Need help tuning. Breaking up at WOT. PL file attached


Active Member
Aug 10, 2009
Went to the track yesterday and I've got issues, so I am looking for ideas on how to approach this. Attached is a PL file of the run. Here are the issues. The engine is breaking up at WOT in each gear and also backfired. There is Kr at each shift. My alky is on and set at 6 on the dial. Fuel seems to increase as does boost. It has new spark plugs (autolite 23s set at .028) and wires. The heads, intake and SD2 chip are all new. Thoughts?


  • WOT pass with breakup.dat
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what springs are on the heads? How much preload on the valvetrain?

I looked at your log and it was not doing what mine did with bad valve springs , you probably have ignition problems somewhere other than plugs . Do you have a tester for the module and coil ? Caspers sells one and worth every penny .
Back in May at the Gbody Nationals at Richard's I thought I had this diagnosed as a bad coil pack. Using Richard's tester we determined the old coil had a skip and you could see my volts were dropping off during WOT in my logs, so I picked up a HD coil pack and it seemed to fix the problem. With this HD coil pack I don't see any voltage drop at WOT in my logs, but I have the breakup problem. I do have another coil pack I could try... I was wondering if I'm getting too much Alky spray causing it to breakup and backfire? Anyone ever experience that?
my alky is set on 6 just as Razor says and mine works perfect, if you think its alky try turning it off and lower the boost and see what happens .
if its rich misfiring, the wideband could be reading artificially lean.

try turning the alky down a little, and set your target afr's to 10.8

doublecheck the coilpack towers for rusty+crappy deposits, and inspect the plug wires for worn/burnt spots.

how old are the plugs?

Update. I decided to turn my alky down to 3.5 and set my target AFR to 10.5 and I made a pass yesterday. The PL file is attached but basically the breaking up went away. The SD2 chip was adding up to 18% fuel, so I think I need to up parameter 8 to get it close and then work the VE tables.


  • steve wot alky on 3.dat
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I was chasing some issues with my car last year that sound similar to what you got going on. I changed plugs/wires/module/coil/battery/alt/and battery and alt cables, triple checked all grounds. My car felt like it would stop reving at about 4800 and hesitated shifting (sort of just layed down).I was in the process of tuning for the achly and slowly turning up the boost. Didn't start doing it until I got over 20#. Backed it down to 18# no issue. I was looking at the trans or valve springs next, it ended up being too much alchy. Mine was set at 6 dropped it to 5 and the car didn't do it as bad. Backed it down to almost 4 and it totally cleared it up. I have a wide band and was logging while trouble shooting but it was not showing an exceptionally rich condition as this was happening. At wide open I was seeing 10.2- 10.4, I know that's rich but I was surprised how the car acted from a little too much achly.