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Tim's Auto Repair
Tim's Auto Repair, mechanic
Category: Chevy
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Experience:  Have owned a repair shop for 25 yrs.
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2002 chevy malibu: fuel pump..crank fuel pressure..psi

Resolved Question:

I am working on a 2002 chevy malibu with a 3.1, I am having problems with the car suddenly starting to chug and miss. The car was just tuned up, I just did the fuel pump and just replaced the crank sensor. I have checked my fuel pressure and I have 48 psi at an idle. the book says it should be at 52 to 59. I don't believe it is the fuel pressure regulator as when you throttle up the pressure jumps up to 60psi. It also fouled out #1 plug last week. I am using a genysis scanner and I can watch the engine misfire at an idle on all of the cylinders. Could this be the cam sensor or am I missing something?
Submitted: 7 years ago.
Category: Chevy
Expert:  Tim's Auto Repair replied 7 years ago.
do you get any codes?
Customer: replied 7 years ago.
None at all.
Expert:  Tim's Auto Repair replied 7 years ago.


the fuel presure is a little low,sense it does rise when you throttle,this problem would be the regulator,also,sometimes the diaphram will bust in these regulators,letting raw fuel go through the vacuum line,so docheck this...but i think your problem may be the ignition module,these will do this and not throw a is located under the coils auto zone and most parts stores can test these if you take it off and take it to them


please ACCEPT my answer so I can get credit for my work.i don't receive commission unless you do ..i'm not always going to be giving you good news,so please dont let this stand in the way of you accepting my does not cost you more money.we will still be able to communicate.. Bonuses and positive feedback are appreciated!if you are not satisfied with my answer,please do not leave bad feed back,i will gladly opt out and let another expert handle the question.PLEASE ASK IF YOU NEED MORE HELP

Engine NOT running 52 -59 psi at 0 rpm
Note: Check pressure with the key ON and the engine NOT running.

Testing and Inspection


Fuel System Diagnosis
The fuel pump fuse provides system voltage to the fuel pump relay. The Powertrain Control Module (PCM) grounds the fuel pump relay control circuit to energize the fuel pump relay. When the ignition is turned ON, the PCM commands the fuel pump relay ON for at least 2 Seconds , voltage is applied to the electric fuel pump and will continue to energizes the fuel pump after the PCM receives 3X reference pulses. The fuel pump is an electric pump and is part of the modular fuel sender assembly. The fuel pump supplies fuel through an in-line fuel filter, fuel rail assembly to the fuel injectors. A fuel pressure regulator, attached to the fuel rail assembly, maintains a regulated fuel pressure for correct operation of the fuel injectors. Any unused fuel is then returned to the fuel tank by a separate fuel return pipe.

Service and Repair




  1. Relieve the fuel system pressure.
  2. Disconnect the fuel pressure regulator vacuum line.
  3. Remove the fuel pressure regulator retaining screw.
  4. Use a shop towel in order to catch any spilled fuel, lift and twist the fuel pressure regulator in order to remove the fuel pressure regulator from the fuel rail.
  5. Remove and discard the retainer and spacer bracket from the rail.
  6. Remove the fuel pressure regulator from the engine fuel return pipe.
  7. Remove and discard the inlet O-ring from the fuel pressure regulator.


CAUTION: Connect the fuel return line before tightening the regulator attaching screw in order to prevent the regulator from rotating. Rotation of the regulator could damage the retainer and spacer bracket and lead to a fuel leak at the regulator inlet.


  • Do not use compressed air in order to test or clean a fuel pressure regulator as damage to the fuel pressure regulator may result.
  • Clean the fuel pressure regulator filter screen with gasoline if necessary.
  • Do not immerse the fuel pressure regulator in a solvent bath in order to prevent damage to the fuel pressure regulator.
  1. Inspect the filter screen for contamination. If the screen is contaminated, replace the fuel pressure regulator.
  2. Lubricate the new pressure regulator inlet O-ring with clean engine oil and install the O-ring on the regulator inlet.
  3. Install the fuel return pipe to the regulator.
  4. Install the new retainer and spacer bracket into the slot on the fuel rail. NOTE: Refer to Fastener Notice in Service Precautions.
  5. Install the pressure regulator to the fuel rail. Tighten Tighten the nut to 17 N.m (13 lb ft) .
  6. Reconnect the fuel pressure regulator vacuum line.
  7. Install the pressure regulator attaching screw. Tighten Tighten the screw to 8.5 N.m (76 lb in) .
  8. Inspect and verify that retainer and spacer bracket are engaged in the slots in the fuel rail. Grasp and pull on the regulator to ensure the regulator is properly seated.
  9. Install the fuel filler cap.
  10. Inspect for fuel leaks using the following procedure:
10.1.Turn ON the ignition, for 2 seconds .
10.2.Turn OFF the ignition, for 10 seconds .
10.3.Turn ON the ignition.
10.4.Inspect for fuel leaks.
Ignition Control (IC) Module


The Ignition Control (IC) module performs the following functions:


  • It determines the correct ignition coil firing sequence, based on 7X pulses. 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 the 3X crankshaft reference (fuel control) signal to the PCM. The PCM determines engine RPM from this signal. This signal is also used by the PCM to determine crankshaft speed for Ignition Control (IC) spark advance calculations.

The 3X reference signal sent to the PCM by the IC module is an on, off pulse occurring 3 times per crankshaft revolution.

Service and Repair




  1. Turn OFF the ignition.
  2. Disconnect all the electrical connectors at the ignition control module.
  3. Note position of spark plug wires for installation and disconnect the spark plug wires from ignition coils.
  4. Remove the screws securing coil assemblies to ignition control module.
  5. Disconnect the coils from ignition control module.
  6. Remove the fasteners securing ignition control module assembly to engine.
  7. Remove the ignition control module from the bracket.


  1. Install the ignition control module on the bracket.
  2. Install the coils to ignition control module.
  3. Reinstall the fasteners securing ignition control module assembly to engine. NOTE: Refer to Fastener Notice in Service Precautions.
  4. Reinstall the screws. Tighten Tighten the screws to 4-5 N.m (40 lb in) .
  5. Connect the spark plug wires as noted during removal.
  6. Connect the electrical connectors to the ignition control module.
Tim's Auto Repair and 3 other Chevy Specialists are ready to help you
Customer: replied 7 years ago.

Thanks I appreciate the help I will try the ICM!


Expert:  Tim's Auto Repair replied 7 years ago.


also pull the vacuum line off the regulator and see if fuel has been going through it

thanks for useing justanswer

Customer: replied 7 years ago.

The Icm did not work. Do you think the cam position sensor is bad?

Thanks, Jon

Expert:  Tim's Auto Repair replied 7 years ago.

it is posable..but i dont wont to have you throwing parts at it


7X Crankshaft Position (CKP) Sensor


7X Crank Shaft Position (CKP) Sensor
The 7X crankshaft position sensor provides a signal used by the ignition control module.

The ignition control module also uses the 7X crankshaft position sensor to generate 3X reference pulses which the PCM uses to calculate RPM and crankshaft position.

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