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Plugs Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Thu, 14 Feb 2002 12:44:57
In Reply to: Boost Problem. Quite long., Jeff M., Thu, 14 Feb 2002 11:13:35 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Stuttering or misfire under high boost is almost always an ignition problem. The higher the pressure in the cylinder, the harder it is for the spark to jump. No spark, and you get a 'miss', which makes the engine feel like it's stumbling.
First thing, check your spark plug gap. Make sure it's set to the value on the decal under the hood or in the manual. Too big a gap makes it harder for the spark to jump. If the plugs look old or worn, replace them. I recommend getting the specified NGKs. Other plugs may work, but if you're having ignition problems, it makes sense not to experiment. Remember, always check the plug gap when you install new plugs - never assume they'll come out of the box set right for your car.
If plugs don't fix it, start checking the rest of the system. When the pressure increases in the cylinder under boost, that spark will look for some other weakiness in the ignition system to leak out. Make sure the inside of the distributor cap is clean, and replace cap and rotor if they're old. Old plug wires can cause problems by exhibiting higher than normal resistance, or allowing sparks to jump to other places (like chassis) - not in the cylinder where they belong.
Of course, make sure your timing is correct.
Leaks in the system under boost wouldn't cause this kind of problem. Think of it this way - air in that big hose is already metered - the ECU has measured it and scheduled fuel for that amount of air. If some of that air has leaked out on the way to the cylinder, you'll end up with two things - first, a richer mixture (fuel for lots of air, but less than lots of air) and lower cylinder pressures. Rich mixture and lower compression BOTH would help to reduce knock or misfiring.
Check your ignition system - that's probably where the problem lies.
posted by 140.157....
, Thu, 14 Feb 2002 12:44:57 <-- Viewing This Message
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