Just thinking out loud, but do you really think the injectors would fail when hot, if they perform fine all the other time? Im by far not an engine expert, but I would think your injectors are fine. I know you re-did your plenum.... is there a chance it went again for some odd reason? If you just said above that you get no ping with the 87 tune, but your prb still running high octane, .... plenum?

 

Not plenum,

Verified visually by myself, with a vacuum gauge (21 inches at idle, 21-25 driving), and visually and with a machine by the Tech.

I don't know enough about injectors to know what happens when they get hot, but your right and that doesn't seem to make much sense.

 

I have 2 bottles of octane booster, but i don't want to add them as I believe that will "fix it" without actually fixing it.

Perhaps I do have a jam up in the cooling system somewhere and a machine flush might help. Probably due for it anyhow.

 

if you've removed the msd, switch the plug gap back to ~.035. I initially thought your problem was cold start related... with your update and what you've done. do the .035 gap & let us know.

 

Run that tank of gas out and go some where else to fill it up and put a couple bottles of Techron Plus in and some MMO.

 

Well zman,

The tech seems to agree with you. Got it pinging today and took the tech out and he said, "step on it until it pings, then give it just a little more and see if it gets worse." It did. then he said "now do it again and then really get on it", I did and it fought through the ping and cleared up. He swears he thinks its just too low octane gas and told me to throw 2 bottles of octane booster in there and run it as dry as I can before refilling.

Not sure why the pinging reduced when I changed the plug gaps if this is truly the case.

I did have a REALLY bad ping a week and a half ago, I could barely touch the throttle and it would ping. After refilling at a Chevron station with 93 octane and 2 bottles of Techron concentrate plus (the biggie sized 20oz bottles) it has gone down. So now the tank has 2 bottles of Techron concentrate plus and 2 bottles of octane booster. I should be able to drive it to the moon now, or melt my injectors.

The tech thought that with a 35 gallon tank even on "E" there's still about 8 gallons in the tank and if it the gas was a lower octane, then 8 gallons would still be enough to dilute the other 27 gallons. It's possible that one of the stations I've stopped at accidentally dumped the wrong octane gas in a holding tank, or maybe I pushed a wrong button at the pump. I'm pretty wary of that as I know I need the good stuff, and I'm the only one that gasses the truck up. Wife won't drive "that damn loud thing". Anyway, I only ever use Chevron or Quiktrip as they're both top tier and turn over they're gas pretty quickly. And I absolutely never, ever fill up when the tanker truck's dumping a load into the tanks.

 

UPDATE 11/16/08,

Still pinging. Ran a tank full of Chevron Techron Concentrate Plus (2 20oz bottles in 35 gallons of gas) down to 4 gallons left and refueled with premium from a Chevron station and 2 bottles of Mopar Fuel Injector Cleaner. At a half tank of gas, I'm still pinging, and I ran 2 cans of MCCC prior to starting this gas treatment procedure. Pretty sure Carbon buildup isn't the culprit, matter of fact, carbon might have been filling the cracks between the valves and I've just removed it all.

Here's what's gone on so far:

1. Fixed Freeze plug leaking coolant. UPDATE: found another coolant leak yesterday at loose lower radiator tubing. Hopefully this issue is done. I will verify today and pull the radiator cap and check for bubbling after warm up to see if there is a cylinder head gasket leak somewhere. I do get white smoke on start up, but I don't recall seeing any idling at a light. This could just be condensation from the cold mornings. Looking in the rad should help verify.

2. There is no plenum leak. Checked visually and with a vac gauge.

3. FULL tune up done, ALL ignition components checked. Plugs looked good, no oil or other visible signs of problems.

4. Truck will not ping with stock program on 93 oct, it will with the SCT tune. It did not ping with the SCT a month ago, now it does.

5. Oil consumption is not an issue. There was no milky/chalky oil just last week when I changed it.

6. No CEL's. No engine misfire codes, random misfire codes, NADA.

I think I'm down to cracked heads, but I'm not 100% sure. Anything else I could try? I HATE GREMLINS!

 

when you did the sct tune, did you reset the pcm at all?
edit: forgot to mention that it could be in the adaptation stage when it did not ping.

couple of things to mention...

fuel pressure, you could be at the bottom end of the spec and may be running slightly lean for the tune.

o2 sensors, clean or swap both (for 2000 & up) your front o2's they may be slow to respond and will not throw a code.

fuel cooler... remember this fixed my pinging problem with an agressive tune on the bmw 325... (this would include wrapping the fuel rails.

 

i'm just guessing and throwing out ideas.
assuming that pinging is caused by lean or hot conditions, or timing being off...
is your timing sprocket set at stock, or 4* adv/ret ?
could a crank pos sensor or cam pos sensor be bad, and throwing off the pcm ?
how would a cracked head cause ping ?
could one or two or all injectors be starving/malfunctioning. how to know ?
edit - good point above steve, does it ping immediately after pcm reset or later, after its thought about things for a while. also, could the o2 sensor be taking it too lean in an effort to reduce emissions. false reading maybe.

 

you have a good point there, the crank sensor could have enough error in it to contribute to the problem, however he mentioned that it was fine a month ago.

Squirrel, did you look at ALL 4 corners of the plenum? could be that you have a leak starting that is contributing to the problem along with the advanced timing of the SCT...