Skylark L4-138 2.3L DOHC VIN D MFI QUAD 4 (1989)
Fuel Injector: Customer Interest
Engine - Intermittent Miss or Loss of Power
Bulletin 90-6E-19
Date Nov. '90
Ref. No. 90-201-6E
Corp. Ref. No. 076502
SUBJECT:
INTERMITTENT ENGINE MISS OR LOSS OF POWER - REPLACE LOW RESISTANCE FUEL INJECTOR
MODELS AFFECTED: 1989-90 SKYLARK WITH 2.3L QUAD 4 ENGINE (VIN D)
A concern of intermittent engine miss on one cylinder or loss of power may be caused by an injector that has a decreased electrical resistance value.
On the 1989 and 1990 Quad 4 engine, the injectors are fired in pairs. The ECM transistors that control the firing of the injectors are current limiting.
That is to say, the current in the circuit can peak to 4 amps then is reduced to 1 amp. This feature is referred to as "peak and hold".
If the electrical resistance value of an injector decreases as little as 0.4 ohms, the injector will consume excess current from the ECM and leave less
current to drive the adjacent injector with the proper, electrical resistance value. The cylinder with the good injector stops operating while the cylinder
having the injector with decreased electrical resistance continues to operate. In other words, the injector in the "dead" cylinder is good and the injector in
the "live" cylinder is faulty.
The suggested diagnostic procedure is to make a list of the injectors driven by the same ECM terminal as the affected cylinder. Cylinders 1 and 4 are
paired and so are cylinders 2 and 3. Measure the resistance of those injectors. Substitute the injector having the lowest electrical resistance with a
"known good" part. Then re-evaluate the driveability concern.
