http://www.caddyinfo.com/idlelearn.htm

You can't begin to tell me that's the procedure the Goodwrench guys use to re-learn the Idle speed values.

I just finished cleaning my TB and when I put it back in, startup revs to about 2500 then comes down, and while driving, if I get above 30kph, the engine will idle at 1025 RPM until I come to a COMPLETE stop. Then it goes back down to 575-650.

ISC was replaced a year ago...EGR was replaced at the same time TB was cleaned...ideas?

Yup, that is it. My 91 Book doesnt have the 13min idle line, but all the rest it does. Key is to make sure it is up to temp, and in diagnostics it is in closed loop, and coolant temp is 92 C or so (give or take a couple).

Step 4-14 are triggers to tell the ECM that "hey, this bozo wants you to learn now" steps. Then the actual learning is steps 14-18. 18 telling it to save.

Now, key thing is to ensure that the throttle bores are clean, I mean CLEAN at the points of min idle air. Any disruption of airflow will cause the ECM to increase throttle angle and that will be more uncontrolled air through (as you open the blades it will give more air than it wants, so it becomes hard to manage accurately).

Cadillac designed the idle air with great precision :worship: , so precise that dirt isn't allowed. It will flub up the idling :mad: . I cleaned mine with a rag (don't EVER run an engine with a rag near the throttle opening :banghead: !!!!) and learned mine, and it made a difference at 25 mph and slower, But I need to clean it up more, I bought some X66S at the dealer (Top Cyl Cleaner), hope there isn't any coatings on the blades, because it will likely eat it off :eek: .... But that stuff will clean that area very very well :coolgleam , and also decarbon the tops of the pistons and the chambers if you follow the proceedure properly.

Personally I would have use a IAC solenoid, but it adds costs, and of all things Cadillac designed that were $$ on the 4.9L, this is one area they skimped on.

Tom

If you cleaned the throttle body then you can forget the idle learn procedure. It just isn't needed. Just disconnect the negative battery terminal for 60 seconds to reset the idle learn offsets to the default value....which is for a clean throttle body. The engine is idling fast with the clean throttle body because the idle learn offsets were very high due to the deposit buildup that was blocking air flow around the perimeter of the blades. Now that they are clean the idle learn offsets need to be reset to the "clean throttle body" values by disconnecting the battery. That is all that is required.

BTW...did you clean the EGR tubes while you were in there...??? Those are the two tubes sticking up from the floor of the intake below the throttle blades. They are supposed to be clean and not full of carbon. Rod them out with a piece of stiff wire.

bbobynski, I have surfed around and found that you have a lot of info and know abouts on Caddys. I have been smackin my head aginst the wall :banghead: trying to figure out why my 99 sts idles so rough every time you start it after sitting for at least 30 min. I cleaned the TB like your one post said, then changed the plugs, fuel filter, but it still starts rough and feels like it is missing until it warms up just alittle. I have not figured out how to access the computer control, I have an OFF button but not the warmer, they are on the same dial, so i can't get the computer to tell me anything. I know its more OE :hmm: do you have any ideas that it might be? if feels though it's misfiring, :bonkers: but when it gets going it's just fine. Thanks for any info that you might have or be able to help with this.

BTW...did you clean the EGR tubes while you were in there...??? Those are the two tubes sticking up from the floor of the intake below the throttle blades. They are supposed to be clean and not full of carbon. Rod them out with a piece of stiff wire.

Stiff wire didn't to jack all...the carbon in those tubes is a greasy, thick paste, which will require liberal amounts of TB cleaner and a bottle brush.

Where exactly do those tubes lead? When I was shoving the wire down there I hit bottom, how do I know that when I scrape all of that carbon off the tubes that it isnt just going to rest at the bottom plugging up something else?

trying to figure out why my 99 sts idles so rough every time you start it after sitting for at least 30 min. I

I would ohm out the wires and coils. Ensure they are all good. Sounds like a bad coil, bad plug or bad plug wire to me. Seen it a few times on my 91 Bonneville, which has the same basic ignition system. Lack of ignition voltage will idle rough when cold started. But run ok when warm. But it will deteriorate and run poor hot also. Bucking at WOT is also sometimes seen.

Never thought out NOT needing to learn it with clean bores! Good call! Defaults are nice to have set properly!

Tom

Stiff wire didn't to jack all...the carbon in those tubes is a greasy, thick paste, which will require liberal amounts of TB cleaner and a bottle brush.

Where exactly do those tubes lead? When I was shoving the wire down there I hit bottom, how do I know that when I scrape all of that carbon off the tubes that it isnt just going to rest at the bottom plugging up something else?

My 85 Cutlass 307 was so plugged what I thought was bottom was actually carbon build up!! Took a drill bit to fix even after I removed the tubes (they were threaded).

Try using GM's X66P or X66S to clean them, it is carbon remover. It is awesome :worship: stuff. See your local GM dealer, old timers know it as X66, else it is called "Top Engine Cleaner" now, P is pour, S is aerosol spray. Get the spray.

Get some long Q-Tips from RadioShack, and soak it in the cleaner and then you can feel around for the bottom to be opened up. Flashlight might show too.

The tubes just lead to a passage that goes to the EGR valve. You can take off the EGR valve (use a new gasket when replacing!!! Exhaust leaks under the hood suck!) and run a piano wire through or you can blow it out too. Again, use googles.

Tom

The tubes just lead to a passage that goes to the EGR valve. You can take off the EGR valve and put yourself through hell and back again. Dont forget to write! :devil:
Tom

NOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO I needed to remove the TB just to get at the EGR bolts...and I just replaced it!!! Bah.

The EGR gasket is reuseable as long as it doesn't stick and tear when you remove the valve.

Take the throttle body off and use a drill bit to clean out the passages. The tubes lead to a passage below that leads to the EGR valve as described. The carbon that falls down below will usually just blow thru the engine with no problem so it really isn't much of a worry. If you use the drill bit most of it will end up at the top of the tube and fall into the manifold so you can use a shop vac to clean it up.

Rough idle....hard to say. May be a weak spark plug or wire. Check the continuity of each wire and the resistence of each wire with a VOM. Check from the metal terminal inside the boot on the plug to the terminal inside the cap boot. Check for missing terminals...sometimes they get pulled off when a boot is removed. If a plug is ever fouled it will recover and run fine when hot but will often cause a misfire when cold. The fouled plug leaks spark down the porcelean which is etched with a small fissure. This cleans up when the plug warms up but will cause cold misfire when the remaining fissure collects liquid fuel during a cold start. It may need another set of plugs if the wires are bad and causing one cylinder to misfire.

Don't you have a button that you push to make the climate control go to a "WARMER" setting...??? Simultaneously press and hold that button and the OFF button with the key on to interrogate the onboard diagnostics.

Interestingly enough...im getting P070 which is Intermittant TPS Signal

Well, thats 1 thing to try

Call me crazy but im honestly starting to think that my ISC is out of adjustment seeing as how it was calebrated for the TB when it was crapped full of carbon...perhaps I should readjust?