I've read a lot of threads on this forum and wonder what is the correct idle learn procedure on a Caddy 4.9 L engine. I've adjusted the TPS and the IAC's values to curb my sail on or engine push ,which was quite bothersome, but I'm not quite sure how to relearn my ECM to the new values. Does anyone know the correct way or sequence for the idle learn procedure? I even took the throttle body off for a thorough cleaning. Any experienced info would be greatly appreciated.
I've read a lot of threads on this forum and wonder what is the correct idle learn procedure on a Caddy 4.9 L engine. I've adjusted the TPS and the IAC's values to curb my sail on or engine push ,which was quite bothersome, but I'm not quite sure how to relearn my ECM to the new values. Does anyone know the correct way or sequence for the idle learn procedure? I even took the throttle body off for a thorough cleaning. Any experienced info would be greatly appreciated.
just let it idle for 5 minutes and then take it for a drive.. there's no rocket science to it.
Stickpony is correct. The book says Key on for 30 seconds off for 30 seconds the on again and start the engine and let it warm to operating temperature. The easiest way is to take the car for a nice drive with a couple of stops (shutdown) and you should be good.
Joe Sokol
------------------ 85 SE Daily driver with a 3.4 DOHC OBD II 88 Formula/GT 4.9 Allante Intake (My Baby)
I thought you had to disconnect the battery cable for 30 seconds, someone had that on one of the threads here.
It does. The TPS learn is done automatically everytime the key is turned off. The idle learn needs the battery disconnected before it will start learning.
Idle in park, drive, and with the AC on if you have it. The PCM needs to see any extra load on the engine while learning so it can compensate later on down the road.
quote
Originally posted by Fieroking:
Stickpony is correct. The book says Key on for 30 seconds off for 30 seconds the on again and start the engine and let it warm to operating temperature. The easiest way is to take the car for a nice drive with a couple of stops (shutdown) and you should be good.
Joe Sokol
This is the TPS learn. It differs from the idle learn. Warm the car to full operating temp. Shut off then cycle the key twice waiting until the ISC stops moving both times (This performs the TPS learn twice to be sure its accurate). Then you disconnect the battery for 20-30 seconds. Reconnect and let idle in park, drive, and with AC on if equipped.
To help eliminate the mystery from this procedure I will be doing a video how-to on the 4.9 idle learn procedure. I should have my car back together and ready to post by the end of next week.
[This message has been edited by Fieroseverywhere (edited 03-22-2010).]
Thanks Fieroseverywhere, I hope you will have your video soon. I 'm sure it will help all 4.9 L Fiero owners. Just a sidebar, I am having a devil of a time finding the idle stop screw on the throttle body. What size torx does it take and can it be adjusted without removing the IAC?
This is the idle learn procedure as taught by Rockcrawl....
Make sure the throttle plates and bores are clean before you start. Also make sure you don't have any vacuum leaks. Jumper ALDL A and B to enter the set timing mode. Verify timing at 10* BTDC and remove jumper. a).Disable the alternator by grounding the small brown wire, there should be a green connector inline if it's anything like a Cadillac harness. Disconnect the ISC motor where the main harness attaches to the sub harness. Attach two jumper wires to the blue wires of the sub harness. Connect one jumper to ground and the other to bat positive momentarily until the ISC is fully retracted. If it extends, reverse the polarity to make it retract. When it is fully retracted, the throttle lever should be resting on the minimum idle screw. If the throttle lever is touching the ISC plunger at full retraction, use a pliers to turn the plunger in until it's not touching. b).Use the minimum idle screw (recessed torx) to set the idle to 525 rpm. With the throttle lever resting on the minimum idle screw, set the TPS to .50 volts. c).Now you can extend the ISC by reversing the polarity of the jumpers. At full ISC extension, the TPS should read between 1.15 and 1.20 volts. Adjust the ISC plunger in or out with a pliers to obtain the correct TPS voltage. Retract the ISC. Reconnect the ISC to the main harness. Turn the key off and wait 20 seconds to allow the ECM to perform a TPS learn. d).Cycle the ignition on and off once more. It takes two cycles for a sucessful TPS learn. Perform and idle learn. Run engine until coolant temp is greater than 176*. Allow engine to idle in park for ten minutes. With brake applied, allow engine to idle in drive for at least three minutes. The ECM will command a 600 rpm idle. If it's not idling at 600 +/- 50 rpm after doing this procedure there is something wrong.
This is the service bulliton from Caddy that states to set the idle lower vetween 400 and 450 rpm,
Group Ref.: Engine
Bulletin No.: 316006A
Date: November, 1993
SUBJECT: SLOW DECELERATION WITH CLOSED THROTTLE ABOVE 5 MPH (READJUST AIR RATE)
MODELS: 1990-93 CADILLAC DEVILLES, ELDORADOS, FLEETWOODS, SEVILLES, AND SIXTY SPECIALS (EQUIPPED WITH 4.5L OR 4.9L ENGINES)
THIS BULLETIN IS BEING REVISED TO CORRECT THE WARRANTY STATEMENT, AND CANCELS AND SUPERSEDES BULLETIN 316006 PUBLISHED OCTOBER, 1993.
