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I have a 2006 Buick LaCrosse 3.8L that is misfiring. There is a strong smell of gas when running.

I have had this issue before and it was solved by replacing the ignition control module. I also replaced the plugs, wires, and coil pack while I was at it.

This time, replacing the ICM twice had no effect. I also replaced the coil pack a second time. Still nothing. I have an inline spark tester and it lit up on every cylinder when put between the coil tower and plug wire.

I have a bluetooth ODB reader, a multimeter, and the aforementioned spark tester. I am getting code P0300.

Tests I have run:

  • Spark test with inline tester, all OK.
  • Spark test by looking for sparking at the coil towers, all OK.
  • Removed plug heat shields. No change.
  • Unplugged MAF. No change in engine running, maybe that's it? I didn't run it very long with the MAF unplugged though.
  • Checked battery. OK.

Tests to run:

  • Cylinder by cylinder injector check.
  • Compression test
  • Fuel rail valve test.
  • Smoke test
  • Check brake booster.
  • Check PCV valve.
  • Check vacuum line. I did see one going from the top of the engine to the intake and I didn't see anything obviously wrong with it.

I would also like to add that before this happened, I had issues with the car RPM fluctuating under heavy load. You could hear the RPM fluctuating and the car lurching.

I would also ask that you take a look at the spark plugs I got just in case they're the wrong ones.

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  • Do a compression test on all cylinders.
    – Moab
    Aug 10, 2020 at 17:58
  • Welcome to Motor Vehicle Maintenance & Repair! While I'm not suggesting you replace either one, I'm wondering if a cam position sensor or crank position sensor may be going bad. If you could pick up a used one from a junk yard, it might be worth your time and money to attempt replacement on the cheap ... I wouldn't just buy new ones, as I'm sure they aren't cheap. I don't know how you'd test either one of them, either. Looking at sources, they aren't too expensive new. I'm not a fan of Remove & Replace wrenching, so would consider this a "last step".
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Aug 10, 2020 at 17:59
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    @Moab I will get a compression tester soon and update my findings.
    – a person
    Aug 10, 2020 at 22:34
  • @Pᴀᴜʟsᴛᴇʀ2 Wouldn't that trigger a code? I saw an S10 with that code.
    – a person
    Aug 10, 2020 at 22:35
  • @aperson - It can if the error is bad enough. Usually it will just not allow the engine to start at all. Like I was saying, it's just something to test, but not something I'd do as a first test.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Aug 11, 2020 at 1:12

1 Answer 1

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The strong smell of gas suggests leaking, stuck, or very dirty fuel injectors. I see there is a Fuel Rail Pressure Relief Valve on your vehicle that may be worth checking. Replace the fuel filter if it is very old.

When you connected the spark tester, did the light flash perfectly evenly? Watch the flashes for a full two minutes to be sure. Remove spark plugs wherever they are accessible and check for dirty condition.

Air leaks in the induction system is another possibility. Look for cracked or disconnected vacuum hoses under the hood. Check especially the condition of the PCV valve and it's hose. Check the brake booster. Perform a smoke test for other leaks, such as the EGR valve and its regulator, and the throttle body.

Check the condition of the battery. Its voltage should read about 12.8 V when the car is off. If it reads 12.6 or below, replace the battery. When the cars on, voltage should read between 13.7 - 14.7 v.

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  • I will try these various tests as I am able and update the post with my findings as I complete them. What do you mean by the light flashing perfectly evenly?
    – a person
    Aug 10, 2020 at 22:38
  • youtube.com/watch?v=PnU-SY6egr4 Is this the smoke test you are referring to?
    – a person
    Aug 11, 2020 at 13:34

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