After my 87 GX failled badly, even with some extra GL antifreeze in the tank, kinda figured the CAT was finished. Spark plugs looked OK, and the air pump appeared to be working, so decided to just change the CAT and see what happens.

LIMIT INITIAL TEST RETEST

HC 105 278 14
CO 0.58 1.19 0.02
NO 1179 515 55

IDLE

HC 300 398 7
CO 1.50 0.05 0.00

Turns out the old CAT was partially melted inside, and had been on the car many years anyway. The replacement CAT was just a generic inexpensive replacement (about $100.00). Final etest for my 87!!!

 

So you didnt need to convert it to a 5.0L V8 to pass??

 

booo. V8 wannabe poser!

Anyhow why don't you try methanol mixed in with 94 octane

I know I will have fun trying to pass emissions.

Gonna try 4"cat and airpump rigged.

Also play with timing

 

I guessed Right!(yippy!)..Said the Cat was Most likely Toasted...ok..so that's one Good guess and 4,999 well you were Close but,No's!

 

Ian - I had 1 1/2 L of gas line antifreeze added to less than 1/4 tank of gas, and I stlil had HC's of 278. Replacing the cat brought it to 14. The chart is not quite clear as it didn't come out with the spacing included. Let se if this is better.

/ /LIMIT / INITIAL TEST / RETEST

HC / 105 / 278 / 14
CO / 0.58 / 1.19 / 0.02
NO / 1179 / 515 / 55

IDLE

HC / 300 / 398 / 7
CO / 1.50 / 0.05 / 0.00