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97 Deville rough startup


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Funniest thing happens to my 97 Deville. When I start the car up cold, the engine just doesn’t seem all that smooth. Don’t get me wrong, its not bad. Just not as smooth as when warmed up. That just normal? Plugs? I wouldnt say its ROUGH, just not as smooth as normal

Something else? No codes

Car only has 45,000 miles so I guess its still the original plugs and wires.

Also as a side note. After replacing hoses, thermostat and tank reservoir, the car runs a lot cooler. I would say around 6 degrees lower.

As long as I stay moving at 30 mph or above, its pegged at around 197. On the highway it can fluctuate between 190 and 197 or so. Standing still or in traffic it can go to around 212, but that does not happen often. Of course when I switch the AC on, it drops down and stays at 197 or lower even in traffic. I installed the OEM thermostat. The recovery tank was also plugged. Lot of tablet sludge in there. I just replaced it and kept the old one for a spare.

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This symptom is indicative of a bad head gasket but, it does not sound like you are having ANY overheating issues at all.

You dont say anything about whether you checked for DTC codes do you have any?, even history

Odd, but make sure your intake snorkel is tight, we recently had a member who had a miss and it was due to the intake snorkel being loose, I for some reason the 97 would be sensitive to that issue but, take a look. Ill try to find the thread, I think it has to do with a 2001 with a combined MAF and IAC

See this thread, its an O1, I dont think this would impact your 97

http://caddyinfo.ipbhost.com/index.php?showtopic=42066&page=6&hl=%26quot%3Beat+their+young%26quot%3B#entry209790

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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No temperature issues. Driving on the highway yesterday, AC off, the temp was fluctuating between 192 and 196. Sometimes dipping to 190.

I stopped the car, cleared all the codes and drove on for another 30 min or so. When I checked codes, all I got was this

NO PCM

NO IPC

NO ACM

NO SDM

NO TCS

NO PZM

NO IRC

RFA B2560

NO MSM

NO MMM

The B2560 refers to the clicker? It works fine. Whats up?

Now I have a baseline, so can check again later.

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This could be morning dampness on the ignition wires. When were your ignition wires last changed? Also, try cleaning the coil towers of any corrosion and make sure the ignition wire connections are tight.

This also could be an open loop condition, when the engine is intentionally run rich (think choke). Do you smell a strong smell of fuel at the exhaust when this occurs, maybe you have a leaky injector, that clears out. You could have your oil tested to see if you have fuel in it. We have a company that will analyze your oil.

Drive the car a bit and see if any codes come back, next time don't erase them, its important to see any codes including history

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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I am having the same problem with my 96. I have the same code also. That is the only useless code. I have a thread on it also. It usually clears up within a minute and runs great

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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This could be morning dampness on the ignition wires. When were your ignition wires last changed? Also, try cleaning the coil towers of any corrosion and make sure the ignition wire connections are tight.

This also could be an open loop condition, when the engine is intentionally run rich (think choke). Do you smell a strong smell of fuel at the exhaust when this occurs, maybe you have a leaky injector, that clears out. You could have your oil tested to see if you have fuel in it. We have a company that will analyze your oil.

Drive the car a bit and see if any codes come back, next time don't erase them, its important to see any codes including history

I think the wires are still original. Same with plugs. You might be right there. Will change all these within the next month or so. I will also have the oil tested, thats a good idea. Had it tested on my 87 HT4100 Deville, and all came back good. No real strong smell.

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I am having the same problem with my 96. I have the same code also. That is the only useless code. I have a thread on it also. It usually clears up within a minute and runs great

Might just be nothing then. Car also runs great. I wonder why Cadillac never pushed the viceral effects of the Northstar like the sound. The new Cadillacs does not sound nearly as nice.

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This could be morning dampness on the ignition wires. When were your ignition wires last changed? Also, try cleaning the coil towers of any corrosion and make sure the ignition wire connections are tight.

This also could be an open loop condition, when the engine is intentionally run rich (think choke). Do you smell a strong smell of fuel at the exhaust when this occurs, maybe you have a leaky injector, that clears out. You could have your oil tested to see if you have fuel in it. We have a company that will analyze your oil.

Drive the car a bit and see if any codes come back, next time don't erase them, its important to see any codes including history

I think the wires are still original. Same with plugs. You might be right there. Will change all these within the next month or so. I will also have the oil tested, thats a good idea. Had it tested on my 87 HT4100 Deville, and all came back good. No real strong smell.

Ok go to this site we have used them for oil analysis >> http://www.blackstone-labs.com/

I would say fuel pressure regulator but that typically only affects HOT start, not cold start. Something tells me that if you have old ignition parts that is where you should begin. You can also check for a leaky injector by lifting the fuel rail and supporting it with a block of wood and turning the key to ON, NOT RUN, to pressurize the rail and see if you have any leaks at the injectors.

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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I would think leaking injectors would have the same symptoms as a leaking fuel pressure regulator.

I'm thinking something ignition related - this is probably a good candidate for a Tech 2 to monitor the misfire counds when the car acts up - that would pinpoint it to a specific cylinder (and ignition component).

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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  • 2 weeks later...

Replaced the plugs yesterday. They had already been done, but with 41-947 and 0.05 gap

I replaced them with 41-950 and 0.06 gap as specified under the hood. Might be just my imagination, but seems a bit smoother.

What is the difference between those two plugs? Car seems to run a bit cooler now. Even cooler than before, but yesterday wasn’t very warm, so could be something else. 26.3 mpg at 70 mph. 193 degree or so. I wonder why Cadillac never spoke of the visceral effect of the Northstar when it revs up. Really is a lovely sounding engine.

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I just looked at a crossover chart and the 947 and 950 crossover to a different NKG plug, as such, these two plugs do not appear to be alike.

See this chart, its a little dated but it may be informational,

http://www.acdelco.com.au/PDFs/Catalogue_ACDelco_Spark%20Plugs.pdf

Personally, I would use the gap that is on the hood, a few years ago we had a heated discussion over the proper gap.

Rockauto shows the 41947 for $6.21 each next to the 41950 at $4.58 each odd... They have a close out on the 41947 and the 41947 is only for 97 and 98 according to rockauto. I was unable to find the difference between these two plugs, but they are both listed at Platinum.

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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  • 1 month later...

Found the problem. Fuel pump. The startup got progressively worse. Replaced the fuel pump, and all is good again. What a job though.

Glad you got the problem fixed.... :hatsoff:

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So thats how the fuel pump fails. In the beginning, engine has maybe a bit of shudder at startup. Not bad, but noticible if you pay attention. After a few months I had to turn the key for a few seconds to get the car to start. Sometimes try twice or three times. Still had enough power on the road, but I guess if I did not replace the pump, it would have just died on me one day.

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