Question about 2002 Chevrolet Impala

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Car wants to start but dies immediately. fuel pressure test bad

170k miles, 2002 chevy impala 3.8

car turns over fine and almost starts but cuts out. i can hold the gas pedal down and start it, and it will run at about 2500rpm but very very rough with white smoke.

replaced ignition module and coil packs, fuel pressure regulator
replaced fuel filter, it was dirty
rented fuel pressure test kit from auto store
1. when key was in on position, pressure jumped to 56psi. mfr specs are 53-60
2. as soon as fuel pump turned off, the psi dropped to 49 and held
3. we thought the fuel pressure regulator might be bad so we replaced it
4. now, with the new regulator and the old one too, the pressure jumps to 56 and diminishes to nothing. doesn't even hold at 49psi anymore.

do you think i have an injector stuck open?

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  • 7 more comments 
  • Nick Tenza Feb 18, 2009

    i'm in a cold climate but presently its only 50 degrees or so. we did smell antifreeze one time from a backfire in the engine area, but not from the exhaust at all.

    we checked and rechecked the fuel pressure with both the new and old pressure regulators several times, switching them in and out. when you turn the key to the on position, the fuel pump can be heard pressurizing for about 2 to 3 seconds which is normal, at which time the reading is 56psi. then when the fuel pump disengages the pressure gradually goes to zero over about 10 seconds.

  • Nick Tenza Feb 18, 2009

    also replaced cam and crank sensors

  • Nick Tenza Feb 19, 2009

    okay, oil level is a quart high. gas has apparently gotten into the oil from flooding the cylinders. next step is to pull the fuel rail and see if all the injectors are stuck open or what?

  • Nick Tenza Feb 20, 2009

    hmm wow well, pulled the rail and injectors, found a leak on the fuel return line that was unnoticeable while the rail was still in place. fixed that and pressure holds steady as it should.

    injectors perform as they should, fuel pressure holds, it was the fuel leak. perhaps the fuel in the oil is because we've tried to start it up so many times?

    put it back together with the fuel leak fixed and it does start and run for a while but is very very rough like the timing is way off but it doesn't backfire.

    perhaps the intake manifold has failed on this?
    we put on new, clean plugs and wires and it runs the same.


  • Bruce Bracey
    Bruce Bracey May 11, 2010

    Nick, Did the oil get changed? I assume it did. Run the engine for a short period of time and change the oil and filter again. Fuel contaminated oil takes a while to clear out.

    The crank case ventilation system (PCV) is introducing addition fuel vapor into the engines induction system which then confuses sensors into thinking the engine is running to rich and will tell the ECM to go lean on the fuel mix.

    Drive the car 25 miles and change the oil again to clean it out and then see if the engine begins to stabilize.

    Let me know.


  • Bruce Bracey
    Bruce Bracey May 11, 2010

    Nick, You are correct, pull the rail up and look for the leaking injector.

    If you are planning on keeping the vehicle for a long time, you might want to consider replacing all injectors. Or remove the rail and take it to your local GM dealer and they can flush the rail and injectors to clean them.

    And please don't forget to change the oil.

    Good luck.


  • Bruce Bracey
    Bruce Bracey May 11, 2010

    It is very possible you have a stuck injector, however, your description of white smoke concerns me. Are you located in a cold climate? If not are you may be burning anti-freeze. If you smell the white smoke and it smells "sweet" it is anti-freeze. If it is merely water vapor it will not have the sweet smell to it.

    Let me know.


  • Nick Tenza Nov 21, 2013

    Just wanted to give an update on this. Replacing the manifold absolute pressure sensor (MAP sensor) solved the problem. go figure.

  • Nick Tenza Nov 21, 2013

    Replacing the manifold absolute pressure sensor (MAP sensor) solved the problem.



