Sorry for posting this in here, but I'm not getting any response in the other sections so here goes:

My O2 sensor wire (purple) before the connector got too close to the exhaust manifold and it melted/burned the plastic conduit to it and fried about 2 inches of insulation off as well. However, the bare wire section did not ground to any metal or to the coolant gauge sender wire (green one). Knowing that my car has never run quite right once it warms up (rough idle, power loss), my questions are:

1.) Could this damage cause flaky O2 readings in closed-loop and possibly my driveability problems? Interestingly, after I installed Accel #23 injectors with about 43psi of fuel pressure, the car never leaned the mixture in closed-loop. No trouble codes.

2.) Can I fix it by simply splicing in another piece of 18 gauge wire using gold plated connectors and insulating it with thermo shield?

Thanks guys, I'm no electrician .

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1990 IROC 350
Mods: Too busy trying to make it run right to mod it.
Airfoil, Dynomax cat-back, MSD coil, 180 t-stat, Bald Eagle tires,
Hypertech fan switch, Accel 23# injectors, Holley AFPR, ported plenum,
Ported Daytona Yellow stock base, Moroso valve covers, other stuff,
Ruger P95DC, hot wife, new oil filter, thick rubber floormats, no cats.
18.0 @ 85MPH since I'm one big-a$$ MF
"It's better to have and not need than to need and not have."

 

Jethro,

The EOS is a very sensitive circuit. The signal levels are very small and a very small difference in voltage output can make a significany difference in mixture control. Simply exposing the wire to heated air may have changed the wire's resistance slightly, but not enough to alter the signal back to the ECM enough to make any difference. If the electrical connector at the end of the wire was damaged, however, your signal may have been degraded enough to alter the mixture.

Understanding that, it is extremely important to have very clean and solid electrical connections to the sensor. If the wire is still intact, I would advise reinsulating the existing wire with a self vulcanizing coating or wrap. Obviously, rerouting the wire and/or heat shielding would be a good idea.

If the wire is damaged (not the insulation, the copper wire itself) you'll need to replace it with the most secure wire connectors you can find. The heat developed by the exhaust system precludes the use of common solder alloys to make good connections, so plated compression connectors are a good idea.

As for the 23# injectors, they are fairly close to the OEM injector flows and the pressure you indicated isn't significantly higher than stock. It is possible that the system was satisfied with "nominal" injector pulse rates with the new injectors and pressure setting. Given the fact that you are probably flowing air a little better than stock, the extra fuel would be just about right to maintain the correct mixture.

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Later,
Vader
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"Let the bodies hit the floor!"
Adobe Acrobat Reader

 

Vader, thanks a bunch man. This has been eating at me for some time, since I decided to tear the top end out of the engine and go over it thoroughly, along with the the wire harnesses. I don't think the wire is damaged, but it does look tarnished and could be nicked in some areas over the uninsulated length. The strands are also separated rather than twisted together like a rope. Does this have any effect? Maybe I should try wrapping it like you said, and if I don't feel good about it try splicing in a new piece later. Thanks for the help.

 

I don't know about the splicing trick. You may be better off just getting a new sensor.

On my stock O2 sensor that I just replaced, the wire is, uh, well, I don't know what exactly it was. I do not believe that it was copper though. I'd guess steel. It was very tough to cut (as compared to copper wire), and soldering it would be like trying to weld with a propane torch. The connector wasn't even soldered to this wire, it was just crimped. Steel wire would make sense due to the high heat that this sensor encounters, although I don't know what aftermarket sensors use.

The insulation on this wire was probably TeflonŽ (I think). Certainly not your common rubber or PVC insulated wire. If I was going to splice into it, I'd have had to use my mini ocy-acetylene torch and weld or braze or silver solder another wire to it. Since I don't have any insulated steel wire, I'd have had to use copper .