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You are driving down the turnpike and then experience a feeling you instantly recognize, but just as quickly overlook.  The engine stumbles for a moment then regains its pace.  Just as soon as the motor settles down, the misfire reappears, and you’re stuck with the sinking feeling that accompanies all automotive problems, “Oh No!  I don’t have the time or the resources to spend on a pickup repair!”  

There are many items that can cause the motor to miss or run roughly. The chief culprits are simple: spark or fuel.  These routinely manifest in spark plugs, plug wires, the coil(s), or the fuel-delivery system.   

To determine which of these is instigating your difficulty you should start your investigation with an under hood analysis. Defective ignition wires, blocked injectors, or motor mechanical malfunctions are all probable.  Launch your examination with an under the hood inspection. Look for crumbled or cracked vacuum hoses. Check out the spark plug wires for chafing or signs of arching to the engine block. If the car is due for routine service, this should be done prior to spending too much time on an examination.

A complete tune-up including spark plugs, spark plug wires, distributor cap and rotor (if so equipped), fuel filter, and air filter will go a long way in repairing the most common problems. If a misfire is still present after a complete tune-up is executed, then an analysis of motor mechanical problems may be necessary. A vacuum test using a vacuum gauge should be performed. An engine should draw at least 15 pounds of vacuum at idle when connected to a vacuum hose that is connected to the intake manifold. The vacuum should be smooth and not fluctuating.

A severely fluctuating vacuum gauge is an evidence that there is a valve train malfunction, such as a broken valve or slipped timing belt. Retarded ignition timing can cause exceptionally depressed motor vacuum. A compression check should be executed on the motor to determine if lower than customary compression is present in any cylinder. Refer to a manufacturer’s specific service manual for compression specifications. As a general rule, the compression should be above 120 PSI and the lowest cylinder should be at least 80% of the highest cylinder. If the above tests do not indicate a failure, an analysis of the fuel and ignition system must be completed.  

There are other more dire causes: computer or wiring problems, deterioration in the rotating mass (pistons, rods, and crank bearings), valves and the heads can fail or distort. Cooling difficulties might permit overheating, and any number of gaskets could have pushed. Most are rare and were most likely caused by your failure to address simpler problems in the ignition or injection.  

If you are incapable to enact the tests requisite to home in on the actual agent of the misfire it is certainly best to approach a respectable vehicle repair store and have them check out your truck.  

Guessing at the problem and throwing parts at it will only serve to run up your expense and possibly make it more difficult to determine the true cause of the problem with your car.  Save yourself time and cash by performing maintenance according to manufacturer’s recommendations and take it to your nearest Auto Service Experts repair facility for a free diagnostic whenever you have any vehicle performance problems.

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