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Ron
Ron, ASE Certified Technician
Category: Car
Satisfied Customers: 10
Experience:  10 years working on cars and light trucks. I work with all aspects of vehicle repair and diagnostics
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93 Eldorado: stall..pcm to icm, and Replaced ignition coil pack

Resolved Question:

After my 93 Eldorado runs for a while it will stall. I can instantly restart it, but I must keep my foot on the gas to keep it running. I have had the following done at different times in this order: Repaired shorted wiring in ISC wiring harness & set engine to specs, and performed idle learning procedure, Replaced CPM and MAP, Replaced ignition module, Diagnosed code P023 and rewired wiring harness wiring for circuits 423 and 424, and from PCM to ICM, and Replaced ignition coil pack.
Submitted: 6 years ago.
Category: Car
Expert:  Ron replied 6 years ago.

Hi,

My name is XXXXX XXXXX I will be glad to help you.

The Idle Learn Procedure is different from the Throttle Position Sensor Learn Procedure of the PCM (Power Control Module).


Throttle Position Learn
A Throttle Sensor Learn procedure has been implemented in the PCM software to allow the PCM to correct or offset the closed throttle signal value of the TP sensor. This is necessary because of manufacturing tolerances during minimum air adjustment, TP sensor manufacture and because the TP sensor is not adjustable on the throttle body. If an improper TP sensor offset is maintained by the PCM, a closed throttle engine sail-on or stall condition may occur. Performing the Throttle Position Sensor Learn procedure lets the PCM learn the correct Throttle Position Sensor offset.

Idle learn
An IDLE LEARN Procedure has been implemented in the PCM software to allow for a loss of air flow through the throttle body during closed throttle operation. This reduction in air flow can be caused by deposit buildup on the throttle valve.

OPERATION
The IDLE LEARN procedure is different from the Throttle Position Sensor procedure of the PCM. TP SENSOR LEARN is performed by the PCM after the ignition is turned to "OFF". IDLE LEARN is performed by the PCM when the engine is running and specific conditions are met.

The IDLE LEARN routine of the PCM calculates a throttle angle correction or offset that is used during closed throttle idle control. If an improper throttle angle offset is maintained by the PCM, a closed throttle engine sail-on or stall condition may occur. Performing the IDLE LEARN procedure lets the PCM learn the correct throttle angle offset.

WHEN TO PERFORM TP SENSOR IDLE LEARN PROCEDURE
The TP SENSOR/IDLE LEARN procedure should be performed when:

  • The TP sensor is replaced.
  • The ISC motor is adjusted or replaced.
  • The throttle body is replaced.
  • The PCM is replaced.
  • The PCM EEPROM is replaced.
  • If TP SENSOR/IDLE LEARN is reset using PCM override PS 13.

TP SENSOR/IDLE LEARN PROCEDURE

  1. Outside air temperature is at least 10°C (50°F) so that the A/C compressor will turn "ON".
  2. Start the engine.
  3. Allow the vehicle to idle continuously until the coolant temperature is 80°C, then idle an additional 5 minutes.
  4. At end of 5 minutes, enter diagnostics (engine still running).
  5. Turn ignition to "OFF".
  6. Wait a minimum of 20 seconds.
  7. Turn ignition to "ON" (engine not running).
  8. Enter diagnostics.
  9. Turn ignition to "OFF".
  10. Wait a minimum of 20 seconds.
  11. Turn ignition to "ON" (engine not running).
  12. Enter diagnostics.
  13. Turn ignition to "OFF",
  14. Wait a minimum of 20 seconds.
  15. Start the engine.
  16. Apply the brakes and place the transaxle in "DRIVE" range.
  17. Turn the Climate Control Center (CCC) to "OFF" and allow the engine to idle for 30 seconds.
  18. Turn the CCC to "AUTO", verify A/C compressor engageent occurs. Allow the engine to idle for another 30 seconds.
  19. Place the transaxle in "PARK" range and turn ignition to "OFF".

DIAGNOSTIC NOTES

NOTE: Make sure nothing is touching or obstructing the accelerator or brake pedals during the TP SENSOR/IDLE LEARN procedure because this will prevent the PCM from performing the learn procedure.

NOTE: High electrical loads may disable TP SENSOR/IDLE LEARN. Components that may produce a high electrical load are the headlamps, the rear defogger, high HVAC blower and the cooling fans. If difficulty is encountered learning TP SENSOR/IDLE LEARN values (i.e. Code P080 remains current), turn "OFF" these high electrical loads. Also, it is important to accelerate the engine above 1000 RPM after turning "OFF" the above components because the PCM will think it is still under a high electrical load until it checks the system again (when engine rpm exceeds 1000 RPM). Furthermore, since the cooling fans can not be manually controlled, engine coolant temperature must be below 105°C and A/C refrigerant temperature must be below 510°C.

Well this is alot of information but it should answer what you have already done and if it was done correctly and/or if you have more to complete before your vehicle is happy again.

Hope this answers your question and gives you the tools to fix your issue. If you need anything else I will be happy to help.

