Have a 87 IROC that was an electrical Nightmare until recently. A remote start and alarm was installed when all the problems started. Had a meltdown on the MAF, TPS, Pickup Coil, and a few sensors to boot. When the car was returned after repairs, it kept spitting out a tps high, tps low. I changed the tps and it ran 90% again. But, the car takes an extra long time to go into closed loop. Is it possible that you can have interference from a 6 gage wire that was too close to the distrib or ESS or other component on the firewall that would prevent from going into closed loop.
Now after the my new mod engine was installed it gave me time to check all the wiring to find that the idiot that installed the remote start, pig-tail spliced all the wiring and covered with electrical tape. He did a real bang up on them. They have been all fixed and soldered and heat shrinked now. Still have the closed loop issue though

 

That's very typical of most of the "professional" alarm, remote start/lock, and audio installations I have seen and repaired. Installations with twisted and taped wires, Sta-Kons, Scotch-Locs, wire nuts, and other purely mechanical means without adequate sealing or anit-oxidation compounds are basically timers that "go off" in 2-3 years. You take it back after the warranty expires, the "professionals" that installed them cannot troubleshoot them, so they sell you a new one, and hack the wiring together again. Since the Beavis & Butthead connections are new, they work, and the seller surmises that the old hardware must have been bad. 2-3 more years, and you're right back there looking for answers. It's a lot like Honda wiring. It's as if they are allergic to solder, WeatherPack connectors, or antioxidation paste.

As for the potential interference, unless there is some fairly high current running through that AWG6 wire, there should be nothing induced into the HEI or EST wiring. If you suspect a problem, reroute the wires so they cross instead of following parallel paths to minimize inductance.

How long to achieve closed loop? There are both cold and hot start timers programmed in the ECM for closed loop. The oxygen sensor also must be producing crosscounts, and there are some CTS parameters involved.

 

Closed loop usually takes place now within 4 to 6 minutes sometimes. I know I can change and probably will change to a heated O2 sensor because of the Jet coated Headers. But, this problem took place long before the Mod engine. I will re-route that wire in question by drilling the fire-wall and grommeting the hole. You really shedded some light on these 2nd hand installers though. It was exactly like you said. After 2 years it just stopped working.. Then 5 months to figure the problem out just to get it running only to have a major electrical meltdown. The 1st thing I did do was to pull out any thing that was not standard for the car, minus the stereo and Amplifiers. Thanks for the help, It is much appreciated.

 

I don't understand the mindset of performing a bad job...ugh. I hate to say it (as I'm not certified in ANYTHING), but there really should be a concise certification required before anyone can install aftermarket accessories for profit. The only problem I had in doing my alarm was my 100W soldering gun wasn't hot enough for the ignition wiring. I had to carefully use a propane torch.

 

So true. Every once in a while you find someone that has a clue but about 99% of the time thats not the case. A friend of mine had a stero installed and all of a sudden his speedo needle started bouncing with the radio. Of course the place said they didnt touch the instrument cluster so its not their problem. Luckly for them my friend now seems to think its cool so he doesnt care.