idle relearn?

[trace]

i have a 1990 deville...it started having problems a couple months ago....with hesitation...so over that period of time, we have had a tune-up done, replaced the catalyst converter...taken apart the injectors and cleaned them...when that didnt resolve the problem, the dealer put an additive into the gas tank called 44k....great stuff...took care of the problem...but then a new one started....

the idle is high...and when coming to a stop, it comes down hard making the car jump...it is sucking up gas at an amazing rate too...the dealer we had it at said that he tried adjusting the idle down, but the computer kept compensating, and it would go right back up...they said they just didnt have anyone knowledgeable about caddies that old..so we took it to another dealer, who said they did an idle relearn...couldnt get rid of the problem, but seemed to slow it down...thats their opinion...i disagree...it was the same and getting worse

we replaced the idle control actuator...and the connector harness attached to it...and for the first few minutes of driving it after that, it was normal...then it was right back doing the same thing...

so we tried to reset the computer...followed the steps in the manual...the final step says to put the climate control set to "auto"....which when we got to that part, i realized...we cant do that, cuz my climate control wont go into "auto" cuz it stopped working last summer...i was told that i have the old a/c and that it would cost hundreds of dollars to recharge it, that i should have it converted...which i havent yet done...because of this other problem...

so...here is my question(s)....is it possible that the reason i cant get the idle to relearn is because of the problem with the climate control system? how do i know if i need to just convert the system, or if i need to replace the computer? is it at all possible that just converting it will solve the problem? is there a way to bypass it? what else could be causing this problem?

oh yeah...forgot to mention...there are no recent codes...

i am absolutely going crazy here...ive been to 3 cadillac dealers, and 2 repair shops...and no one seems to be able to figure it out...suggestions appreciated!

[Sweede64]

Air leek, check the gasket below the throttlebody, quite common on GM TBI. Try some ether and spray it on the seem betweene the intake and TB, if idle changes you foun the fault.

[TJ Hopland]

Bad fuel pressure regulator?    I think the 90's had multi port injection.   If I recall correctly the regulator is between the ends of the fuel rail.  If you are standing in front of the car its the right end of the fuel rail and its closer to the front bank.  Its visible with everything still installed.  It has a connection to the fuel rail and then the return fuel line back to the tank.   If you follow the 2 fuel lines they will lead you to it.  One line goes direct to the rail the other goes through the regulator.  The regulator also has a vacuum line attached to it.   I think its a short piece with a bend in it.   If you pull that hose off and there are any signs of gas you found your problem.   Part is about $70 and its not too bad to replace.   Fuel rail has to come off to get to it so sometimes some other things have to be removed to make room.  On my 95 I think the power steering and alternator had to come off.   



The reason it could affect the idle is the diaphragm has ruptured and is allowing fuel to get sucked direct into the intake instead of going through the injectors and such.  The computer senses the extra fuel so it adds air to keep the balance correct.  Also since the regulator is not working there is more fuel pressure than there is supposed to be so each injector pulse delivers more fuel per shot so it tends to run on the rich side all the time which is why your mileage is terrible.    If the regulator is leaking it will also make it hard to start because there is no fuel pressure in the fuel rail and the intake is flooded.   

[Dave Shepherd]

I would go into self diagnsotics and look at the coolant temp sensor readings, if it stays on the cold side when the engine is warmed up the idle will not come down and you will use more gas.

[Art Woody]

TJ and Dave may be on to something. I would try Dave's suggestion as it is an easy fix and about a $10 cure if it remedies your problem. I had similar problem with my '89 RS Camaro. The coolant temp sensor reported a sub zero reading to the computer which in turn richened up the injectors causing the idle to run wild. After going on the same merry-go-round as you are, a country bumpkin mechanic (a lovingly referred to nephew) at the local BP station, suggested this remedy. I had a complete spare full system on my workbench that I played musical idle sensor, injector, and everything but colant temp sensor, right under my nose. This was not the sensor that reads your water temp for my instrument gauge. Good luck I hope it helps.

[tracey]

  If the regulator is leaking it will also make it hard to start because there is no fuel pressure in the fuel rail and the intake is flooded.   

would there be a raw gas odor? there isnt any problem starting.

[tracey]

I would go into self diagnsotics and look at the coolant temp sensor readings, if it stays on the cold side when the engine is warmed up the idle will not come down and you will use more gas.

how do i go into self diagnostics? i did recently have my radiator replaced, the old one was leaking...the car doesnt have a problem warming up...heat works real good.

[TJ Hopland]

would there be a raw gas odor? there isnt any problem starting.

There would be gas or gas odor if you pull off the vacuum line to the regulator but usually not if everything is connected.  Usually cold starts are hard so that may not be your problem.  Its easy enough to check just pull the vacuum line off (or have your mechanic do it) for a look and sniff.  I dont think there were any clamps. If its leaking the hose gets mushey so its really easy to pull off.  Its easy to eliminate so you can focus on other possible issues.

On earlier models the diagnostics were something like  off-defrost-warn on the climate control panel.   Its been too long so my memory is not so good. Its also handy to have the book because after it reads off any trouble codes there is a test procedure that requires you do do certain things at the proper times like step on the brake and gas pedal with the engine running and not running.

[TJ Hopland]

How did we ever survive without the net?  No wonder I cant remember anything, I dont have to, its all out there somewhere.

Its OFF and WARMER you hold down to enter the mode.

http://myweb.accessus.net/~090/cadidiag.html

There is an index that covers most years of Cadillac's since they got computers.

[Dave Shepherd]

how do i go into self diagnostics? i did recently have my radiator replaced, the old one was leaking...the car doesnt have a problem warming up...heat works real good.

Go to caddyinfo.com, the entire procedure and codes are listed. The coolant temp sensor has nothing to do with the engine's temp, only the input to the pcm.

[CEC #20099]

CEC #20099
90 Cad - The OBD 1 diagnostics are basically very stupid. Don`t count on finding a useable current or history code.
The car will relearn during a series of drive cycles, without the Climate Control relearn.
One thing not to ignore is the throttle position sensor, bolted to the rear of the throttle body. They do wear out, are a bitch to replace, due to stupid design,
and need to be calibrated with a voltmeter. The factory shop manual is invaluable here.
Fuel regulator can easily be checked with a pressure gauge.

Sounds like you need a good "Wrench" , not a dealer, if you are not familiar with these systems.
C. Chleboun

[Art Woody]

If your coolant temp sensor is reading a temp colder than it actually is, your idle will be stepped up (via a false message sent to the computer) as if starting a cold engine and stay there even after engine is at normal maximum running temp. A common failure on this era GM product.

[Wayne Womble 12210]

Also need to perform a minimum idle adjustment.   This basically takes the IAC out of the equation and sets the baseline idle.  The computer adjusts from that point.  This will tell you if you have a vacuum leak, which is most likely from the symptoms.