Well, I have an odd one.

I'm getting random pinging issues. There are times when I start up my truck and I swear it's knocking on turnover, I barely tap the gas and it'll ping louder than all get out. But if I shut it off and restart it, it will sometimes go away.

The plenum gasket is not blown. I'm pulling 21" of vacuum at idle and it stays there or above while driving.

I've tried colder plugs, 180* t-stat, and even asked Hemifever to pull timing out of a couple of SCT tunes to fix it, but nothing's worked.

I fear I might have a cracked head, what would be the best test? Compression or Leakdown?

 

Mise well do both tests to make sure. I got both done on my old mustang for $20 but... doubt you'll run across that. Try an autozone to rent the tools and have at it (if you have an autozone around u), but your on the right track in my opinion. You have more knowledge than me, so I can't help you out too much. Wish ya luck!

 

does the pinging go away if you use 93 octane gasoline?

 

Does it depend on the temp outside? Does the truck run hot? How many miles? When was the last time you replaced the plugs and wires?

 

Dude, pull the sct program out. Let me know what happens.

 

maybe you need a new timing chain setup. could be stretched out.(just a guess)

 

+1 I had to pull my SCT program out because of pinging which is either related to my 10 deg. of timing retard from a bad timing chain or dirty injectors that can't keep up with the fuel demand.

 

HankL,

It's currently running on 93 octane. I pulled the SCT tuning off of the truck and at stock tuning, it would not ping with 93 octane. I tried everything that made it ping with the SCT tune and nothing.

I tried an old 93 octane file that Hemifever gave me and it pings as well.

Talon6 and xskylinedx,

Timing Chain was replaced 8K ago at 77,000 miles. I don't believe that to be an issue because I would expect complete failure if I were to have a timing issue and not simple stretch in 8,000 miles.

Aubrey,

Cap, plugs, and rotor are all relatively new and in good order. Plugs were pulled just last weekend to check on them and they're good. They have a uniform red clay/rust type coloring. It doesn't ping near as much when the engine is cold, which is another reason I'm thinking cracked head as I'll bet the crack opens up when the head heats up.

I'm leary of blaming carbon deposits too as I ran 2 cans (back to back) of MCCC just last month.

It could be dirty injectors or an ailing fuel pump (still original) that can't supply a solid 49psi. I'm running the 20gal chevron techron plus on 10 gallons of gas right now. I'll stop by the dealership for some injector cleaner as well. A fuel pressure gauge might be able to tell me something as well.

This all happened fairly suddenly, and what felt like in the "middle" of a tank of gas, so I can't even rule bad gas in or out. I've heard stories of tanker trucks dumping 87 into the 93 tank and vice versa, and I typically fill up at half tank to full tank so maybe this last half is a lower octane, though I would think it should disperse

I will also say that I haven't received 1 CEL or thrown a single code, and some of the pinging had been so severe I was concerned about punching a hole in the piston crown. I thought for sure I would get a cylinder or random misfire code.

NEW DEVELOPMENT:

I got out to just to visually inspect the engine and I found a coolant leak in 2 places: right down the center of the dust plate covering the Tranny, and on the driver's side right in front of the starter.

There's no leaking from the front of the engine, around the timing cover or the freeze plugs. So what could that be? I cannot see the point where the leak is occurring and I was wondering if there's a crack in the cooling jacket causing overheating of a certain cylinder or neighboring cylinder. The motor oil is not milky, gray, or chalky at all.

 

Your coolant issue sounds more like the heater core or a hose to it that is leaking. Unless you are getting really really hot, I doubt that is your pinging problem.
The fuel pressure would be a good check I think.

 

heater core's on the other side of the truck from the first leak but I'll take a peek at it. Fuel Pressure tester is on the list for this weekend.

Damn, and I had to fill up tonight too.