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My 2003 Pontiac Grand Am GT will spudder and the engine will shake occasionally on cold starts. Its not a consistent problem - not every time, but it seems to be growing worse.

I can feel the engine shaking the car, then after a little bit of driving it will just automagically go away. I've been told it could be spark plugs, the computer, etc. I would love to do the repair myself, but I just don't know what to even dive into without knowing that I'll waste hours.

As well, when I'm accelerating (a lot), there's some kind of whistling noise coming from the front end of the car.

Any ideas, oh great gurus of fast moving stuff?

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Is there any check-engine light/code? This would be helpful in diagnosing the problem. –  R.. Apr 3 '13 at 4:33
    
While it is knocking, the light flashes. But it goes away once the engine returns to normal. As far as the code, I wouldn't know how to get it. –  Christopher Apr 3 '13 at 4:38
    
Get a cheap OBD-II scanner and plug it in. I've found auto parts stores have overpriced ones ($50-150) but this one on Amazon is cheap and does everything you need: amazon.com/Autel-MaxiScan-MS300-Diagnostic-Vehicles/dp/… –  R.. Apr 3 '13 at 4:40
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Also, some auto parts stores will do the scan for you without you buying anything (presumably because then they have a chance to sell you the parts to fix your problem), so that's a good option too. I just bought one when I needed it though because it was only $20 and I figured it would come in handy. –  R.. Apr 3 '13 at 4:42
    
Thanks! Is there anything else you can tell me in the meantime? –  Christopher Apr 3 '13 at 4:56
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4 Answers 4

Definitely sounds like the spark plugs or ignition coil to me. My father owns a mechanic shop in Boston and when my car was doing the SAME exact thing in the winter, he just replaced a certain spark plug and ignition coil that went bad and everything was all better.

You won't know for sure without checking. If you know what burned out spark plugs will look like, then you can find out which one it is and just change them out.

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First, make sure the spark plug wires are tight. On those cars it's easy to accidently knock one loose (loose enough to be intermittent) while doing an oil change.

Those cars also seem to eat ignition coils, so that's a likely candidate.

Spark plugs are also possible. Not very likely, but they're pretty cheap, so are often done first just in case they're the problem.

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Whistling noise aside ( one problem at a time ), spark plugs are cheap and easy to replace yourself. Try replacing your spark plugs and see if that solves at least one of your problems.

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First problem's first. A flashing check engine light means that something is wrong that could damage your engine. Others here are correct, it's probably a spark plug or coil pack issue triggering the light. A loose or fouled plug won't ignite the cylinder when cold, but when the engine has warmed up can have just enough spark to ignite and run the cylinder. If you have more than one doing this, then you could cause some damage. This can be cause by several things, but the easiest to check and replace are the spark plug wires and spark plugs. On the newer Grand AM & Prix cars, they use a solid state ignition and instead of a single coil, they use a coil pack. The coil packs usually don't go bad, but can.

Take it to someplace like Autozone that will read the codes from the car computer and print them out for you. The description they print out is usually pretty decent, but allow the person to go into a little more detail, but take it with a grain of salt until you verify it. I would expect to see a code similar to P0301, P0302, etc. The P30x codes are usually misfire codes and the last number should reflect which cylinder is misfiring. You may have several codes.

When you go to replace your spark plugs, make sure the engine is cool, and do one plug and one wire at a time. Pick one to start with, remove the spark plug wire, then the spark plug, double check your gap on the new plug, and carefully install the new spark plug. You don't want to over tighten it, but you don't want to have it took loose either. Solidly snug is an apt term. Although this may the time to buy a cheaper torque wrench and learn how to set it. The torque value should be specified in the manual. Then match the old spark plug wire up to a new one to find the correct length and install the new wire. Repeat for the other cylinders.

When you are all done, start the car and take notice if it behaves the same way and if the check engine light is still flashing.

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Brian Knoblauch is correct, a loose wire can be knocked loose easily, though 1 loose wire shouldn't cause a flashing Check Engine (CE) light. Check for 2 or 3. :) –  Chiron Jun 4 '13 at 15:32
    
In one particular diagnostic session, we found that 1 wire loose will not get you a MIL (Malfunction Indicator Lamp aka Check Engine Light) during slow to moderate driving. However, when I took it out on the e-way and stomped on it, after about 5 seconds of severe shuddering we did get the light. :-) –  Brian Knoblauch Jun 4 '13 at 16:22
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Interesting. I'll keep that in mind for future diagnostics. But I think we can both agree that a single plug wire being loose at idle, shouldn't cause a flashing CEL/MIL. It could conceivably cause it to pop a steady CEL/MIL, especially if the injection system uses the plugs for ion sensing duties, but I don't believe that's the case here. –  Chiron Jun 4 '13 at 17:49
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