SURGE -CHUGGLE 52-60 MPH. NEW SERVICE PROMS

Models Affected: 1985 Fleetwood Brougham (RWD), Eldorado and Seville (Federal and Altitude Emissions), Eldorado Biarritz Convertible (National and Altitude Emissions)

The following driveability condition may be noted in some 1985 Fleetwood Broughams, Eldorados, and Sevilles equipped with an HT4100 engine and Federal (NA5), Altitude (NB2) or National (Eldorado Biarritz Convertible) emissions controls:

1. Some vehicles may exhibit a 52-60 MPH surge or chuggle under moderate acceleration with the Torque Converter Clutch engaged (MAP parameter .0.2 at about 85-90 kPa).

Before installing the revised calibration PROM to improve a chuggle or detonation complaint, the following checks must be performed to verify proper basic engine and/or fuel control operation.

1. Perform the DFI System Check Chart in Section 6D4, subsection A of the 1985 Seville, Eldorado and Rear Wheel Drive Brougham Service Information Manual. Diagnose and repair any trouble codes found as well as any fuel system rich or lean indications that may be discovered using the "Field Service Mode Check: portion of the DFI System Check Chart.

2. Use the symptoms diagnosis in section 6D4, subsection B of the 1985 Seville, Eldorado and Rear Wheel Drive Brougham Service Information Manual. The symptom diagnosis chart that should be used is "Surges and/or Chuggle.

The revised PROM will not repair a chuggle or detonation condition that is the result of a basic engine or fuel system condition. Installation of the PROM into a car with an engine or fuel system condition will not repair a surge or chuggle --- a customer comeback will be the likely result.

Customers may notice that the TCC does not apply as frequently with the revised PROM calibration as with the original production PROM. In addition to changing fuel, spark and EGR calibration, the new calibration changes the criteria used to apply TCC as follows:

Original Calibration New Calibration -------------------- ---------------

1. Vehicle speed greater than 48 MPH: 53 MPH; 2. TPS reading from 6 to 23 degrees; 8 to 16 degrees; 3. Delay before TCC is applied is 5 secs. 15 secs.

In summary, a vehicle equipped with the new calibration must be driven above the minimum speed and within the throttle angle limits specified for at least 15 seconds before the TCC will apply.

PROM part numbers for 1985 Longitudinal HT4100 cars (exclusing California emissions) are as follows:

Retrofit (revised)PROM Regular Service Replacement Use for Surge Use for regular PROM Replacemenbt, Code 51,etc. Broadcast Broadcast Service No. PROM I.D. Code Service No. PROM I.D. Code ---------- -------- ---- ----------- --------- ---- "D" FED 1227381* 103 HYA 16056001 102 HYA "D" ALT 1227386 * 128 HYH 16056103 127 HYH

"E""K"FED/MECH 1227382** 137 DKD 1227382 137 DKD "E""K"FED/DIG 1227383** 167 DKF 1227383 167 DKF

"E"NAT CONV/MECH 1227384** 138 DKM 1227384 139 DKM "E"NAT CONV/DIG 1227385** 168 DKN 1227385 168 DKN

"E""K"ALT MECH 1227387** 159 DKK 1227387 159 DKK "E"ALT CONV MECH 1227387** 159 DKK 1227387 159 DKK "E""K" ALT DIG 1227388** 189 DKL 1227388 189 DKL "E"ALT CONV DIG 1227388** 189 DKL 1227388 189 DKL

NOTES:

FED = Federal Emissions Calibration (NA5) ALT = Altitude Emissions Calibration (NB2) NAT = National (Fed/Cal)Emissions (Convertible) MECH = Mechnical Instrument Cluster (UY9) DIG = Digital Instrument Cluster (U02) D = Fleetwood Brougham E = Eldorado K = Seville CONV = Eldorado convertible

* The retrofit (revised) PROMs for Fleetwood Brougham DO NOT supersede the regular replacement service PROMs. The retrofit PROMs for the Fleetwood brougham are to be used only as required to resolve cases of chuggle.

** The Retrofit (revised) PROMs for all Eldorado and Sevilles supersede all previous Service PROM part numbers. The Retrofit PROMs are to be used as both the regular service replacement, (PROM damaged or defective), and to resolve cases of chuggle.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.