Something to argue about
11-15-2018, 01:29 PM
#1
Something to argue about Have an 06 I bought with 123k on it. When I bought it, it had minor piston slap that seemed to gradually get worse. It got to the point that I considered selling the car. But then...
The crank sensor went out. Replaced sensor and now the piston slap is back to the level it was when I first bought the car.
No, I’m not crazy...but I am pretty happy about it!
Thoughts?
PS...the car has 143k on it now and I made no other changes. The crank sensor is the only thing I did to it. There were no signs of damage on the sensor.
Only thing I haven't done is the crank relearn on it so maybe it’s operating on a different timing curve or something? I have no idea but the car runs better than it has in a long time...not that it ran bad before, just pulls better and idles a little smoother than it did leading up to the sensor failure.
Almost hesitant to do the crank relearn but the CEL is on and it won’t pass inspection that way so it’s going to happen at some point.
The crank sensor went out. Replaced sensor and now the piston slap is back to the level it was when I first bought the car.
No, I’m not crazy...but I am pretty happy about it!
Thoughts?
PS...the car has 143k on it now and I made no other changes. The crank sensor is the only thing I did to it. There were no signs of damage on the sensor.
Only thing I haven't done is the crank relearn on it so maybe it’s operating on a different timing curve or something? I have no idea but the car runs better than it has in a long time...not that it ran bad before, just pulls better and idles a little smoother than it did leading up to the sensor failure.
Almost hesitant to do the crank relearn but the CEL is on and it won’t pass inspection that way so it’s going to happen at some point.
Last edited by ls1247; 11-15-2018 at 01:41 PM.
11-19-2018, 09:41 AM
#2
Try a HARD CORE engine decarb: Seafoam or GM top end engine cleaner, may have to repeat or soak overnight. I've seen this reduce or clear piston slap more times than I can count...especially when it's a cold start symptom that improves when warmed up.
11-19-2018, 03:01 PM
#3
Considering how easy it is to access, I'd consider pulling the heads to do a full decarb. But maybe that's overkill. I ended up doing it at 104k to get a exhaust bolt out of the rearmost position, so I had a little less of an option. It definitely made me feel better about the cleanliness of the internals. However, the 80k+ I've put on it since has probably gotten it back to the way it was.
Last edited by BudRacing; 11-19-2018 at 03:11 PM.
11-20-2018, 08:33 AM
#5
Piston slap sounds a good bit like knocking or detonation. It was VERY common on LS engines for a while. Eventually, they revised the skirts and coated them and it drastically reduced it. Basically, carbon buildup causes the pistons to rock just a bit, especially when cold. The rocking or slapping causes a ticking or knocking sound but often subsides or goes away completely when warmed up. This is typical but it can remain in some cases. I worked in a Chevy dealer back in the early-mid 2000s and saw it ALL the time. Between decarbs and injector flushes, I had no idea a maintenance procedure could fix so many actual problems (piston slap, misfires, etc.). Seafoam is a good solution as is GM top end engine cleaner, and BG services work great too. It was most common in the 6.0s but we saw it in all the GenIII LS engines at some point. Do it every 30k or so along with a PROPER injector flush. https://www.youtube.com/results?search_query=6.0+piston+slap
11-22-2018, 03:14 PM
#7
I'm hesitant to do the engine de-carb gig as, in my opinion at least, it can be hard on converters. And while it makes sense to do it on some level, the noise isn't that bad at this point so I think I'll spare whats left of my convertors that sort of punishment. If convertors were cheap, readily available and I wouldn't fear broken bolts trying to replace them, maybe I'd give it a go but the car runs too good and I'm too lazy to take chances with it at this point!
I just found it strange that the pitch and the tone of the noise changed when I put the new sensor in the car. Maybe it has something to do with a different base timing setting cause by slightly errant crank sensor reading or who knows whatever but I'll gladly take the improvement.
Happy Thanksgiving!