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Discussion Starter · #1 ·
Hello all, this is my first post on my 2012 CTS-V Wagon. I have owned the car for 5 years with minimal issues. I have now and experienced this no power problem twice and much more severe this second time. Both times was driving up the mountains to Lake Tahoe on hot summer days. Initially, the auto transmission would studder and not want to downshift when trying to maintain speed up the hill so I would drive in manual mode and this would take care of it for a bit. Next it just would not give any power when I would push on the gas and the car would eventually come to a stop. Check engine light comes on and I stop the car. Once it rests for a bit (~20min) start it up and it will take some gas and accelerate, still downshift issue but has power back. Have noticed when it gets cool/flat it seems to get much better. No issue with engine temp and transmission temps were in the high 180's to low 190's. I took it to the dealer after the 1st time and they had no idea......

Car is totally stock, lost my OBD reader and getting a new one so will read the codes once I get it.

Thanks everyone for any ideas.
 

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That area through Sac/Folsom gets crazyyy hot on the way up—did you check the easy stuff first? HX coolant level? Verify the HX pump is turning on?


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If it only happens on long pulls up steep hills then engine is a heat issue. I would not trust the temperature gauge. The engine does go in to reduced power when it overheats (ask me how I know), but it goes out of its way to let you know when it happens. But symptomatically, what you describe is how my car behaved when it was overheating. Going up the long hill to my house, it went in to reduced power mode, and in that mode it barely had the power to make it the rest of the way up the hill. I had a rusted out hose clamp on the lower radiator hose where it met the radiator. Maybe there's some other sensor besides temperature that induces limp-home mode...

I can't think of a way fuel would produce the symptoms you describe. And if it was a lubrication problem causing something to seize, even if it loosened up again quickly, by now it ought to be busted in some obvious way.

I can maybe think of one way it could be fuel related and hill related. If you have a lot of water in the fuel tank, maybe on long pulls up hill the pickup is starting to suck on water instead of gas...
 

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I have to ask, because symptom descriptions can often be misunderstood.
You said it “won’t give any power” and also that the transmission shuddered.
When you are giving it throttle, is the engine revving up but the car is not accelerating ( as in the transmission is slipping) or is the engine staying at a low rpm?
If the engine will not rev up while driving, will it rev in neutral?
Did the dealer report any codes being stored?
I’m curious about the condition of the catalytic converters. One partially plugged cat could cause these issues and also be more pronounced under the long climb event. The same problem could effectively ‘disappear’ once back down the mountain.
Did boost pressure go high during this event?
Were there any odd noises from the engine?


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Discussion Starter · #6 ·
Hi Mr Surly,

The engine does not rev at all, I like how you asked that because the transmission is not slipping at all it's more like it won't engage but there is just no power behind it so maybe it will not go to the lower gear without the power.
When I stop and put the car in neutral the engine will rev, I should have tried this while moving before I stopped but did not.
The dealer thought it was related to a fuel delivery issue and pointed toward a circuit board, there were no codes to support this. I never felt like it was a fuel delivery issue
No high boost and no weird noises, actually all very quiet.
No idea on the cat, how would I go about looking into that?

Thanks.
 

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"Shuddering" is how the car feels in limp home mode. Every cylinder is firing on alternate cycles, only. The motor wasn't designed to run smoothly that way, and it doesn't.

That's why I think it's engine heat in spite of the temp gauge looking OK.
 

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What codes did the dealer find? There HAD to be codes set after a limp mode event or any severe non-responsive throttle issue. How dirty is the air filter? Does the exhaust sound 'normal'?
Something like a restricted exhaust or plugged cat is difficult to assess if it happens to be that.
Sometimes the exhaust will "sound restricted" which is impossible to describe, of course.
There is only the slimmest of chances that your car has these issues, but when you are grabbing at straws, you gotta grab some long ones, too.
Anecdotal:
These cases were pre-OBD so no code info.
I have seen cases where plugged cats caused the manifolds to glow 'cherry red' yet the engine wasn't overheating; there were NO indications on gauges that there was a problem while at the same time, the car couldn't go 40mph... but also wouldn't rev freely in neutral unless it was allowed to sit for a while.
A guy had a 6cyl pickup that ran fine until above 45mph where it would just run out of power, but was great everywhere else. No overheating, no timing issues. He tried plugs/wires/filters/even brakes (maybe dragging(?) and no change. At some point, while backing up he had curbed the tailpipe square-on; this resulted in a Z-bend in the pipe just ahead of the axle, that restricted the flow to maybe 3%. Replaced the pipe, ran like new.
 

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I remember my 1969 Cougar lost power going up into Vail colorado. We were at 8800 Ft. Drove all the way back to Ct. with NO issues. That was the only Blip in the trip. Perhaps it was the thin atmosphere. The motor is just a BIG air Pump. So it stands to reason. If it only happens once a year. Perhaps it needs a tune. You dont state the Mileage. Probably something stupid as always. It took me five years to find a stalling problem I had in a car. Turned out it was the temp sensor .... who would have guessed. Good luck! If it does not happen often.... I wouldn't try to recreate the wheel.
 

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Clogged cats aren't intermittent unless they're broken and moving around causing it to flow well sometimes and not others, obviously noise associated with this. I'd def say hx is low. Not sure if the coolant in the rad could get low enough for air to reach the sensor in the head, and give a false reading, without devastating consequences. I'd agree coolant temp could vary 10 to 15 degrees between the gauge and actual but I'm not sure it could get hot enough to go into limp.

Dealer was probably referring to fpcm problems, which would be easily diagnosed following command and actual pressures and voltages, and I don't see driving uphill giving fuel issues unless the gas light was on.
 

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Clogged cats aren't intermittent
Not intermittent, load sensitive.
In other words, not noticed in lighter-load cruising.


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The motor is just a BIG air Pump.
That's why our engines have Superchargers. A blown engine compensates for lower air density. It's why the P-38 Lightning was the best high altitude fighter of WWII. Its motors (P-38 had two) were supercharged for operation at high altitudes.
 

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Op says after the car cools down it runs fine. Not indicative of a plugged cat. Once a cat begins to overheat and fuse together there is no coming back.
 

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Any thoughts it could be something going on with the traction management system?
Like if trying to do a power brake burnout and engine is reduced to 1600 rpm even if the gas pedal is to the floor.
 

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There HAD TO BE codes stored if the event occurred as described, right?
Either temp related or limp mode or none-response throttle or trans related. Something should have set a code


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