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  • 49 Answers

Couple of things, the fuel pressure held before with the old regulator but now it doesn't. Are you sure you got the tiny o-ring out when you changed it and installed it on the new one? Is there any fuel in the vacuum line to the regulator? Does the white exhaust smell like fuel or coolant burning?

Posted on Mar 05, 2015


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SOURCE: 2001 Chevy Malibu, 89,000 miles, 3.1 engine, won't start

CLICK HERE for the injector schematic.
CLICK HERE for the Ignition schematic.

Since the PCM uses info gatheres from the crank and cam sensors to calculate ignition - and there are no OBD codes - in all likelihood, the PCM itself is bad.

The Ignition Module, also transmits to the PCM.

It appears after all your testing - that the PCM is at fault.

It does not error report on itself (unfortunately).

The ignition timing is controlled by the Powertrain Control Module (PCM). No adjustment is necessary (distributorless ignition) or possible.

Please see the following....

The ignition timing is controlled by the Powertrain Control Module (PCM). No adjustment is necessary or possible.
The engines covered by this manual are equipped with distributorless ignitions, ignition timing is controlled by the Powertrain Control Module (PCM), as applicable. No adjustments are possible. If ignition timing is not within specification, there is a fault in the engine control system. Diagnose and repair the problem as necessary.
Ignition timing is the measurement, in degrees of crankshaft rotation, of the point at which the spark plugs fire in each of the cylinders. It is measured in degrees before or after Top Dead Center (TDC) of the compression stroke.
Ideally, the air/fuel mixture in the cylinder will be ignited by the spark plug just as the piston passes TDC of the compression stroke. If this happens, the piston will be at the beginning of the power stroke just as the compressed and ignited air/fuel mixture forces the piston down and turns the crankshaft. Because it takes a fraction of a second for the spark plug to ignite the mixture in the cylinder, the spark plug must fire a little before the piston reaches TDC. Otherwise, the mixture will not be completely ignited as the piston passes TDC and the full power of the explosion will not be used by the engine.
The timing measurement is given in degrees of crankshaft rotation before the piston reaches TDC (BTDC). If the setting for the ignition timing is 10 BTDC, each spark plug must fire 10 degrees before each piston reaches TDC. This only holds true, however, when the engine is at idle speed. The combustion process must be complete by 23° ATDC to maintain proper engine performance, fuel mileage, and low emissions.
As the engine speed increases, the pistons go faster. The spark plugs have to ignite the fuel even sooner if it is to be completely ignited when the piston reaches TDC. Spark timing changes are accomplished electronically by the engine and ignition control computers.
If the ignition is set too far advanced (BTDC), the ignition and expansion of the fuel in the cylinder will occur too soon and tend to force the piston down while it is still traveling up. This causes pre ignition or -knocking and pinging-. If the ignition spark is set too far retarded, or after TDC (ATDC), the piston will have already started on its way down when the fuel is ignited. The piston will be forced down for only a portion of its travel, resulting in poor engine performance and lack of power.
Timing marks or scales can be found on the rim of the crankshaft pulley and the timing cover. The marks on the pulley correspond to the position of the piston in the No. 1 cylinder. A stroboscopic (dynamic) timing light is hooked onto the No. 1 cylinder spark plug wire (2.2L engine only, on the 2.4L engines, special adapters are needed) . Every time the spark plug fires, the timing light flashes. By aiming the light at the timing marks while the engine is running, the exact position of the piston within the cylinder can be easily read (the flash of light makes the mark on the pulley appear to be standing still). Proper timing is indicated when the mark and scale are in specified alignment.

WARNING When checking timing with the engine running, take care not to get the timing light wires tangled in the fan blades and/or drive belts.

The engines covered by this manual are equipped with distributorless ignitions, ignition timing is controlled by the Powertrain Control Module (PCM), as applicable. No adjustments are possible. If ignition timing is not within specification, there is a fault in the engine control system. Diagnose and repair the problem as necessary.

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Posted on Aug 18, 2009

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