kcorus

Hello, I just recently picked up my 1st Corvette, an '87. My mechanic checked it out before I bought it and discovered it may need a, intake manifold gasket. The seller (car place across the street, we have a small town) agreed to repair it as part of the sale so I went with it.
Turns out it was a crack in the MAF housing.
Tooke the car home all fixed up and on came the service light a few days later. I pulled the code and it was a 13, O2 sensor circuit. Before bringing it back to my mechanic, I went and replaced the O2 sensor and all plugs. Ran awesome and still is, but after 15 minutes or so, the light pops back on. It will clear when the car is turned off and restarted but will come back on after about 5 minutes. Same code.


Where can I look next?? I believe the O2 signal could be symptom not the trouble but not sure. Dirty connector? MAF still no good?
Any ideas, please help.

John A. Marker

I had something similar happen on my 85. Just could not figure it out. Had my tuner (who is also an electrical engineer) trying to figure it out also. Replaced the O2 and it would throw the code in 5-10 minutes of driving. The O2 sensor is a single wire and one would assume that the ground is the exhaust pipe itself. Turns out there is a wire from the computer (mine was orange) that was the ground for the O2. It came from the computer and was grounded to the engine. I know doesn't make sense! We ended up testing it by running a temporary wire spliced into the old wire to a ground on the top of the block. Problem solved. We then installed the new wire permanently.

You might just check that out. You will have to do a search and find a drawing of the two plugs that go to your computer that lists what each wire is for. My drawing is for the 870 computer and yours should be different.

kcorus

Thanks !!! I will try that solution ASAP and let you know the results. Finger's crossed

kcorus

BTW, where did you make the splice? At the unit itself or up in the engine compartment? Did a quick search for the type of ECM I have, nothing so far. The quest is on.

John A. Marker

If you can find the wire (assuming there is one for the 87) then just run a temporary ground and see what happens. We fastened mine to the bolt on the water neck on the thermostat.

Found it....just took a little searching.....

http://home.earthlink.net/~cliff_har...s/pinouts.html

Pin D6 TAN WIRE.

http://tpiparts.net/1227165_pinout_diagram

70ZZ3 96LT4

Do not know how your 1987 is configured. My 1985 was giving me a intermittent Code 13 that I fixed. Replaced a temp sensor that screwed into the top of the EGR valve. This was many years ago, still no Code 13's.

John A. Marker

Once we identified that the new ground worked, we just cut the original wire about 4 inches from the plug and soldered it to the new ground and covered the splice with heat shrink tube.