Jump to content
CaddyInfo Cadillac Forum

Help with rough idle !


kigy311

Recommended Posts

Since the temperatures droped in NW Pennsylvania my 1998 Deville is running rough for about 1-2 minutes when I start the engine cold.After that everyting is OK.Any ideas what might cause it?No codes.Thanks. :(

Link to comment
Share on other sites


We have had a few members complain about rough idle when cold, the first suggestion is your FPR... maybe, when its cold its stiff, when did you change it last?

When did you change your oil last and what viscosity are you using? (just a thought), you might want to use 5W30, I am from Havertown, Pa originally and I know how cold it gets up there having been to Altoona and McKeesport a few times...Brrrrrr

Maybe someone could comment on how the cold might affect an open loop running condition, maybe your roughness goes away because the system goes into closed loop...

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

Link to comment
Share on other sites

There could be a fuel pressure regulator issue or a manifold air plumbing leak that closes after a little heat buildup. Best to identify it now since it will not be as easy to locate in warmer weather.

...

Maybe someone could comment on how the cold might affect an open loop running condition, maybe your roughness goes away because the system goes into closed loop...

Open loop fuel management will compensate for temperature (air density) to deliver the proper amount of fuel. Remember back to carburetors and chokes to appreciate just how good open loop operation really is.

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

Link to comment
Share on other sites

There could be a fuel pressure regulator issue or a manifold air plumbing leak that closes after a little heat buildup. Best to identify it now since it will not be as easy to locate in warmer weather.

...

Maybe someone could comment on how the cold might affect an open loop running condition, maybe your roughness goes away because the system goes into closed loop...

Open loop fuel management will compensate for temperature (air density) to deliver the proper amount of fuel. Remember back to carburetors and chokes to appreciate just how good open loop operation really is.

With that in mind assuming the FPR is good, what could be wrong in open loop that might cause a rough idle? A dirty TB or IAC?, air filter?, causing a rich condition?

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

Link to comment
Share on other sites

The system won't go into closed loop until the oxygen sensors start giving signals. With the ECT sensor and the IAT sensor, the PCM knows what to do. We don't hear this from Canadian Cadillac owners who park their cars outside at -40 F (-40 C). It's got to be a minor tuning problem that is brought out when the FI is running open loop with a very cold engine.

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.

Link to comment
Share on other sites

How old are your spark plugs? When I changed my spark plugs, a slightly rough idle when cold went away and all is smooth again.

Jason(2001 STS, White Diamond)

"When you turn your car on...does it return the favor?"

Link to comment
Share on other sites

Check the condition of your battery, mine would stutter and feel like it was missing when first started, once I jumped hard on the gas when moving it would be fine.Then one cold night the car wouldn't start, battery was dead. I replaced the battery and have not had the missing when started. I think the problem is the battery gets drained startng the engine and you don't have enough power to run all the electronics until the alternator can get it enough power to fire the ignition system properly. We all know what a power drain is put on a battery starting a engine in cold weather.

Link to comment
Share on other sites

I'm with Jason and Caddypete....

In cold weather, your battery has got to be good.... you do not want to get stranded and freeze to death.... and if you do, I would refer you to your local mental health professionals.

And an iffy plug can run fine in warm weather, but crap out when it gets cold, and you desperately need it....

There's definitely smarter guys on here than me, but my 2 cents, if I have rough running rough starting problems, step one is plugs and wires.... which usually solves it. Once you know that's good, you can go from there if you still have problems.

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...