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Tim's Auto Repair
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Experience:  Have owned a repair shop for 25 yrs.
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1991 Chevy lumina euro: under load..3000 rpm..changed plugs..misses

Resolved Question:

I have a 1991 Chevy lumina euro with a 3.1 and it is missing under load at around 3000 rpm. I've changed plugs and wires but it still misses.
Submitted: 7 years ago.
Category: Chevy
Expert:  Tim's Auto Repair replied 7 years ago.


does the engine light come on?if so,tell me the codes



Customer: replied 7 years ago.
NO engine light at all.
Expert:  Tim's Auto Repair replied 7 years ago.


you may have one of 2 possabilities...1 the coils you may have one breking down...2 the ignition module,most parts stores like auto zone can test these if you take it off and take it to the store


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Description and Operation


Ignition Coils" width="277" height="153"/> Ignition Coils
Ignition System Schematic

Three twin-tower ignition coils are individually mounted to the ignition control module. Each coil provides spark for two plugs simultaneously (waste spark distribution). Each coil is serviced separately.

Two terminals connect each coil pack to the module. The ignition coils share a fused ignition feed. The other terminal at each coil is individually connected to the module, which will energize one coil at a time by completing and interrupting the primary circuit ground path to each coil at the proper time.

Service and Repair


Ignition Coil And Module Installation
Firing Order Schematic



  1. Spark plug wires.
  2. 2 screws securing coil to ignition control module.
  3. Ignition coil.


  1. Ignition coil.
  2. 2 screws, torque to 4-5 Nm (40 lb. in.) .
  3. Spark plug wires.
Description and Operation


Electronic Ignition (EI) System With Ignition Control (IC)

The Ignition Control Module (ICM) performs several functions:


  • It powers the 3X crankshaft sensor circuit.
  • It determines the correct ignition coil firing sequence, based on 3X pulse. This coil sequencing occurs at Start-up. After the engine is running, the module determines the sequence, and continues triggering the ignition coils in proper sequence.
  • It sends a "3X crankshaft reference" (fuel control) signal to the PCM. The PCM determines engine RPM from this signal. It is also used by the Powertrain Control module (PCM) to determine crankshaft position for ignition control spark advance calculations. The signal sent to the PCM by the ICM is an "ON-OFF' pulse occurring 3 times per crankshaft revolution
Service and Repair


Ignition Coil And Module Installation
Ignition Coils



  1. A 6-way connector, 3-way connector and 2-way connector at ignition control module.
  2. Spark plug wires from ignition coils.
  3. 6 Screws securing ignition coils to ignition control module.
  4. Disconnect coils from ignition control module.
  5. Ignition control module.


  1. Ignition coils to ignition control module.
  2. 6 screws, torque to 4 - 5 Nm (40 lb. in.) .
  3. Plug wires.
  4. 6-way connector, 3-way connector and 2-way connector to module.
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