Some owners may comment about slow deceleration with closed throttle above 5 mph. This may be particularly noticeable after performing bulletin T-93-44 (Corporate bulletin 016540R) even though all engine adjustments have been set according to published service information.
To correct this condition readjust the minimum air rate to between 400 and 450 rpm, the TP Sensor setting to .55 volts, and reset TP Sensor/idle learns using the procedures listed in the appropriate Service Information Manual.
Thanks Fieroseverywhere, I hope you will have your video soon. I 'm sure it will help all 4.9 L Fiero owners. Just a sidebar, I am having a devil of a time finding the idle stop screw on the throttle body. What size torx does it take and can it be adjusted without removing the IAC?
Look at the screws that mount the ISC to the throttle body. Right between them you find a hole in the bracket. Inside that hole is the Minimum idle screw. T20 torx I believe. It can be adjusted with the ISC still in place but you need a tool to reach it.
Thanks Fieroseverywhere, Did the procedure as you sent and the car has no more sail on or engine push. It is more safe to drive and stop. Thanks so much. Really apppreciate.
Thanks Fieroseverywhere, Did the procedure as you sent and the car has no more sail on or engine push. It is more safe to drive and stop. Thanks so much. Really apppreciate.
You got lucky...I've been trying to do the idle learn for years and it hasn't worked yet. I finally had to unplug the ISC because it refused to calibrate properly.
Thanks Fieroseverywhere, Did the procedure as you sent and the car has no more sail on or engine push. It is more safe to drive and stop. Thanks so much. Really apppreciate.
Happy to help. For those who are interested here is a copy of the email I sent out. Maybe it will be of some help to others also...
quote
Originally emailed by Fieroseverywere:
First off start the car and warm to full operating temp. Double check timing and look for any vacuume leaks.
Next you get 2 jumper wires and remove the connector for the ISC. One jumper wire connects to +12v the other to ground. With the other ends of these jumpers touch the blue wires in the ISC connector (ISC side not PCM side). This should retract the ISC fully (if not reverse polarity). With the ISC fully retracted you can now adjust the minimum idle screw. Set it low, as low as you can with the engine still running. Even if its running badly its OK. Hopefully you can get to 400-500rpm. Now you can shut the car off but leave the key on. This setting will control how fast the idle comes down.
Once the min idle is set you can adjust the TPS. With the ISC still retracted loosen the screws and set the TPS to .55v. A scanner or multimeter will tell you the voltage.
The next step is to set the ISC screw to the correct range. While still reading the TPS voltage extend the ISC fully. With it fully extended check the TPS voltage. You are looking to be in the range of 1.15-1.2V (the lower the better). If your out of that range turn the ISC screw until you are. Let the throttle slam shut a couple times to make sure the settings stay.
Now reconnect your ISC and turn off the key. Wait 20-30 seconds for the PCM to perform a "TPS learn" (you'll hear the ISC moving while this is going on). Cycle the key on then back off again to do it a second time. Once done disconnect the negative battery cable for 20-30 seconds. Once reconnected its time for the "idle learn". Start the car and let idle in park, drive, and with the AC on (if equipped) for about 2 minutes in each. Go for a drive and enjoy. The car should no longer push and should stop much faster.
Hope this is some help.
[This message has been edited by Fieroseverywhere (edited 03-25-2010).]
I wanted to add one more thing that I recently found to be very useful. After 2 minutes of idling while PCM is learning, flip on ALL accessories, headlights, radio, heater, AC, and anything else that takes power. With any luck the cooling fan with come on also. Doing all this further increases load on the engine. It results in the PCM being able to compensate for changing conditions a little better. It will eliminate the sudden drop in RPM when the cooling fan, AC, or headlights come on.
I am planning on doing this IAC motor setting, and the TPS calibration sometime in the next few days. Waiting for a decent day weather wise.
Fieroseverywhere we never did get to see the video you were gonna make for all us newbies at this.
if your car is running fine as is, there is no need to do the calibration, you can measure where your calibration is at right now just by readouts on the scanner.. when you are slowing down coming to a stop, and your foot is off the gas and on the brake, if the tps is within the correct range of 1.0-1.2 v, , then you are fine, calibration is good.. check the low end by retracting the isc motor and checking the tps readout with the throttle plate closed, it should be around .45-.55 volts
i would not change the idle air screw on this engine. it is set from the factory and doesn't get messed with generally speaking. just my opinion.
unless you are having driveability issues, i wouldn't mess with it. the whole point of the idle learn procedure is to account for the small variances that occur between the ISC plunger position, the tps's position, and then adjust for them electronically in the computer.
