PROM - Check Engine, Surge, Hesitation, Code 34
86olds01SUBJECT CHECK ENGINE LIGHT (CODE 34), ENGINE NUMBER: 85-T-55
SURGE, ENGINE HESITATIONS
DATE: May 1, 1986
MODELS/YEARS 1985 FIRENZA MODELS WITH 2.8L MPFI
ENGINE (VIN CODE W) SECTION: 6E
Customer comments may be received on some 1985 Firenza models with the 2.8L MPFI engine regarding check engine light (Code 34), engine surge, or engine hesitation. Listed below is some information that should help to correct each condition.
Item No. 1 Check Engine Light (Code 34)
Code 34 will set if the following conditions are met:
^ Engine running
^ Mass Air Flow sensor (MAF) disconnected, faulty relay or MAF signal circuit shorted to ground
^ Air flow less than 2 grams per second (low frequency)
To correct a Code 34 check engine light, first make sure that the MAF relay is working and supplies + 12 volts to the MAF sensor. This can be accomplished by connecting a test light between ground and the "+" terminal of the MAF sensor harness. With the ignition "on", the test light should light. If the light doesn't light, check for an open in the + 12 volt supply or a faulty relay.
If power is supplied to the MAF sensor, use the standard fault tree for check engine light (Code 34) in Section 6E3 of the Service Manual.
Item No. 2 Engine Surge
Item No. 2A If the vehicle exhibits surge, follow procedures in Section B - Symptoms, Section 6E3 of the Service Manual for diagnosing surge. Particular attention should be given to:
^ Checking rear spark plug wires for heat damaged wires. Replace if damaged.
^ Checking spark plug wire boots for evidence of carbon tracking. If carbon tracking is present in spark plug boot replace both spark plug and spark plug wire.
Item No.. 2B If the surge does not go away, update of the following parts should correct the condition.
Figure 1:
^ Install the latest PROM unless the vehicle already has it. (This can be done by using Figure 1).
The latest PROM has revised EGR scheduling when the torque converter is locked. This should reduce surge.
Item No. 3 Engine Hesitation
If the engine exhibits hesitations during accelerations when the engine is cold, update the following parts to correct the problem.
Figure 1:
^ Install the latest PROM unless the vehicle already has it. (This can be done by using Figure 1).
^ If the vehicle has early production injectors, install the updated injectors which have a revised spray pattern. The updated injector is part of a kit part number 1711297, (six (6)) kits required per engine.
NOTICE: Injectors with the correct spray pattern have already been installed on engines with a build date code of 0107 (January 7th) or later.
Example: T 01 07 CAF
This code is stamped on the horizontal machined surface of the block just forward of the intake manifold.
If the engine continues to exhibit a hesitation after the above updates, follow diagnostic procedures for hesitation in Section B-Symptoms, Section 6E3 of the Service Manual.
NOTICE: One of the steps in the Service Manual is to perform the injector balance test. It is important to run this test because it will identify plugged injectors. If the injectors are plugged, clean the injectors using recommended service procedures.
LABOR OPERATION NUMBERS AND LABOR TIMES
Item No. 1 Check Engine Light (Code 34)
Labor Operation Number: T1148 -- Code 34 Diagnosis
Labor Time: .4 hours
Item No. 2 Engine Surge
Item No. 2A Labor Operation Number: T1149 -- Symptoms Diagnosis
Labor Time: ST (Straight Time)
NOTE: THIS IS A ST (STRAIGHT TIME) OPERATION WHICH REQUIRES TIME DOCUMENTATION. ZONE APPROVAL IS REQUIRED BEYOND .5 HOURS.
Item No. 2B Labor Operation Number: T1150 -- PROM
Labor Time: .3 hours
Item No. 3 Engine Hesitation
Labor Operation Number: T1151 -- PROM and/or Injector - R & R or replace.
Labor Time: 1.6 hours Add
With A/C .1 hours
Scope Test .3 hours
Compression Test .4 hours
Injector Harness Check
With J 34730-2 .2 hours
Injector Balance Test .3 hours
Clean Injectors .5 hours
Figure 1:
PROCEDURE TO IDENTIFY AND INSTALL LATEST PROM
If scan tool is available, determine PROM I.D. using a scan tool, find scan data in column A of Figure 1 and perform action in column C.
If scan tool is unavailable, remove ECM from vehicle and determine PROM I.D. by visually inspecting PROM. Find PROM code in column B of Figure 1 and perform action in column C.