have problems. And the MSD will have as many or more failures than the AC Delco.

How much does he want to charge you for the AC Delco?

Have you scanned the PCM for codes - there are two for the Opti cam position sensor, and the critical one, DTC 16 doesn't turn on the SES light. There is a how to for checking the Opti signals on Shoebox's site:

4th Gen LT1 F-body Tech Articles

David94TA

I think that the general consensus here is to stick to the AC Delco opti.

You have a '94 which uses the "non-vented" version. If I were going to all the trouble to change it out, I would convert it to the '95 vented opti. I have a list of everything needed for the conversion somewhere that I will be glad to find if you want it.

The last time I looked, I think that the vented opti is actually less expensive than the non-vented ones. Someone correct me if I'm wrong.

Additionally, if you do get a new opti, have your mechanic take it apart and replace the plastic rivets holding the metal bar to the rotor with metal rivets. Make sure the rotor will still turn and that the new rivets don't rub. Also, put locktite on the screws holding the rotor on. These are known to back out.

Injuneer

That swap is a pretty substantial undertaking - wiring harness, vacuum harness, timing cover, timing set, new cam. Cheaper to buy an unvented AC Delco, then get an MSD cap and rotor, which is vented for both 93/94 and 95-97.

Shoebox has it covered:

http://shbox.com/1/4th_gen_tech2.htm...p_requirements


AC Delco has also complicated the issue of replacing the rivets, loc-titing the screw by sealing the case and voiding the warranty if the seal is broken.

camZ2894

He said I was looking at about 900 dollars for an OEM Ac Delco which are all remanufactured because they don't make new ones anymore. I found one from summit racing for $380 AcDelco


Thanks a lot for the article. I sent it to the mechanic. He said he did see a code 16.

camZ2894

That's good to know about the MSD cap and rotor - Ill look into doing that. Just speaking with people/mechanics, I've come across people that say the LTCC isn't worth it because it still uses the opti spark low voltage. The reason why I did it was because I read that since the high voltage is redirected through coils, the opti has less of a chance of getting overheated and lasts longer.