Here's the situation. The shop has a '97 Caprice w/ LT1. They had to replace the tranny in the car. While they were at it, they replaced the plugs/wires (routine maintence; nothing wrong) Since putting the tranny back in, it misses on 2,4,6,8 cylinders, sets a misfire code (0300) and dumps black smoke out the back of the car. When its first cranked, it seems to idle ok, but as it gets warm, it gets worse. I thought it might be an 02 issue, but they've been checked. They hooked a scanner up to it and it showed the timing being anywhere from -17 to -28! Anyone have any ideas on what to look for??!!??

Thanks for any help!

 

Most likely, the scanner you are using is showing "advance" as a negative (before TDC) event. The scanner shows you what the PCM is calculating for timing, using the spark tables, less any knock retard. If you were looking at the spark timing at idle, those numbers are normal... 17-22 deg advance, and if you rev'd it a little, you might see 28deg advance.

Now, if you were looking at the "knock retard" field, you have a problem.

 

The timing you see is normal. What you are seeing is advance (BTDC). Some scanners read it out with a "-" and others don't. Nothing to be concerned about, there.

I would be looking more into what wiring they might have damaged during the tranny work.

[edit] too slow...again...:blah:

 

Thanks for the info guys! Now it even has another problem. The gauge is reading that the battery is low, however, the alternator was checked and is fine and the battery is new. I'm starting to lean towards a bad PCM. Any thoughts on this along with the other issues?

Thanks again!