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Trembling at idle

182K views 525 replies 136 participants last post by  goofygoober 
#1 ·
My 2.0T has a tendency to tremble at idle. I've switched to premium gas with no results. Also it doesn't alway happen, very irregular. Any ideas?
 
#166 ·
Hoosier daddy. I have posted numerous issues on this car. How long a test drive you need at approximate 500 miles it starts this issues I take it back because I sir have had many a new car and o by the way own a 57 Chevy 283 engine and it far smoother than this 40k car.i have gone thru the proper channels right thru to the district man for cadillac.you may like to drive your car with trembles and shakes that's your decision.i had a pt cruiser for 11 years and never experience anything like this.sonas a cadillac owner and a way step up to this car I expect better and not expect anything less.i have had a personal chat with service mgr and he assures me that the turbo now is smooth and he got one for his wife.so I think cadillac can either fix there 2.5l. Or step up and get me into a turbo. The quality I deserve since I pay the bill.i am sick and tired of customers excepting inferior cars from our American company's we deserve better and GM needs to assure us no matter if we test drive a car or not. They should have quality tested this engine not just throw it out there and we the consumer suffer.
 
#168 ·
I experienced the tremble a few times but not any in a while. I had my oil changed at 1000 miles and sense the change no issues with idle. It's got a bit warmer here but still very cold in the AM. I have even stopped warming my car up while I get ready for work and just go out, start and go. No issues at all.

How many that have the issue have yet to do their first oil change? Maybe it will help? I try to do my first one around 600 to 1000miles because I'm old school and that is how I have always done it.
 
#170 ·
I have had this happen in my 2008 CTS 3.6 a few times a year, it's starts to tremble feels like it will almost stall, then after about 15 seconds its right as rain. I never thought of it as a problem because it happens so infrequently.
 
#171 ·
Tony,

Like you I have a 2008 CTS 3.6DI but I have never noticed a stall or tremble at idle. Fairly consistently from a cold start after a few seconds the fast idle RPM will start to drop and then immediately revert to fast idle before waiting a few seconds and then starting to drop in steps to base idle. It isn't really a problem but this little glitch is very noticeable and it does make the engine control system seem a bit incomplete. For those who start the vehicle and immediately put it in gear it probably isn't noticed but I like allowing the engine to warm enough to reduce idle speed before shifting out of park.

It is an entirely different engine but by comparison the 6.6 turbo diesel in my 2006 GMC Sierra is quite a bit smoother and just about as quiet. A nice thing about the diesel is it doesn't need to fast idle from a cold start and the only time it does is when the temperature is below 28 or so and it utilizes fast engine warmup strategy. It starts at normal base idle and after 30 seconds begins slowly ramping up to a 1,200 RPM fast idle in 50 RPM steps. The variable vanes in the turbocharger are simultaneously moved to increase back pressure and the transmission output shaft is locked but the input is loaded to also put more load on the engine. It works very well for fast warmup although it sounds like a little jet engine during this strategy. As the temperature increases the idle RPM begins to ramp downward and drops to base idle as soon as the brake pedal is touched. Obviously some pretty well thought out programming went into this process and it would be nice if the 3.6DI was as sure and solid during its initial cold RPM control.
 
#173 ·
Nice to know it is consistent across the 2008 CTS :) I had the flash to revise the oil life calculation but otherwise it is the original software. The only real annoyance I had with mine is I have a late production 2008 which came with bluetooth and when the OnStar module was recalled and replaced the dealer used the earlier module even though I specifically noted on the service order mine was bluetooth enabled. The first response was that they forgot to "flash" the new module and of course it still didn't work since it wasn't the correct module so for the third trip for this supposedly simple recall I wrote an explanation using mostly single syllable words and they finally ordered and installed the correct module.

Prior to this the dealership has provided excellent service over a 20+ year relationship but this was not a stellar service encounter.
 
#178 ·
My 2.0T idles at 700 rpm, and has stalled 3 times today alone. my car has 150 miles on it. its very hot here in nyc and it stalled 2 times at a red light with ac on full blast and once while filling my car with gas. My car is a manual tranny. Not sure what to do. if it continues i will bring it in.
 
#181 ·
Hello CADILIKENYC,

I apologize for any inconvenience you are experiencing with your ATS. I understand how this can be frustrating, after having recently purchased the vehicle. If you would like to further discuss your concern, please reach out to me via private message and include your contact information and VIN.

Laura M.
Cadillac Customer Service

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I currently have a data recorder from GM installed for random stalling that has increased to a couple of times a week during decel or stopped at a light. I'm hoping to have an answer in the next couple of weeks. Apparently GM is shut down for the next 2 weeks or something during the holiday.
Hello bungee91,

I am sorry your ATS is experiencing a random stalling issue. If you would like to discuss your concern, please reach out to me via private message so we can further interact on your current situation.

Laura M.
Cadillac Customer Service
 
#180 ·
I just got my 2014 ATS yesterday. It was one of the first ones off the 2014 assembly line which started production on June 10. It was 110 degrees here in California yesterday, and I took it for a test drive. Started it up, put the A/C on full blast, and went to some stop lights and stop signs to try to get it to stall. It was perfect. I also really hammered it down when pulling out of one of the stop lights. It was perfect; no problems at all.

My 2014 was idling at 750 RPMs.

There is NO vibration at all in the cabin. I popped the hood and put my hand on the top of the engine (surprisingly HOT) and I could feel it vibrating somewhat. However, this vibration was completely isolated/damped out before getting to the cabin.

