Help!!! with rough idle - 98 cadillac seville
 

i was wondering if i could get a few suggestions on my 98 cadillac seville, at startup it idles rough for a few minutes or until revved up, the rpms fluctuate between 700-850, it runs great when driving, very responsive but as soon as i come to a stop i can feel it missing, its starting to bother me ALOT! i have done a few things to it, but do not want to throw anymore new parts at it for it to not be fixed, so i'll ask the pros, so far this is what i've done.

i cleaned the egr valve, and replaced the gasket

changed air filter

plugs and wires

i am thinking ignition coils or pcv valve, maybe clean the throttle body as a next step, but would be appreciative of any info to help me along my way!!!! so if any techs are out there and you see this Heeeeeeeeeeeeeeelp ! [:-]

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RE: Help!!! with rough idle
 

I don't know how long you've been troubleshooting cars, so I'll dare to mention the IAC (Idle Air Control) valve to you. [/align]http://autorepair.about.com/cs/gener.../bldef_333.htm

I had to replace this on my '98 Ford van at about 70,000 miles. I bought one at either Pep Boys or Autozone, so a visit to the dealer is not necessary.

This gadget is commonplace to modern engines, where idle mixture screws used to suffice in the old days of carburetors. IACs will degrade, and cannot be repaired. When your IAC goes, your car will die at stop signs. It is a feature of fuel-injected engines, and allows for bypass at low idle to the engine won't suffocate and shut off.

Help!!! with rough idle - 98 cadillac seville
 

the parts you have changed will do little to the problem you described.
you must have CODES .. we need the CODES.
please read: https://www.cadillacforum.com/m_9792/tm.htm

coils show failure much more under load, not idle.


the two major and common issues:

- build up of coke in the throttle body - use SeaFoam - I believe there is a write up in the FAQ
- ISC motor (idle speed motor) has failed or gone out of adjustment .. (some call it IAC)

in some cars, the ISC is adjustable, in some it is not.
I dont have your model manual to check.

RE: Help!!! with rough idle - 98 cadillac seville
 

thanks! i am going to use seafoam today, can i put it through the pcv valve hose? or is there a better recommended vacuum line than that? i also will try putting ISC in. will let you know how it goes!

RE: Help!!! with rough idle - 98 cadillac seville
 

Putting through the PCV works but you also need to clean the butterflies at the throttle intake with it.
Its sold in spray can or in pint cans. I am cheap .. I use the pint can, load it into a spray bottle.
more stuff for your buck. This stuff will not only clean the throttle intake, but a great deal of the intake
manifold and even the intake valves.
BUT *** BE READY FOR A LOT OF SMOKE *** .. when you do it, engine running of course, the amount
of smoke Seafoam produces, is unbelievable.

I am NOT recommending that you go and buy a ISC until you do that. Even then, you should test
the one you got, these things aint cheap.

oh, also check the connector the the ISC .. it only works if connected properly.
you be surprised how many cars get the air intake tube pulled for whatever, disconnect it,
damage it, etc ...

RE: Help!!! with rough idle - 98 cadillac seville
 

do i remove the air intake and assembly and spray into the screen?

RE: Help!!! with rough idle - 98 cadillac seville
 

figured out how to clean throttle body, cleaned it drove about 20 miles and now service light is on, i reset it 3 times throughout the drive, but kept coming back on, im getting 3 codes now and was wondering if these were normal or if i should be concerned the codes are

IPM B1343
PCM P1111
PCM P0113

anyone have any answers for this??

RE: Help!!! with rough idle - 98 cadillac seville
 

disregard last post, it was the sensor that plugs into air intake, just got in a hurry and forgot to plug it in and about the 1343 i kno it involves my heat i dont know how to fix it though any help with that would be awesome! was also wondering how i can get the shake out of my front end, it shakes when braking at speeds 45+, brakes fine from 45 and under i replaced front brake and rotors rotated tires and was recently aligned...wondering if tires off balance could do that or if its struts, ball joints, or tierods? or all the above! anyone have any ideas?

RE: Help!!! with rough idle - 98 cadillac seville
 

UPDATE- after last week I had had it with the car and was at Auto zone getting more dex-cool and was looking at the head gasket repair items. I know what you are thinking- that stuff does not work. I have been told by many people that you cant fix a blown head gasket with a bottle. I agree but dont know what I was thinking and bought it anyway because it said double your money back guarantee so I thought there was nothing to loose. It was a product from called K&W nanotechnology permanent head gasket and block repair in a green bottle. I hope this does not sound like a comercial or anything but it worked!
The car has not even past the normal since. All I had to do is flush the system of all coolant add the bottle to the upper hose, top off with water and run the car for 20 min. drain overnight, flush system. refill system and now everything is cool.
I dont know how long it will work for but its running good for now.