SURGE - NEW SERVICE PROMS FOR CALIFORNIA VEHICLES

MODELS AFFECTED: 1985 FLEETWOOD BROUGHAM (RWD), ELDORADO, AND SEVILLE (CALIFORNIA EMISSIONS)

The following driveability conditions may be noted in some 1985 Fleetwood Broughams, Eldorados, and Sevilles equipped with an HT4100 engine and California emissions controls (NA6):

1. Some vehicles may exhibit a 42-50 MPH surge or chuggle under moderate acceleration with the Torque Converter Clutch engaged.

2. Some vehicles may exhibit a tip-in or "burst" detonation (spark knock), which may be noticed during rapid throttle angle changes, such as a wide open throttle acceleration away from a stop. The tip-in detonation may be more prevalent at hot ambient temperatures and/or with use of regular octane gasolines.

3. Some vehicles may exhibit a "flatness" sensation if a light throttle acceleration manuever is performed with TCC engaged.

BEFORE installing the revised calibration to improve a chuggle or detonation condition, the following checks must be performed to verify proper basic engine and/or fuel control system 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 symptoms diagnosis charts that should be used are "SURGES AND/OR CHUGGLE", DETONATION/SPARK KNOCK", and "LACK OF POWER, SLUGGISH OR SPONGY".

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

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

Original Calibration Revised Calibration --------------------- ------------------- Vehicle Speed greater than 43 MPH 53 MPH TPS reading from 6 to 23 degrees; 8 to 19 degrees; Delay before TCC isapplied is 5 Secs. 15 Secs.

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

ROM part numbers for 1985 Longitudinal HT4100 cars with California emissions are as follows:

Retrofit (Revised) PROM Regular Service Replacement Use for Surge, Flatness Use For Regular PROM or Tip in Detonation Replacement, Code 51, etc. --------------------- --------------------------- Service PROM Broadcast Service PROM Broadcast P/N I.D. Code P/N I.D. Code

"D" CAL 1227629 * 110 DKA 16043757 28 DKA "E""K"CAL/MECH 1227389 * * 142 DKH 1227389 142 DKH "K"CAL/DIG 1227390 * * 171 DKJ 1227390 171 DKJ NOTES:

D = Fleetwood Brougham F = Eldorado K = Seville CAL = California Emissions Calibration (NA6) MECH = Mechanical instrument Cluster (UY9) DIG = Digital Instrument Cluster (UO2)

The Retrofit (revised) PROMs for the California Fleetwood Brougham DO NOT supersede the regular replacement service PROMs. The retrofit PROM for the Fleetwood Brougham is to be used ONLY as required to resolve cases of chuggle, detonation or flatness.

The Retrofit (revised) PROM for all California Eldorados and Sevilles supersede all previous Service PROM part numbers. The Retrofit PROM is to be used as both the regular service replacement, (PROM damaged or defective), and to resolve cases of chuggle, detonation, or flatness.

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.