CT5-V Blackwing preignition / pinging

[sicoo]

I doubt there would be a TSB forthcoming because I haven’t heard of this problem in the LT4.

Most likely there is something wrong with your build specifically.

If this was happening to me, I would not track the car until resolved. I would locate a reputable tuner shop ASAP and get some logs done. Really surprised that amount of audible pinging isn’t setting a CEL. The OEM knock sensors are Uber sensitive for exactly issues like this.

I was thinking the same thing, which makes me think it's either bad knock sensors or incorrectly installed knock sensors. If that was the case, the ecu would have no idea about it.

 

[Neveready]

I lit the tires up at 80 on the freeway in 4th gear at half throttle and got the car a little sideways

Sorry your having these issues, you've had a rough go with your blackwings. I'm curious to see what a tuner would see at WOT. Hopefully this issue will be solved soon, a new engine is way worse than a trans swap

 

[99sport]

Tried again today. This time with half 91 and half 101 for 96 octane mix. With the cold weather this morning it was difficult to use full throttle, but once the tires got warmed up I managed a half dozen WOT pulls into the rev limiter in 3rd during 40 miles or so of driving. The car pulled to the rev limiter at WOT every time with absolutely no issues (ie no audible knock).

I also found a station that has 101 octane at the pump for $10/gal that is only a few miles from my house, so it's feasible I could run 96 octane all the time. I was feeling pretty good that I at least had a handle on what is going on (preignition knock fixed with higher octane fuel in the tank and that I am NOT crazy). Then someone wouldn't let me merge on the freeway so I used maybe 75% throttle in 6th at 80mph and had a knock even with 96 octane. The knock wasn't nearly as bad as what I was getting before at full throttle on lower octane, but maybe running 96 octane isn't a feasible fix. On the one had, it could be argued I was lugging the car in 6th, but on the other, a car with 600ft-lbs of torque should be able to pass an economy car at part throttle without a downshift without harming the engine.

I'll stew on this for a while.

 

[99sport]

a new engine is way worse than a trans swap

Yeah, I wish I had kept the first car. It had way more than it's share of issues, but it drove perfectly. The biggest concern was not having confidence the trans bolts were actually tight as it's impossible to reach them without dropping the subframe.

The last car had a lot of paint issues and terrible panel gaps, plus the issues from the trans replacement, but it drove absolutely perfectly. This car has very, very good (for a production car) paint, and mediocre, but tolerable panel gaps, but an engine that knocks under load, a very loud pulley whine (that I think might be the blower pulley since it varies with throttle / engine load / manifold vacuum), a creak / rattle from the plastic trim around the HUD hole, and a rattle from the passenger seat. As long as I can get the knock fixed before melting a piston, I think everything else can be sorted pretty easily, but, yes, I am dreading a possible warranty engine replacement due to this knock if it doesnt get figured out.

 

[MookdocOE]

Yeah, I wish I had kept the first car. It had way more than it's share of issues, but it drove perfectly. The biggest concern was not having confidence the trans bolts were actually tight as it's impossible to reach them without dropping the subframe.

The last car had a lot of paint issues and terrible panel gaps, plus the issues from the trans replacement, but it drove absolutely perfectly. This car has very, very good (for a production car) paint, and mediocre, but tolerable panel gaps, but an engine that knocks under load, a very loud pulley whine (that I think might be the blower pulley since it varies with throttle / engine load / manifold vacuum), a creak / rattle from the plastic trim around the HUD hole, and a rattle from the passenger seat. As long as I can get the knock fixed before melting a piston, I think everything else can be sorted pretty easily, but, yes, I am dreading a possible warranty engine replacement due to this knock if it doesnt get figured out.

To be honest? BMW or some other overpriced German heap will be the only thing that satisfies you.

 

[sicoo]

Yeah, I wish I had kept the first car. It had way more than it's share of issues, but it drove perfectly. The biggest concern was not having confidence the trans bolts were actually tight as it's impossible to reach them without dropping the subframe.

The last car had a lot of paint issues and terrible panel gaps, plus the issues from the trans replacement, but it drove absolutely perfectly. This car has very, very good (for a production car) paint, and mediocre, but tolerable panel gaps, but an engine that knocks under load, a very loud pulley whine (that I think might be the blower pulley since it varies with throttle / engine load / manifold vacuum), a creak / rattle from the plastic trim around the HUD hole, and a rattle from the passenger seat. As long as I can get the knock fixed before melting a piston, I think everything else can be sorted pretty easily, but, yes, I am dreading a possible warranty engine replacement due to this knock if it doesnt get figured out.

