Changed to larger headers last week and my tuning has been effected a lot. Motor pops and sputters at low RPM's(1200-2800) between 1/4 and 1/2 throttle when it seems that my throttle input is not enough to downgear. Once I allow it to go to a lower gear it clears up. Seems to break up a bit in high RPM range at WOT. Couldn't get an appt. with my tuner until next week but, would like to have an idea of whats going on in case I shouldn't be driving it. I'm not sure where to start (AFR, tranny settings, etc). Anyone have experience on whats going on and what changes to make with HP Tuners?

 

There must be a leak, increasing the diameter of your primary tubes should not change much unless you were on the verge of being lean before the upgrade. Post a scan log.

 

Check your plugs, and wires. Mine acted similar when my lt burnt a plug wire.

 

Check for a a cracked spark plug or a wire not pushed on all the way.

Or use HP Tuners and check for misfires on each cylinder individually. Makes it really easy to narrow down.

 

like people said above, its very easy to crack a spark plug while doing a header swap and never notice it. That would be what I would check first

 

Sounds like an ignition type miss. Like stated above it isn't hard at all to bump a plug and crack the porcelain on a spark plug you may not even be able to tell just by physically looking at the plug either. But you'll sure know it by the way it runs!

Had a big I told you so moment with a buddy of mine back in the day. I was over at his house when he was changing plugs in his car and one of the new plugs rolled off the battery where he had them setting on and it landed on the cement and I told him I wouldn't use that plug it could have cracked the porcelain when it fell. He says well it looks fine to me. Well he didn't listen to me he called me up later that evening and said man my car is missing pretty bad now, guess what it was.

 

Thanks for the tips, I'll try to change the plugs tomorrow. I thinking was because the exhaust is freed up so much more now that the AFR is too lean.?. But, my lack of knowledge is why I have to pay people to tune it for me. Anymore input is appreciated.

 

Yeah, that's what I meant when I said "leak".

 

I changed the plugs AND had my tuner look at it with HPTuners. New plugs did not help at all and my tuner could only see that the O2's were a little erratic at part throttle...which is when it pops and sputters. No answers yet. Check engine light has not come on. Any answers are appreciated before I go drive it off a cliff.

 

Popping and sputtering MIGHT be idle air flow...I upped mine a tad just today and started noticing a little bit of popping/backfire on gear shifts. I would definitely suggest taking a look at your VE Table...never hurts.