Thank you, Ron

Customer: replied 6 years ago.
Ron, your answer was not clear, Seems to me that you are suggesting doing a procedure-Ilde Learn-that was done. All of the work noted in my question was done at a Cadillac deakler by an ASE certified technician. But he was 0 for 4, and his last suggestion-replace the full body and engine wiring harness-was to me overkill. Besides, I could not afford for him to go 0 for 5. That's what sent me to you. You stated doing a throttle position sensor learn procedure but noted that the PCM calculated a throttle angle offset during an Idle Learn procedure. What should I have done and what's your opinion on replacing the full body and engine wiring harness?... ThanksCustomer
Expert:  Ron replied 6 years ago.

Hi,

This is Ron. Sorry that I was not clear. I will clarify myself to you towards the end of this message but first to offer my opinion on your wiring harnesses.

My opinion to replacing your body and engine harness may not be to far fetched if there are signs of chewing or nesting of varmets in the engine compartment etc... which happen.

Example: I have had to repair a harness then replace the PCM on a Chevy Truck due to rats nesting in the engine compartment and chewing on wires in a couple of locations. Luckily they only chewed through the wire insulation and not cut the wire because re-splicing wires with butt connectors, adding wire, etc... is not a proper repair as it changes the amount of resistance between a sensor and the PCM and can cause miss readings and therefore cause Driveablility issues. Also routing sensor wires etc. near spark plug wires/high energy circuits can cause sensor miss reading issues. Keep this in mind to wiring repairs that you have stated you had repaired. This information I have learned through training with the purchase of my shops High End Scanner (Modis) and I have extensive knowledge of electronics (my first luv).

I hope I can clarify myself? In your question you stated that a Idle Learn Procedure was done and I was showing that their is also a Throttle Position Sensor Learn Procedure that is different. If all Learn procedures were completed and you still have a stall problem then I would like to know if it was like that when you picked it up from the shop after the repairs were completed or how long afterwards? If it was doing this stalling when you picked it up from the shop then I would as a customer ask them what is going on (why is my car stalling?). If it happened after awhile from the last repair then I would suspect a sensor may have failed or a connector may have came loose/disconnected. Please let me know a little more detail of when this particular problem accured and if it has been the same from the first repair to the last repair and why were wiring repairs needed?

If this helps great and if you can give me more information I can help you further and better. If I have given you all the information you need to answer your question then please accept. Keep in mind I am here to help you so please do not hesitate to contact me.

Thank you, Ron

Customer: replied 6 years ago.
Ron, there were time intervals between repairs, but all repairs were for the same problem-when the temp reached about 200 the car was likely to stall at a stop or if I took my foot off the gas. On restart the engine would surge contineously or would surge for a period and then stall. There were intervals when the car ran without a hitch. Here are the REPAIRS and DATES: (1) 8/18/06 odometer 150780 Repaired shorted wiring in ISC wiring harness & set engine to specs, and performed idle learning procedure, (2) 3/13/07 odometer 152621 Replaced faulty CPM and replaced shorted MAP,(3) 4/17/07 odometer 152737 Replaced ignition module, (4) 9/24/07 odometer 154414 Car stalled but technician was unable to duplicate,(5) 10/02/07 odometer 154606 Diagnosed code P023 and rewired wiring harness wiring for circuits 423 and 424, and from PCM to ICM, (6) 10/9/07 odometer 154763 Replaced ignition coil pack, and (7) 10/18/07 odometer 154947 Technician stated he was unable to perform any more repairs... noting that the engine and body wiring harness was very brittle. Service Rep said that the wiring harness must be replaced, but noted that it would be costly and that I should consider selling the car. While the car was not driven a lot during this period it was frequently started and moved...otherwise it would have been towed by the police. I hope this helps.. ThanksCustomer
Expert:  Ron replied 6 years ago.

Hi, Thank you for giving me this information. It is a great help and expains a lot.

Your vehicle is 15 years old and if a service advisor and/or technician is saying your wiring harness is dried out and cracking then I would say you will continue to have problems with this vehicle until you can replace the harness. Unfortunately patching the harness little at a time will be costly in the long run as it would be just to have it replaced now plus as I described in my last advice that patching wires change there resistance values and lead to other problems. Yes it is expensive to have this done and with the information you provided me it does make sense to rid of the car or have the harness replaced if you feel the car is worth that to you. I have had numerous customers in my shop fix there vehicles and know what is done rather than buy a used car and end up with something they hope they get lucky with and have no problems. It would be impossible to diagnose a specific problem when the wiring harness is failing and causing issues. The problem with your wiring, if it is really dried and cracking, will eventually cause sensors to fail and the PCM (Vehicle Computer).

I hope I helped you with your problem even if it means bad news. I hate giving bad news but I give honest answers.

Thank you, Ron

and please if you need more help I will be glad to help.

Ron, ASE Certified Technician
Category: Car
Satisfied Customers: 10
Experience: 10 years working on cars and light trucks. I work with all aspects of vehicle repair and diagnostics
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Ron
Ron
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10 years working on cars and light trucks. I work with all aspects of vehicle repair and diagnostics