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Simple engine miss causing MANY problems


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The wife and I took our next door neighbors to dinner Saturday evening. The place is only a couple of miles away, so the Caddy's engine didn't even begin to get warmed up. When we were ready to leave, I used the remote starter to get the car cooled down before we got in. The neighbor was commenting on how nice the car was when everything went to crap. The engine started missing, the Check Engine light came on, The "Traction Control Disabled" flashed up on the DIC, alternating with "Service Stabilitrack System" and the transmission started shifting hard! I'm thinking to myself "what a way to make an impression on my (attorney) friend that told me that he hasn't owned an American car since a 1959 Ford, and that they were ALL JUNK!"

Anyway, I took the car to the dealership yesterday (Monday) and they called me about two hours later, telling me they fixed my car! #6 spark plug was shot, no other issues! I was certainly surprised that all of those issues and warnings could be the result of one bad spark plug. Can anybody explain why all those things (of course I understand the check engine light) were the result of a miss?

Never underestimate the amount of a persons greed.

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A selection of OBD codes would help here. The reason that we need the codes to properly answer your question is that the PCM operates the digital fuel injection (DFI), spark, and transmission using data from a whole bevy of sensors, from throttle position to intake air temperature. The transmission has no vacuum modulator to control the shift firmness like mechanically controlled transmissions, for example - that function is served by the MAP sensor in the intake manifold, and it is supplemented by transmission input speed and other internal sensors along with engine data including a running computation of engine torque and RPM, and the transmission is controlled better than any non-electronic transmission could possibly be managed through this PCM programming which operates the three transmission solenoids through PWM signals that control which solenoids are actuated and how gently or strongly.

I suspect that you first threw a P0300 (at which time the MIL comes on) and then the HO2 sensors started throwing codes because of problems in the exhaust gases or little backfires or some such. In any case, the miss apparently caused your DFI to go into a default open-loop mode because something essential to closed-loop operation, like the HO2 sensors, weren't meeting requirements to properly support closed-loop operation. Once the engine goes to open-loop mixture control, operation of the transmission goes to a default mode. The default mode is a little rougher than an analog transmission because it's designed as a get-home-and-call-your-dealer-for-a-service-appointment thing, not a general-purpose driving thing, and firmer shifts are easier on your transmission under the widest set of possible driving conditions, all things considered.

Not that without the OBD codes I am really guessing here.

Please let me offer a suggestion for you and your lawyer friend. Organize a tour of dealership service departments, timed when they are working on at least one high-end car such as an Avalon or Lexus 400 series or BMW 5 or 7 series or Mercedes high-end, perhaps a BMW M-series or Mercedes AMG. Also do the same tour under the same conditions at a Cadillac and at least one other GM marque, such as Chevrolet or Buick. You migth want to do the same for Ford and Chrysler if you like. Look for internal engine work or for extensive diagnosis and repair involving the networked modules that run the car. Compare what you see in the quality of the innards of these cars, all of them. Separately, compare the skill, training, specialized diagnostic tools such as the Tech II and skill of the techs in operating them, competence, and rate of progress on repairing the cars that you observe. Do that, and all mystique of black-box import cars will evaporate. Nobody on Earth produces better drivetrains than the Americans, and, in truth, never have. In the 21st Century, nobody on Earth trains its service people better than GM, and, possibly (I have no direct knowledge but have heard good things) Ford. Chrysler was once in that league (1970's) but I have no direct information for too many years to say anything.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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Jim...

One tiny small correction here...

It doesn't affect your diagnosis... (which I agree with)...

But starting in 2006, the DTS has a separate Transmission controller.

They now have two control modules...one for the engine...(ECM or Engine Control Module) and one for the transmission.. (TCM or Transmission Control Module)

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The wife and I took our next door neighbors to dinner Saturday evening. The place is only a couple of miles away, so the Caddy's engine didn't even begin to get warmed up. When we were ready to leave, I used the remote starter to get the car cooled down before we got in. The neighbor was commenting on how nice the car was when everything went to crap. The engine started missing, the Check Engine light came on, The "Traction Control Disabled" flashed up on the DIC, alternating with "Service Stabilitrack System" and the transmission started shifting hard! I'm thinking to myself "what a way to make an impression on my (attorney) friend that told me that he hasn't owned an American car since a 1959 Ford, and that they were ALL JUNK!"

