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Discussion Starter · #1 ·
Hey, can someone help me solve this problem with my Cts-v that has been eating me away? I recently bought a 2017 Cadillac CTS-V in September of 2020 and within the first week of owning the car, it’s never been performing or even anywhere near what a CTS-V should be. The car came with aftermarket Headers, Cat-Delete, K&N air intake, and Corsa exhaust system. Since the first week of purchasing my car has had a blown header head gasket, burned through engine coolant tank, bad spark plugs, and brand new o2 sensors blown up within 2 weeks of installation. I’ve tried everything and went to every mechanic and tune shop near me and no one has been able to solve the problem for me. I paid $94,000 for the car and am currently $3,000 into repairs and diagnostics costs with no answer. As I drive the car I notice an engine misfire as I continue to make the car go and push it a bit. It does not rev past 4,000 rpm without this shuddering noise (attached in the video below). I took it to a tuning shop and they suggested I drive the car without pushing the boost past 0 on the gauge and the car moves without a problem. The tuning shop also put it on a dyno and immediately removed it after hearing the sound it made when applying throttle. The car also on the dyno saw a knock retard of 17 degrees. Someone on this forum please get back to me with any information that could be of help, as I only drove my car 530 miles since purchasing and it hasn’t run properly since the first week of owning. Thanks also there’s no lemon law that can help me legally where I live.

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Shudder Video
 

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can u upload the tune file and log file ?
 

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Scanning the car for dtc’s or “codes” would be the first step.


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What happens when you rev it up in park? Will it go past 4k? Does it make the noise? Doesn't sound good at all....
 
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Blower doesn't sound happy at all. I'd get the blower off and have it sent to someone reputable to give it a thorough look over. Possible things are OK with essentially no load/boost but as soon as everything pressurizes you get a problem. Perhaps before doing that, I'd take the wires off and ohm them out to make sure they are in-fact all still good.
 

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OK, call me stupid, but my first instinct is that the exhaust is restricted. Pipe bent/collapsed, "cat delete" didn't work, shop wrag in a header...who knows but I would first check codes but then I would open the headers and kick it to see what happens. That video reminds me very much of plugged cats... but also of flat cams and barely operating exhaust valves.
 

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Take it to a better shop imo.

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Discussion Starter · #9 ·
Scanning the car for dtc’s or “codes” would be the first step.


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I scanned the car with several scanners and the tuning shop scanned the car also. The car seemed to have a very weird tune that did not have many engine signs existing on the tune therefore the car doesn't shoot up the exact problem signs. The tuning shop looked at the tune on the car and it had lots of weird adjustments done on it such as a slightly higher rev idle, lowered sensitivity on the o2 sensors. To sum it up the tuner told me the tune on the car is "Complete shit".
 

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Discussion Starter · #10 ·
Anybody pulled the valve covers yet? Bad spark plugs meaning they were fouled out and the o2s?
I had a mechanic swap out the spark plugs with new ones but did not fix the problem. The car has new spark plugs and o2 sensors and still has the same problem. The mechanic also suspected it was the ignition coil but upon a further look, the ignition coil was in good shape.
 

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exactly my point in getting it to a shop that can fix it instead of pointing at the obvious.

most likely alot of codes have been tuned out and wont report , masking the issue at hand . best bet is to reflash a stock tune and work from there imo. the v3's are much different when tuning compared to a v2 so make sure the shop has experience in the LT engines , not just LS.

if you could post your tune file and a log with the issue occuring , youll get some help here , without that its a guessing game.
 

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Discussion Starter · #12 ·
I've been told by a mechanic that the car is running lein but an engine code that appeared said the car is running rich. The tuning shop I visited was the best tune shop in my province here in Canada, as they've done twin-turbo builds on Lamborghini's, built 1,000 horsepower mopars and etc. The tuning shop said it could quite possibly be a problem with the engine block. Do you guys believe that? is there a chance I may need a new LT4?
 

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Discussion Starter · #13 ·
I do have a manufacturer warranty, and it expires in June. do you believe it's worth purchasing stock parts, reverting the car back to stock, and flashing it. Then take it into Cadillac with my warranty and let them figure out the problem?
 

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Sounds like you really need to get the tune fixed to report the DTC's if they have been turned off.

That noise would keep me from driving the car. $94k? That's a lot of scratch for a used car. Wish ya the best!
 
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Discussion Starter · #15 ·
Sounds like you really need to get the tune fixed to report the DTC's if they have been turned off.

That noise would keep me from driving the car. $94k? That's a lot of scratch for a used car. Wish ya the best!
Ya the value on these V3's in Canada is quite high and insane. Do you think if I flash the car to stock to see the DTC's and I have all these mods may risk further damaging my car? would it be safe to drive with a flash and stock tune as I still run aftermarket headers and no-cats?
 

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if that's the case I would verify hard parts asap. That doesn't sound good at all. botched tunes can cause all kinds of problems . I had a broken crank once that wouldn't show up until you loaded it. It ultimately wiped out a block. pull the valve covers , blower, everything you can to find the criminal component/s
 

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At the very least get the DTC's turned on.

The screenshot you posted of the datalog shows an intake MAP value of 35.9psi and a commanded EQ ratio of 14.7 with 98.8% throttle. That's nuts!!! Taking away atmospheric pressure leaves you with 25.2psi if you're at sea level which can't be right unless as Mr. Surly mentioned,,,your cats are toasted.

Does it make the noise in park above 4k???
 

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good point that scan is schizo. I'd like to play it in real time.
 

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Discussion Starter · #19 ·
At the very least get the DTC's turned on.

The screenshot you posted of the datalog shows an intake MAP value of 35.9psi and a commanded EQ ratio of 14.7 with 98.8% throttle. That's nuts!!! Taking away atmospheric pressure leaves you with 25.2psi if you're at sea level which can't be right unless as Mr. Surly mentioned,,,your cats are toasted.

Does it make the noise in park above 4k???
There are no cats in the car, to begin with. I'll data log the car today and upload the results on here ASAP. Also, I'll get back to you on the revving above 4k in the park as well. I believe when I rev the car in park, the limiter is at 4k and does not go above that. Lastly, on these forums, I saw a post about a second-generation Cts-v that was producing a knock retard at 12.5 degrees due to an intake leak and some sort of a vacuum leak.
 

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Discussion Starter · #20 ·
good point that scan is schizo. I'd like to play it in real time.
I will upload more videos of how the car acts and drives. It's quite insane since I've looked on multiple forums and other cars such as Corvettes and Camaro's that have the LT4 and have never seen anything like this. I've heard the LT4 platform and engine is "bulletproof", leading me to believe there is no way the engine block itself is shot with only 18,000 miles on the car.
 
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