So i recently put headers on and made my own y pipe into 3 then over the axle. I can either run stock, dynomax, flowmaster or just a muffler delete all changeable in about 10 minutes. I removed the air pump but left the egr on because i don't have the computer tuned. The oxygen sensors are in almost same spot as factory. After i got it all done it felt rough at idle brought it up and put on the sun beam found high firing kv on #2 and low firing kv on #6 looked and the number 2 wire was off??? no worries.... But it still feels like a slight miss could the low kv on #6 possibly be caused by maybe a plug wire arcing out or maybe a small gap on the plug which is causing a slight misfire. Also hooked up to the tech 2 the last day of class and looked at my data stream. At idle it had anywhere between 22-28* of advance and at 3,000rpm 34-37* advance and at 3,000 rpm it hit 42*advance i talked to an engine builder at my store today about it and even with the stock 10.5:1 ratio he said it shouldn't go past about 36 37* at wot. He said it may be running lean but i highly doubt it cause when i added a shot of propane during the emissions test the hc barely went up. I'm thinking i may have to get a tuning program so i can back the timing off

BY the way did an emissions test on her too
state of mn i believe is 200-400 on hc at idle mine ran 2100 hc at 3000+ had 3100-3500

co was at 8.9 i believe
and o2 was 3.9???? i think its been about 7 days

 

back to the top
cmon someone has got to have a little insight

 

Might want to add basic info about the car - year, model, engine, tranny and any major mods. Is the tuning stock, or customn?

A "Signature" is a good idea.

 

oooootay sig is up

 

Since it appears you have stock tuning (and timing tables), you should try and figure out what the problems are before you start playing with the timing tables with tuning software. The stock LT1 tables provide 33-35* of advance at 90/100kPA MAP (WOT), with another 3* that gets added outside the tables. The numbers you posted are confusing (you indicate 34-37* at 3,000rpm, then say 42* at 3000rpm???) but may not be out of line. At less than WOT you will see advance well up into mid-40's at cruise conditions. If no one has changed the timing tables, you are getting the exact same advance that every other stock LT1 gets, and they run fine with those levels of advance.

What is the idle speed? That's where your numbers look a bit high? 19-22* is more normal with the correct idle speed.

In any case, too much timing would simply put the engine on the edge of knock (detonation), with the knock sensor/PCM pulling out timing to eliminate any knock. That will results in a power reduction when knock retard is encountered, but it doesn't account for the misfire you seem to be encountering.

The HC numbers would appear to indicate its running rich, at least if the cat is working. Do you still have the cat? Leaks in the exhaust before the O2 sensors, or misfires due to burned plug wires will cause it to run rich, and the burned or arcing wires would account for the misfire.