Silver02Z28

iTrader: (2)

This seems a bit off. I noticed the car losing power and ran some tests.
At WOT the LTFTs are 4.7 and 3.9. STFTs are 0. IAT is 63 and coolant temp is normal. The 02s were around 890mv.

I keep throwing p0420 and p0430. The rear 02 signals do not look like the front 02s. They don't seem to switch up and down in a nice pattern, but switch randomly and go flat for a while. They do jump to 800mv+ at WOT.

I'll confirm this, but when the engine is cold the timing is around 25 at WOT and seems to run very strong. When the temp is up to normal operating the timing slips to 13.5.

I have replaced the MAF with a stock screened unit. My other MAF died and I was in SD for a while. I have had the intake manifold off recently to fix some leaks in the knock sensor o-rings. Maybe I need to torque it down again. I've also checked for vacuum leaks with starter fluid but could not find any.

My mods are in my sig. (No ported MAF or descreened MAF)

sleeperstyle

iTrader: (4)

try re-setting the pcm. sounds like it could be on the low-octane timing table (limp mode).

unless, of course, the timing is getting pulled out because of kr.

oh- 800mv is lean, you want to be at least 860mv at wot. granted all cars are different but i know 800mv is lean, i will see alot of kr at 800mv during wot.

horist

Those PO codes are for catalyst inneficiency, they're being set because the rear O2s aren't reporting what they should... indicating failing cats

13.5* of timing means you're in the low octane tables... are those the only P0 codes you're getting?

Reset the PCM as suggested , if it continues to use the low octane tables make sure you're not getting alot of Knock Retard... Scan the car and see what your KR is

Silver02Z28

iTrader: (2)

Those are the only codes. I'll take your suggestions on the reset and check out the KR.

*edit*
My MAF died and threw a P0102 and the performance went south. I replaced it and pulled the fuses PCM BAT and PCM IGN. It seems to run the same as it did with the bad MAF but the P0102 went away. I'll pull the fuses again and let it sit a while.

Silver02Z28

iTrader: (2)

I reset the PCM again, correctly this time. I drove around and got it up to temperature. I did several WOT runs and found the timing advance to be in the mid to low 20s and the LTFTs where 1.6.

No doubt all the power is back. What a difference!
Thank you guys for the help!