There's a guy on here (American Airlines pilot I believe) who had his engine replaced and everything worked out fine in the end. Through Sewell I believe and took only three weeks.

I'm afraid damage may be done by now.

 

[sicoo]

Yeah, I wish I had kept the first car. It had way more than it's share of issues, but it drove perfectly. The biggest concern was not having confidence the trans bolts were actually tight as it's impossible to reach them without dropping the subframe.

The last car had a lot of paint issues and terrible panel gaps, plus the issues from the trans replacement, but it drove absolutely perfectly. This car has very, very good (for a production car) paint, and mediocre, but tolerable panel gaps, but an engine that knocks under load, a very loud pulley whine (that I think might be the blower pulley since it varies with throttle / engine load / manifold vacuum), a creak / rattle from the plastic trim around the HUD hole, and a rattle from the passenger seat. As long as I can get the knock fixed before melting a piston, I think everything else can be sorted pretty easily, but, yes, I am dreading a possible warranty engine replacement due to this knock if it doesnt get figured out.

@99sport, what's the status of your engine knock issue?

Mine went away starting with the first fill up after replacing the gas from the dealer, confirming they put low octane gas in it.

Seems to run perfectly now with exception of tiny lumpiness at lower rpms and larger throttle openings, but that may be my paranoia. I think most wouldn't even notice it.

I'm still pissed at the dealer for being so stupid, risking engine damage on an expensive new car to save $15.

 

[99sport]

I have 2000 miles on the car now and there has been no change or improvement. I try to buy gas from a different gas station each time I fill up, but it has not made a difference. It is worse some days and better others (but always present, just more or less). I think it is related to the weather (and not inter-cooler or engine temp) as it seems to knock it whether the car has been running for 10 minutes or 2 hours. I have not done enough experimenting with WOT pulls at 115 mph to figure out the correlation with temperature, but I am convinced it is noticeably worse when the humidity / dew point is low. Also, I live a few feet above sea level. It is also knocks worse going up a steep hill.

I have both a WOT high RPM knock and a part throttle high-load (ie high gear) knock. The WOT knock is completely cured with 96 octane fuel. The part throttle knock is better with 96 octane but still present. However, I can easily fix the part throttle knock by shifting down a couple of gears (ie it would probably never be noticed in an automatic).

I found a recommendation for a local LT4 tuner and visited him. He is affiliated with a dyno shop, and I thought he would put the car on the dyno and really load the engine up to get it to knock. When I got there, there was another car on the dyno and we went out on the street. I did a number of 115mph pulls before deciding that was all the risk I wanted to take. The car knocked as little as I've ever experienced. It knocked from 6300-6500 rpm only.

He used the latest (gen 3) hardware from HPtuners. This was the first global B car he had seen. He said he could read A/F ratio and that it looked "good." When I asked for a number he said he would have to calculate it (I never got a A/F number). He was unable to read knock sensors or misfire data. He suggested I shift earlier and not worry about it. However, his personal (tuned) LT4 exploded 3 days before I visited, so our risk tolerance does not appear to be the same (I forgot what he said came out he side of the block). I thought maybe the problem was gone / a whole lot better, but the next morning, on the exact same tank of gas, it knocked like crazy (from 5000-6500).

I think I am going to have to go to the dealer and see if they can send me home with a data logger since I am pretty sure it is going to be against policy to repeatedly go 115mph on a test drive. I just haven't gotten my courage up enough to let the dealer work on the car.

Incidentally, the fuel cutout seems to be at 6500 as the highest revs the car recorded was 6550 - I was surprised as I had a Honda with a 7200 rpm redline but an 8000 rpm fuel cutoff. On a Honda, the redline is merely a "recommended shift point" and most Hondas (except the AP1 S2000) will happily rev hundreds of RPM past redline before the fuel cutoff kicks in.

 

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[Neveready]

This knock has been going on for 2k miles. Have you changed the oil yet? If possible, you should do it yourself so you can see what kind of damage was done with an oil analysis. I would imagine it would show up in the bottom of the pan or shimmer in the light.

 

[99sport]

This knock has been going on for 2k miles. Have you changed the oil yet? If possible, you should do it yourself so you can see what kind of damage was done with an oil analysis. I would imagine it would show up in the bottom of the pan or shimmer in the light.

Changed the oil at 600 miles. It looked fine. I haven't sent the sample in to Blackstone yet. I have a bunch of prepaid labels I cant find - and have had too much going on lately to find them.

 

[jbawden]

Is there any chance it's something other than preignition? It just seems really unusual that you're having this issue and 96 octane doesn't really cure it. If it really is preignition, I wouldn't be driving it until I could get proper equipment to data log.