Anyway, I took the car to the dealership yesterday (Monday) and they called me about two hours later, telling me they fixed my car! #6 spark plug was shot, no other issues! I was certainly surprised that all of those issues and warnings could be the result of one bad spark plug. Can anybody explain why all those things (of course I understand the check engine light) were the result of a miss?

JohnnyG,

I can't see how a bad spark plug could create so many problems. For the heck of it I would unplug #6 plug wire for a minute or so and see what happens. Unburned fuel is not good for cat converters, so I would not leave it like that for more than a minute.

What really raised a red flag in your post is that remote starter. They can create all kind of electrical problems under certain conditions.

Next time you take your neighbors out, rent a Ford! :D

The saddest thing in life is wasted talent

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Anyway, I took the car to the dealership yesterday (Monday) and they called me about two hours later, telling me they fixed my car! #6 spark plug was shot, no other issues! I was certainly surprised that all of those issues and warnings could be the result of one bad spark plug. Can anybody explain why all those things (of course I understand the check engine light) were the result of a miss?

Color me skeptical.

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I suspect that you first threw a P0300 (at which time the MIL comes on) and then the HO2 sensors started throwing codes because of problems in the exhaust gases or little backfires or some such. In any case, the miss apparently caused your DFI to go into a default open-loop mode because something essential to closed-loop operation, like the HO2 sensors, weren't meeting requirements to properly support closed-loop operation. Once the engine goes to open-loop mixture control, operation of the transmission goes to a default mode. The default mode is a little rougher than an analog transmission because it's designed as a get-home-and-call-your-dealer-for-a-service-appointment thing, not a general-purpose driving thing, and firmer shifts are easier on your transmission under the widest set of possible driving conditions, all things considered

Jims_97_ETC is, in my opinion, exactly right on this, right down to the overly rich mixture hitting the O2 sensors (smelled terrible). Unfortunately, since this is a 2008, codes are only available through onstar, if you even get somebody that will tell you what the codes are. In essence, Onstar might make an appointment for you at your local dealership...but I can do that myself.

The service log did report the P0300, and the tech went straight for that issue first. Follow up checks on all of the other reported issues were resolved as soon as the remaining codes were cleared, according to the report.

As for my lawyer friend, and the suggested project, he has owned a few BMW's and is currently driving a Toureg since it is basically a Porsch underneath. I've ridden in it and found it rather dissapointing. He purchased a CC for his wife, which I have not ridden in, but she seems to like it. It is unlikely that he will ever change his mind, much in the same way that Toyota owners won't change theirs. I'm fairly happy with my car and the dealer did a good job, so all is good. I even made $100.00 on the deal (minus the $35.47 for the new air filter that I requested) for them to remove my heated windshield washer module (Grrrrr..)!

The purpose of my post was to point out just how many codes and issues could be related to a single small problem on these cars. Thanks for the replies! John

Never underestimate the amount of a persons greed.

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Oh BTW, during my adventure I learned that programming and code reading on these cars is now done wirelesly at the dealership. I never saw that coming!

Never underestimate the amount of a persons greed.

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Thanks Jim! I really hated to part with that thing, but I had to sign off on it at the dealership so as not to hold GM reponsible. I never used it anyway. I probably will get this new unit from AlpaTherm though. I'm heading back to Florida in November and the mountains of West Virginia can have a few surprises for drivers that time of year.

Never underestimate the amount of a persons greed.

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Thanks Jim! I really hated to part with that thing, but I had to sign off on it at the dealership so as not to hold GM reponsible. I never used it anyway. I probably will get this new unit from AlpaTherm though. I'm heading back to Florida in November and the mountains of West Virginia can have a few surprises for drivers that time of year.

I probably should order one of the replacements and let GM pay for it by giving me the 100 bucks for removing the old one. :D

I used my heated washer quite a bit when I was in Florida a dew weeks ago.

It is GREAT for getting bugs off od the windshield.

Especially when the front of the car looks like this....

.

.

