I posted this in tech with a typo in header that I couldn't seem to correct so I decided to repost here, since I wasn't getting feedback, sorry for the dupe. I couldn't delete it there either.

How I missed the fact that the ALCL plug was cut out when I bought the car, I'll never figure out. I guess there were so many other problems that I overlooked it while dreaming about what a little TLC could do. So I have no codes to look at.

This is a Connecticut sniffer test. Passed NOx with 455 out of possible 614. Failed HC with 129 out of 88 and CO with 1.20 out of .28

She was running so sweet I thought I stood a chance. Came home after the test and put my little home CO meter on there and sure enough see about 1.5 out of drivers side, but passengers side looks to be .5 maybe even within spec. Checked it 3 times and every time the meter would decrease when I moved it to the passenger side exhaust.

As I said there is no ALCL plug, so can't check for codes! Previous short term owner claims he replaced injectors because it wouldn't run, also replaced cap and plugs and wires (before he did injectors).

I went to check the air cleaner - and there was none installed! I'm guessing that a good air cleaner will make little or no difference unless it's screwing up the computer, I think I'll go yank the one out of the 85' to test that.

Anyway, anything obvious to try with one side rich and one side lean or at least close to right?

 

Does it have true duals or stock style exhaust.

With stock style there is no reason for one side to differ as exhaust comes from the main cat and branches with the rear Y-pipe to each muffler.

You really need to get an ALDL connector and wire it back into your car. That is the link into the computer to get trouble codes and to access some self testing features available. Contact Contemporary Corvette (link on my site) to see if they have a used unit.

 

Duhhhh, I should have realized there was just a Y pipe there - maybe I should just poke as many holes on the other side.....

Putting air filter in didn't make any difference as I suspected.

Is the ALDL on the 88 the same as the ALCL on my 85'? If I could prevail on you again for the wiring on the ALDL, and they function the same, then only 3 wires carry the code signals?

 

Just because it splits doesn't mean it'll flow equally You could use a little fan flow probe to check flow rates out of the pipes to call them equal.

 

Though the flows may not be equal from each side my point was that, since each side's gasses come from the common pipe, the composition of gasses in either tail pipe should be the same.

 

Yes, clearly the difference in CO from side to side is due to some pinholes in the tailpipe on the passenger side that I hadn't noticed. They are probably causing a combination of leaking CO and maybe "sucking" in some regular air. Although now that I think of it regular air registers higher on the CO meter - maybe my problem is too many pinholes that I can't see on the drivers side!

 

P.S. thanks again 65Z01 for sending the diagram. I'm going to do a little studying during coffee this morning and see if I can't get a connector this afternoon to splice back in. Appreciate all your help.

 

Where in CT are you located?