I just bought a 2006 tahoe which was a bank repo and we have no history. It appears stock but has a CIA and some sort of aftermarket muffler. Truck runs great but pings terribly under WOT after engine hits about 4k. Sounds like bb's being poured down intake. There are no codes, but Im thinking either it has a botch tune/programmer or Knock sensors are not working ot both? Anyone ever had this problem? I wouldn't think stock tune cld ping this bad even with no sensors?

 

I did a log and absolutely zero KR while it's pinging it's head off. It even pings at the hit of the throttle. Timing during WOT goes to about 30* @ .56 g/cyl and 4400 RPM but timing in high oct timing table is 24* at that value. Something somewhere is adding 6* of timing.. Appears that the IAT sensor is working, and coolant temp sensor is working Narrow band is 830 mV @WOT.

 

How many miles are on this thing? I've seen them before with excessive carbon buildup in the head. For what the Narrow bands are worth, it looks like it could use more fuel. You know how to tune so you know the obvious stuff. Look at the tune. Post up the tune.

A tune commanding 30deg at WO doesn't sound stock.

 

Sound like you guys are on to something. Carbon and go back with stock programming.

 

Thanks guys. I think the programming is stock is the prob. It's commanding 24deg but seeing 30. Something is going on but even at 30 it should not ping this bad id think. Tahoe has 120k miles on it. Yea prob have to buy a lic and tune it a little. Sucks that I can't ream it and clean it out, just pinging so bad it would end up blown up. Might just end up throwig a lq4 in the damn thing lol

 

What software do you tune with? 30 deg is a lot for a stock motor on 87.

On that note, I've seen a couple motors not show KR and ping. They would show KR and then zero out before they would ping.

Run some top end cleaner through it. A stock tune should not command that much timing at WO even with 6 deg being added.

 

A stock program will not command 30 degrees of timing, anywhere.

I just checked a stock tune on HPT and the High Octane table commands at most 24-25 degrees @ .56g/cyl. The Low Octane table commands 20 degrees.

Sounds like a crappy tune to me.

 

if u dont wana pay the 2 credits, maybe you could have the pcm reflashed to stock

 

Look at the fuel spark correction table. It adds timing when the commanded AFR changes. That is where your most likely adding timing on top of the High octane table

 

Cats going bad? To much back pressure? ( I'm thinking out of the box )