P5010024.jpg

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Jim...

One tiny small correction here...

It doesn't affect your diagnosis... (which I agree with)...

But starting in 2006, the DTS has a separate Transmission controller.

They now have two control modules...one for the engine...(ECM or Engine Control Module) and one for the transmission.. (TCM or Transmission Control Module)

Thanks for the heads-up. That makes a lot of sense to me. There are several functions in the older PCM's that likely mean more than two processors (PLL to keep real-time track of the crankshaft angle, look-ahead estimation of firing time to provide accurate spark and fuel injector timing, crunching from all the DFI sensors and the crankshaft speed to determine injector duration, collection of all the engine and suspension data plus the transmission data to control the transmission, control of the A/C, etc.) but the close coupling between the engine and the transmission controls made it logical to put them in the same box. We know that the knock sensor is paired with a snap-in submodule on the PCM. But most others have separate PCM and TCM modules with a dedicated cable between them. The PCM needs cooling, the TCM does not, so there is that too.

See my post #2 about car quality. For a mini-comparison, ask your service manager to take you through your Cadillac service department anytime, then, with your doctor friend with his BMW if necessary, ask for a similar tour through the BMW service department. Look for the specialized diagnostic equipment, and ask about what is done if a car develops a lifter noise or an oil burning problem during warranty - does everything just go back to Germany or the US warehouse? What can they handle locally, and what do they send to a central specialized refurbishment depot, or just scrap?

Your bumper and grille do look like they performed the function of a bug zapper over a period. My metaphor for a traveling car while I lived in Austin was a Buick with four suited men in it, with Dallas plates and a bird in the grille. I would check the A/C condenser and see if it needs cleaning, but one of the functions of the grille is to break up the air flow so that debris does not hit the condenser at high speed, so you probably can clean it with a whisk broom.

If you drive in Florida or other buggy country a lot, you might consider adding the headlight washer/wipers, if they can be added to your car.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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Thanks for the heads-up. That makes a lot of sense to me. There are several functions in the older PCM's that likely mean more than two processors (PLL to keep real-time track of the crankshaft angle, look-ahead estimation of firing time to provide accurate spark and fuel injector timing, crunching from all the DFI sensors and the crankshaft speed to determine injector duration, collection of all the engine and suspension data plus the transmission data to control the transmission, control of the A/C, etc.) but the close coupling between the engine and the transmission controls made it logical to put them in the same box. We know that the knock sensor is paired with a snap-in submodule on the PCM. But most others have separate PCM and TCM modules with a dedicated cable between them. The PCM needs cooling, the TCM does not, so there is that too.

See my post #2 about car quality. For a mini-comparison, ask your service manager to take you through your Cadillac service department anytime, then, with your doctor friend with his BMW if necessary, ask for a similar tour through the BMW service department. Look for the specialized diagnostic equipment, and ask about what is done if a car develops a lifter noise or an oil burning problem during warranty - does everything just go back to Germany or the US warehouse? What can they handle locally, and what do they send to a central specialized refurbishment depot, or just scrap?

Your bumper and grille do look like they performed the function of a bug zapper over a period. My metaphor for a traveling car while I lived in Austin was a Buick with four suited men in it, with Dallas plates and a bird in the grille. I would check the A/C condenser and see if it needs cleaning, but one of the functions of the grille is to break up the air flow so that debris does not hit the condenser at high speed, so you probably can clean it with a whisk broom.

If you drive in Florida or other buggy country a lot, you might consider adding the headlight washer/wipers, if they can be added to your car.

On the ECM and TCM...

My ECM is inside the cold air inlet tube, just before the engine air filter.

The TCM is on the firewall, right in front of the driver.

I have been thru my dealers service dept several times. :D

My service adviser, the service manager and myself have an understanding.

I have free run of the place... up to a point, but I don't abuse the privilege.

I cleaned the AC condenser the next day at a car wash... being very careful not to bend any fins with the high pressure soap and water.

I don't think it wold be possible to add the headlight washer to it, but it would be nice.

We don't go to Florida all that often, but my lights are pretty easy to clean.

I have extra heavy 3M clear film over them and I use the windshield cleaner thingy at service stations to clean the lights.

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