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Deville Spontaneous Engine Stalling


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My dad drives a '97 Deville Concours with about 125k on it. The car physically looks almost new, and drives like a dream.

Just reciently it started spontaneously stalling out while idling (or nearly idle... any time the foot is off the gas). It doesn't happen very often yet, and seems to have no descernable pattern. There is no rough idle before or after, it's almost like I shut off the key, and the car fires right up after it stalls. No error codes are thrown. I am familiar with how to check and reset them using the Driver Information System. There are a number of history codes, but no current ones.

We have checked fuel pressure as the car stalls, and it goes up slightly and smoothly (without any interuptions or jerks) as the car dies. We understand the slight raise is due to the pressure regulator working properly.

The output lead from the ignition relay maintains 12+ volts as the car dies.

Cleaned the contacts on the Ignition Relay, Fuel Pump Relay, and Fuel Pump Fuse.

Changed the spark plugs a little less than a week before, putting in the OE AC Delco Platinum tipped plugs (he had put Bosch Iridiums with quad platinum grounds about 30k miles ago, but they weren't putting out the same power anymore... slight oil fouling from the #7 cylinder, otherwise only normal wear observed). We disconnected the battery for about half an hour for the operation, though I don't think that should have caused anything like this.

Not sure what else to add. Thanks in advance!

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That sounds like the classic symptoms for "Crankshaft Position Sensors."

There are two of them.

They are not too hard to replace and are relativity inexpensive.

There are several threads on the board with step by step direction for replacing them.

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It could be a sticky IAC stepping motor but I believe that usually throws a code when it sticks. Cleaning the throttle body sometimes fixes that.

Another component that can cause stalling with no codes is a bad fuel pump. This rarely happens after the first few year, though, because the main thing that causes this is a bad connector joint at the fuel pump, and if it makes 30,000 miles then you don't have the problem.

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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It seems to me that he did clean the Throttle Body. I think I missed that when I posted before. My bad. <_<

He just replaced the fuel filter right after I posted, just since it hadn't been done. He decided that it wasn't the fuel pump.

CPS... I hadn't thought of that... but... wouldn't that throw a code? My car had identicle symtoms at one point right after I got it, but I traced it to the aft O2 sensor (although that DID give me a code). Hasn't done it since. I do love happy endings... ^_^

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Crank sensors sometimes won't set a code

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Crank sensor failure is common in a short range of model years beginning with 2000 but rare in the 1993-1999 model years. Of course, that doesn't mean that it doesn't happen at all. But, since you can get both of the sensors plus new O-ring seals for about $80 from Rock Auto, this might be a case where throwing parts at an intermittent problem does make sense, particularly if you install these parts yourself. First I would inspect the wiring and connectors, though, to make sure that they didn't get unduly jostled lately.

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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I really wish he would get his own username and get on here to do his own talking... :angry: He knows exactly what he's doing much better than I do. Oh, well.

I believe he gave the wires a quick once-over, but not a major one. He has the HO version, so I guess the oil cooler lines are in the way of the Crankshaft Position Sensors. He thinks that the Ignition Control Module might be at fualt. Sooooo... He wants to borrow mine for a while in a straight-over swap. The idea is this: if his car works properly now... while mine starts randomly dieing.... we found the problem. :yupi3ti: Haven't made the swap yet, as both of us our running around all over the place it seems.

Thanks a bunch for the responses folks, this ain't over yet!

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  • 3 months later...

THE SAGA OF THE 97 CONCOURS CONTINUES... I'm captain hepps dad. We swapped coil packs between my 97 and his 93 Eldorado. Both cars run fine, except he might be taking a 5%mpg penalty. My 97 runs great. What we cannot figure out is why his car doesn't have the intermittent stalling problem like mine did. I also got another coil pack from a wrecking yard. When installed on my car, I get stalling again. On his car, it runs fine (not sure yet if mpg is affected...). Thot about replacing the crank sensors, but on my car, the oil line leading to the cooler and the associated oil filter support hardware make it very difficult. Of course, if the problem is the crank sensor, why does the car run fine with the 93 coil pack? My only guess is that the 97 coil pack requires some signal from some sensor or whatever that the 93 doesn't (the 93 being older, may have a less sophisticated emissions package). Any ideas? I'm a mechanical engineer and I'm baffled...

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Link to Rough, Unstable, or Incorrect idle and stalling diagnostic chart:

http://caddyinfo.com/wordpress/?page_id=1595

just in case it prompts something you have not already thought of.

:welcomesmiley:

Bruce

2023 Cadillac CT4-V Blackwing

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