Not sure how best to proceed, sounds like detonation and then smoke

[Kumba]

So this issue has started to get worse lately. Apparently it's bad enough now that I can get smoke puffing out the exhaust. Robot let me know about it a few weeks ago. I always figured it was a sticky injector but never had much in the way of smoke before.

Here's the symptoms:

1) 3/4 to full throttle
2) Start to hear a knock or rattle sound
3) Start to see some light smoke pop out the back (Robot said it looked grey, hard to look back while at full throttle)
4) Rattle can go on for 5 seconds sometimes, other times it happens for 1-2 seconds
4) Soon as the knock/detonation/rattle sound stops, smoke goes away

There is no correlation to whether the engine was just started cold or warm, of if it's been running for an hour. Usually happens under high acceleration depending on if the engine is chugging in a low gear or revving high (not the typical coil failure behavior).

I know I have a noisy injector in there somewhere because it quiets down with some top-end fuel treatment like Lucas. So I am thinking it's a few things

1) Injector getting stuck open or not firing right
2) Cam advance mechanism isn't doing it's thing right
3) Knock sensor is garbage
4) O2 sensors are garbage and the ECM doesn't really know what's going on
5) Bad coils/plugs somewhere (Using the accel coil conversion)

One interesting thing to note is that it always kind of did this even before I did the coil conversion. It has just gotten more reoccurring lately and lasts longer. The smoke thing is new and probably popped up in the last few months.

Any ideas?

 

[fudge12]

Timing chains? Jumped timing? What engine and year?

 

[Kumba]

Timing chains? Jumped timing? What engine and year?

2006 3.9. Car runs fine pulls hard other then the above mentioned problem. I would think a bad timing chain or one that jumped timing would run rough. This still idles smooth.

 

[LS4me]

I don't know if this is the same, but both my '06's ping in that situation. Doesn't matter where I buy gas and I've run countless bottles of cleaner (Seafoam, Marvel, ChemB12, etc.) through and it doesn't matter. This is with both the stock air box and the K&N FIPK.

 

[Kumba]

Yeah I run Shell 93 pretty much exclusively from all over the place and it doesn't seem to make any difference. I guess I could try some race gas and see if that's the issue.

It just doesn't sound the most flattering when you are accelerating and you hear the ping and see some smoke. Sounds like it's half-way normal though.

 

[Telco]

I would rule out the O2 sensors as being the issue as cars go open loop and use a fuel map under WOT conditions to control the fuel/air mix, not the O2 sensors as under WOT the engine needs to run a bit more rich and regular O2s won't read right. However, the engine does still use the MAF, MAP and TPS inputs to tell the computer what cell in the fuel/air and spark maps to use. The computer also uses the knock sensors to make sure timing isn't advanced too far, but knock sensors don't usually fail without setting a code. Might also try cleaning the MAF, MAP and throttle body, and changing the air filter and fuel filter. A plugging fuel filter can cause the engine to lean out under high demand situations which can cause pinging. If you suspect a problem with the variable valve setup, pour a quart of Marvel Mystery Oil into the oil crankcase, drive the car easy for 50 miles or so, then change the oil. The Marvel thins the oil out a bit which is why you want to drive it easy, and it will clean any gunk out of the oil passages and perhaps free up any stickiness in the variable mechanism. I've used this to clean out new to me used cars before and I've actually had lumpy oil come out of these engines the first couple of oil changes when cleaning the innards with Marvel. I recommend doing this anyway as it will keep the inside of the engine clean. High temps can also cause pinging, and we all know that the LS temp gauge is just this side of worthless because it won't register an overheat condition until it's way too late. It's possible that this is your car's way of telling you that the cooling system needs to be replaced.

Hope this helps.

 

[Kumba]

Ehhh, i'm not a big fan of oil additives like Lucas or Marvel or Seaform. My major concern is it taking an already marginal seal on a 100K-mi engine and making it start to leak oil. Also had bad experiences with sludge sticking the pressure by-pass open in an oil pump before.

I don't have any coolant loss going on really. It is due for another flush though and I need to slap a new set of filters on it so I'll do that and see what I get.

I'll leave my OBD2 adapter plugged into the car and whenever I hear the noise I'll fire up the app and see what temp and timing it's at. Maybe I can figure out something from there.

 

[04_Sport_LS]

Kumba,

Sounds like spark knock/detonation, caused by over advanced timing, (either mechanical or electronic). Option 2 would be carbon build up on the pistons, or excess oil being sucked from the intake manifold at WOT, due to the PCV system design, (or lake thereof), of this engine.