COLD STARTABILITY IGNITION DIAGNOSIS
MODELS AFFECTED: 1983-1984 CIMARRONS EQUIPPED WITH 2.0L ENGINE (VIN CODE P), AUTOMATIC TRANSMISSION, AND FEDERAL EMISSIONS SYSTEMS
Service Information Manual procedures for diagnosing ignition and EST system faults, including Code 42, cannot be used for vehicles updated per the cold startability special policy adjustment, 84-P-1 reissue. Vehicles that have had the cold startability adjustment will never set a Code 42, even when an EST or ignition system fault is present. Fault conditions in the EST system can cause symptoms such as spark knock, low power, cranks but will not start, hard start or poor fuel economy with no "Check Engine" light and no codes set. The following diagnosis and EST circuit schematic are for vehicies which have been equipped with the cold startability adjustment.
Condition Diagnosis (Refer to Figure 1)
1. Engine cranks but will not run 1. Disconnect "set timing" connector. or engine starts but immediately Attempt to start car.If engine starts, stops. check for an open or short to ground in CKT 423 between the ECM and distributor.
2. Hard start at -10 DEG F 2. Check for: (-23 DEG C) ambient or less. - Open CKT 906 between cranking motor May hear metallic "knock" and spark bypass relay. during crank. - Open spark bypass relay ground. - Faulty relay (not closing during crank) - On 1993 vehicies with VIN before 418443, check for the presence of an EGR valve vacuum bleed connector (P/N 14079541). Refer to Bulletin No. 84-7, Section 6C. 3. Spark knocks under heavy loads, 3. Check and note timing. Disconnectt loss of performance and fuel "set timing" connector and again note economy. timing. If there is no change in timing readings: - Check for open or short to ground in bypass CKT 424 between the ECM, spark bypass relay, and distributor. - Check for relay contacts sticking closed after crank.
In addition to these EST system checks, it is important that the ignition secondary is performing correctly. Check for open or shorted ignition wires, craced spark plugs, and other malfunctioning ignition parts.
Be sure that the correct spark plugs (R42CTS, P/N 5614009) have been installed in the vehicle, per the Special Policy Bulletin 84-P-1 reissue. If the above procedures do not repair the condition, the cold start kit and EST system are not the cause of the complaint and normal diagnostic procedures should be used to repair the ignition system.
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.