[This message has been edited by stickpony (edited 01-12-2011).]
if your car is running fine as is, there is no need to do the calibration, you can measure where your calibration is at right now just by readouts on the scanner.. when you are slowing down coming to a stop, and your foot is off the gas and on the brake, if the tps is within the correct range of 1.0-1.2 v, , then you are fine, calibration is good.. check the low end by retracting the isc motor and checking the tps readout with the throttle plate closed, it should be around .45-.55 volts
i would not change the idle air screw on this engine. it is set from the factory and doesn't get messed with generally speaking. just my opinion.
unless you are having driveability issues, i wouldn't mess with it. the whole point of the idle learn procedure is to account for the small variances that occur between the ISC plunger position, the tps's position, and then adjust for them electronically in the computer.
My car is idling around 1200-1300 rpm. I want to set it down a bit. I will look at my scanner next drive sometime tomorrow. Thanks for the suggestions. -Joe
[This message has been edited by josef644 (edited 01-12-2011).]
My car is idling around 1200-1300 rpm. I want to set it down a bit. I will look at my scanner next drive sometime tomorrow. Thanks for the suggestions. -Joe
Thats not right. It should idle around 650rpm for an auto. Does it ever drop below that?
That is pretty well it. I am gonna do teh retract thing tomorrow and see what gives
Ok. The reason I asked was to determine if its the ISC holding it up or something else. If it was the ISC it may dip below from time to time. Didn't you have to do something with the throttle cable bracket once?
There is plenty of slack in the throtttle cable. I am not gonna remove the slack until I get the idle down. I have seen it drop as low as 850 a few times.
What is the heck have you guys used to reach that minimum idle speed screw? I can't even see the danged thing.
[This message has been edited by josef644 (edited 01-12-2011).]
My car is idling around 1200-1300 rpm. I want to set it down a bit. I will look at my scanner next drive sometime tomorrow. Thanks for the suggestions. -Joe
and thats your idle after the car is fully warmed up and in closed loop, according to the scanner? dont trust the readout from the tachometer, as it could be off. also, dont confuse "desired idle" with actual engine idle when you use your scanner. "desired idle" is not the actual idle speed.
your chip was programmed to idle at 600 when fully warmed up in closed loop. i tested it myself to make sure it was set properly
ignore the idle speed screw that is embedded in the throttlebody, you dont need to adjust it. if your idle was fine before you started having all the electrical problems, chances are the calibration wont be necessary... but if it always idled around 1200-1300, then you should do it.
a high idle can also mena a bad vacuum leak.. so keep that in mind
[This message has been edited by stickpony (edited 01-12-2011).]
Investigation time tomorrow, maybe Friday as the weather is supposed to get up to around 50*F again. Yesterday I had a hard time getting to 190 as the temperature was only 38 or less the whole day
Aaron at what temperature is the fan set to come on ?
-Joe
Forgot to add I am using the scanner for RPM. , not desired idle, or the dash tach.
600 RPM in which gear Aaron?
[This message has been edited by josef644 (edited 01-12-2011).]
There is plenty of slack in the throtttle cable. I am not gonna remove the slack until I get the idle down. I have seen it drop as low as 850 a few times.
What is the heck have you guys used to reach that minimum idle speed screw? I can't even see the danged thing.
The factory tool looks like this... I just grabbed a $2 T20 torx driver, and bent it. Works great.
[This message has been edited by Fieroseverywhere (edited 01-12-2011).]
Investigation time tomorrow, maybe Friday as the weather is supposed to get up to around 50*F again. Yesterday I had a hard time getting to 190 as the temperature was only 38 or less the whole day
Aaron at what temperature is the fan set to come on ?
-Joe
Forgot to add I am using the scanner for RPM. , not desired idle, or the dash tach.
Reviving an old post in hopes of finding a solution.
Can anyone tell me what the idle learn procedure is for a 1993 4.6L N* not using the dash controls? Doing the procedure above has some issues. The absolute lowest I can get the idle with the ISC off is 450~620 before the throttle plates bottom out in the bore. The idle is bouncing at this point. The TPS reads 0.41 volts but there is no way to adjust it to 0.5v without modification of the mounting holes as its a nonadjustable part on the N*.
The motor is a transplant into a hotrod so I have no dash controls to the access diagnostic mode used in the service manual. I'm using a scan tool that gives me the information I require.
The old ISC was damaged so I replaced it, now I can't seem to get a proper idle learn or I'm not doing something right. With the ISC installed the car revs really high at start and idles down to 850~900RPM in open loop, at 160F it going into closed loop and idles around 1025RPM. Commanded RPM in the bin is 650 for operating temperature. Also, when I give the throttle a bump and it idles down it does a momentary sail on around 1200RPM and slowly idles down. Would not be good driving this way. The car is not moveable at the moment as I'm doing suspension work.
I removed the ISC motor and the engine idles very low (450~600 bouncing idle), I could set it higher with the idle adjustment screw but without the ISC, quick releasing of the pedal from revving it up the motor has a bit of a hiccup due to the quick loss of incoming air into the intake before leveling out again.