If someone says vibrations are "normal" in the cabin of the car, they have not driven a nice ATS.
 
#182 ·
Noticed my 2.5 does it also. Most noticeable when I first start driving the car. Once the car is warmed up-almost never notice it. Mentioned it when it took it in for service and was told the engine was set to spec. so I guess that means everyone does it. Never got so bad that I thought the car was going to stall.
 
#185 ·
Ugh, Sorry man. I will admit I had the issue the other day with the AC on. Just a quick stumble but a stumble just the same. Hopefully they will come with a fix. When it happened I gave a tad bit of gas and it went away. Let off and it came back so that tells me it's an idle issue and simply needs to be upped a bit. I noticed that when it did this it was idling around 500 which it normally does around 700.
 
#187 ·
These VVT GDI engines are very different animals than what we have grown accustomed to over the past 25+ years of SVT MPFI being commonplace in most engines. So naturally they will behave differently while performing as they were designed. Increased fuel economy and HP, more evenly distributed torque, and lower gaseous emissions are the benefits of this new generation of engines; but these benefits are offset by rougher idling, more noise, and increased solid emissions in the form of soot. I am sure over the next decade most of these issues will be conquered.

I am not saying that everyone complaining of rough idle is unfounded, but I am sure some people think something is wrong since the VVT GDI is noisier and rougher running than their old SVT MPFI's. After all, it does seem backwards that a better engine would act like a worse engine on the surface!

BUT I have read on Lexus forums and Hyundai/Kia forums that there have been problems with sticking Oil Control Valves (OCV) even in brand new cars that have caused abnormally rough idling issues. At low rpm, overlap in open intake and exhaust valves should be minimal or zero. At higher rpm, the VVT allows the overlap to grow which is the beauty of the VVT. If the OCV sticks and doesnt allow the overlap to close out, low rpm stability can be adversely affected, even without throwing any codes. These faulty OCV's were replaced and problem was solved. It is a shot in the dark really for our Caddy application, but could be a culprit here!

Below is a quote from an article on what the OCV does in the GM 2.5:

"Impala’s 2.5L engine, which delivers SAE-certified 196 horsepower (146 kW) and 186 lb-ft of torque (252 Nm), achieves variable valve lift using an all-new rocker arm that switches between low and high lift intake cam profiles. The mechanism is actuated by an oil control valve through a dual-feed stationary hydraulic lash adjuster. It is the first of its kind for low friction roller-type finger-follower valvetrains in gasoline engines. The engine’s computer continuously selects the optimal lift profile based on conditions such as engine speed and load."

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...point being that if too much valve overlap is present at low RPM, exhaust from the open exhaust valve travels into the intake thru the open intake valve and mixes with the incoming gulp into the cylinder. The extra CO2 and CO in the incoming gulp causes an erratic rich mixture and too much fast variability for any buggy computer (not just Caddy) to keep up with compensations for a sticky OCV. Just saying it's a solid possibility.
 
#191 ·
Everything you just read applies to the turbo and 3.6 as well. All indications point to the problem being as likely or more likely with the turbo as the 2.5.

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Interesting you say that because both service mgrs said that the turbo is completely different engine. Geez what's going on!i have test driven about 5 turbos and find not rough at stop lite a little vibration in park but nothing like the 2.5. Two different dealers same answer. What's up with that
Of course they are different engines. But they have the same characteristics that cause the roughness for SOME of the motors.

The fact that you found 5 turbos that were smooth is no surprise. You could drive fifty 2.5s and all could be smooth. I have to assume even your 2.5 didn't run rough when you test drove it. If it was rough then, you were happy enough with it to buy it. If it started after you bought the car, why would you think any other one that was smooth when you drove it wouldn't develop a roughness later?
 
#193 ·
Yes that's correct I had a short test drive up and down the highway and back to the dealer but didn't experience the rough idle.if I had known about these forums before I test drove I would have done the stop lite and sit there test but not the case.i assumed that cadillac had produced a supreme car.i shouldn't have to go looking for issues. Haven't had to do that with my other cars.trying hard daddy to assist with a resolution that's my goal also nothing less.i haven't been on any forums because my other cars had no issues. What's up with that lol
 
#194 ·
Muffin said:
Interesting you say that because both service mgrs said that the turbo is completely different engine. Geez what's going on!i have test driven about 5 turbos and find not rough at stop lite a little vibration in park but nothing like the 2.5. Two different dealers same answer. What's up with that
They in fact are different engines- different displacement and aspiration, and probably many other details as well. So the dealers are not wrong. But all 3 engines have the same variable valve timing and direct injection technologies. Almost all car companies have already made the switch to variants to these technologies with their complete lineups. This is not new.

If I was a dealer, I would change out your OCV and OCV solenoid to see if that fixed your issue. Cheap parts and not a major repair either.
 
#201 ·
Just received call from dealer claims GM now has the software fix for the trembling engine update of ECM. Can Greg and or Laura please confirm that this is true. Just need reassurance that this has come out from your view point. Thanks

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Hey daddy can you confirm that as of today GM has given the software updates to dealers about the trembling motors appreciate any info you can provide
 
#202 ·
Just got the call from my dealer. According to my service consultant, there is now a fix for this issue for the 2.5 engine and everyone who has this engine is going to be contacted by phone or mail. My appointment is a week away on the 8th. I'll let you know how it goes.

Now -- if they can just find the cause of my intermittent electrical ground issues.
 
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