Question about Cars & Trucks
I have fitted new plugs h/t leads coil packs fuel filter air filter reco injectors another good DFI module Fuel pump pressure 250 psi and vol 2.5 ltr per min comp pressures 180 psi all cyls manifold vac seems ok With wheels locked and in drive engine will miss and breakdown when rpm is increased
Check for collapsed catalyic converter innards as it will block the exhaust ( most noticeable at revs) tap the outside case with the heel of the hand and if ti rattles it may be your problem
Posted on Jan 19, 2013
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Posted on Jan 02, 2017
Have you changed the plugs, if any are fouled out or if any are worn, it takes more to fire it under load and may be spark knocking because one of the plugs can't fire off all the gas and cause it to skip or idle rough.
Posted on Jan 18, 2010
You may have some contaminated fuel,use a additive called heet,for moister,and lucas fuel treatment,these are premium additives,do not just use any brand,these I know will fix the problem if it is in the fuel.
Posted on Jan 25, 2010
SOURCE: x type jag 3.0 V6
What causes a cylinder to misfire? Basically, it's one of three things: loss of spark; the air/fuel mixture is too far out of balance to ignite; or loss of compression. Loss of spark includes anything that prevents coil voltage from jumping the electrode gap at the end of the spark plug. Causes include worn, fouled or damaged spark plugs, bad spark plug wires or even a cracked distributor cap. A weak coil or excessive rotor gas inside a distributor would affect all cylinders, not just a single cylinder.
If you find a P0300 random misfire code, it means the misfire is random and is moving around from cylinder to cylinder. The cause here would likely be something that upsets the engine's air/fuel mixture, such as a major vacuum leak, a leaky EGR valve or unusually low fuel pressure (weak pump or faulty pressure regulator).
In the case of a steady misfire, isolating the misfiring cylinder is the first step in diagnosing the problem. The old-fashioned method for finding a weak cylinder is to temporarily disconnect each of the spark plug wires, one at a time, while the engine is idling. When there's no change in the idle speed, then you have pinpointed the weak cylinder.
A power balance test will tell you the same thing, but this requires some hookups and an engine analyzer. A power balance test is preferable to pulling plug wires, because it keeps you away from the voltage and prevents the voltage from causing any damage to the electronics in the ignition system.
When a plug wire is physically disconnected from a spark plug, the high voltage surge from the coil cannot follow its normal path to ground through the plug wire and spark plug, so it passes back through the coil. Most ignition systems are robust enough to withstand such voltage backups intermittently but not on a prolonged basis. If the coil or ignition module is already weak, it may push the component over the brink causing it to fail.
Posted on Nov 12, 2010
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