Tech Tips
GM TSB Regarding Bugged PROM




A copy of a General Motors TSB for
86 LB9
(Camaro IROC is the same)

PONTIAC ROUGH IDLE, CHUGGLE, LOW SPEED.
Page: 1
86-6(GAS)-66
Issued: 10/17/86

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1986 FIREBIRD VEHICLES WITH 5.0L LB9 TPI ENGINE (ENGINE CODE F)


New service calibrators (Ref: Called Mem-Cal In Shop Manual) have been released for the 1986 Firebirds with the 5.OL TPI engine. These new calibrators will address the following customer comments:

1. "
Rough Idle" on both hot and cold engine - the idle speed is raised to 650 plus or minus 50 RPM.

2. "
Chuggle or Shudder" at low speeds - torque converter clutch (TCC) engagement speed is raised to 41 MPH.

3. "
Hesitation" on light acceleration with a hot engine.

4. "
Cold Driveability" - New calibration eliminates light to moderate sag on cold driveaway.

5. "
Service Engine Soon Light - Eliminates the following false Codes:

A. Code 32 - EGR System failure
B. Code 33 - Mass Airflow Sensor Voltage High
C. Code 34 - Mass Airflow Sensor Voltage Low
D. Code 43 - Electronic Spark Control
E. Code 44 - Lean Exhaust Indication

If normal engine diagnostics and repair do not correct the above conditions, it will be necessary to replace the calibrator in the ECM.
Below is a listing of the new calibrators and their usages.

ON AIR CONDITIONING (C-6O) FIREBIRDS

With QYZ (P215/65 R 15/N 15" Tire) Use - 1228290 Calibrator
With QAC (P235/60 VR 15N Tire) Use - 1228291 Calibrator
With QDZ (P245/50 VR 16N Tire) Use - 1228291 Calibrator

ON NON-AIR CONDITIONING (C-41) FIREBIRDS

With QYZ (P215/65 R 15/N 15" Tire) Use - 1228292 Calibrator
With QAC (P235/60 VR 15N Tire) Use - 1228293 Calibrator
With QDZ (P245/50 VR 16N Tire) Use - 1228293 Calibrator

Use Applicable Labor Time and Operation Numbers.

For use in 1227165 ECM only.

1228291 Calibrator available $63.64 F.O.B. factory, April 1999

ECM/Cal-Pak (PROM) for Model Year / Engine

YR. ENGINE OPTIONS P/N PROM CODE(S)

86 5.0-F A/C, VD1,VE1 (Export) 16061103 1107BLL

86 5.0-F A/C, VB4, BT7 (Export) 16061117 1120BLN

86 5.0-F Fed, Calif, A/C, 215/65/15 tires 1228290 3234ANY / 8958AMU 8969ANB / 8980ANY / 8993AUM

86 5.0-F Fed, Calif, A/C, 235/60/15&16 tires 1228291 3236AUM / 8958AMU / 8969ANB / 8980ANY / 8993AUM

86 5.0-F Fed, Calif, Exc A/C, 215/65/15 tires 1228292 3240BTZ / 8964ANA / 8975AND / 8987BTZ / 8998AWC

86 5.0-F Fed, Calif, Exc A/C, 235/60/15&16 Tires 1228293 3243AWC / 8975AND / 8987BTZ / 8998AWC

86 5.0-F VD1, VE1 Exc A/C (Export) 16059564 9567BUR

86 5.0-F VB4, VT7 Exc A/C (Export) 16059576 9580BUT

86 5.0-F Fed, Calif, A/C, 3.42(GU6) 16059000 9004AWD

86 5.0-F Fed, Calif, Exc A/C, 3.42(GU6) 16059006 9009AWF

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This TSB brought to attention by 3rd Gen Member "Vader" Below is a personal note from him regarding his experience in this issue.

This item is from a Technical Service Bulletin, not a recall. Not all owners reported problems with their vehicle's performance, so there was no recall. However, just because problems were not reported, they still exist if the PROM has not been changed. If you remove the cover from the ECM, you can remove the PROM carrier. Inside the carrier are three ICs. One is a resistor network, one is an I/O buffer, and the large one if the PROM (memory chip). The PROM should have a label with a revision number, something like "DELCO AUM 6339". There should also be a set of numbers inked on the PROM. Four of these are the date code.
If the date code is not 8646 (1986, 46th week) or higher, your PROM has never been changed.

The replacement has been programmed to raise the idle, enrich the mixture at mid range, hold off the torque converter clutch lockup to 41 MPH from 28 MPH, allow for a wider range of MAF signals, MAT signals, allow for a lower coolant temperature before entering full closed-loop operation, allow for richer O2 readings, and much more. Basically, you will notice a real difference in how your car operates.

I had a Hypertech Thermo Chip in my TA when I found out about the new PROM, and the GM reprogramming is better than the Hypertech in my opinion. The replacement only cost $63.00 from the dealer, and they were still available as of April of 1999.


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