Car missing after starting

Answer 1

Perhaps it was stolen... But, on the off-chance you mean the engine is misfiring, you need to approach it systematically. Rule out the following and the engine should smooth out: 1) Perform the scheduled maintenance required by your owner's manual. Replace spark plugs, air filter, ignition cables as required. Inspect the plugs as you take them out. You can tell a lot about your engine by reading your plugs. A good diagram is located at http://www.aa1car.com/library/sprkplg2.htm. All of the plugs will look similar and the color will be white to tan in a properly running engine. Ensure that the plugs are properly tightened. There are two styles of plugs...with and without gaskets. A good shop manual will give the tightening instructions. 2) Fuel--Check the fuel filler cap. A missing or damaged cap can cause the emissions system to improperly set the fuel mixture. Is the engine fuel-starved or running too rich? Is there water in the fuel? Is the fuel clean? Drain the fuel tank if you suspect contaminated fuel. Fuel starvation or flooding can occur from a malfunctioning electronic control module (ECM) or emission sensors. Take it to a mechanic and ask him to read the codes. Many parts stores will read the codes for free. Repair/replace the malfunctioning component. Mention the symptoms to the mechanic while he's reading the codes and ask if he wouldn't mind taking a listen...a trained ear can save you a lot of troubleshooting. If the ECM doesn't show codes, replace the fuel filter, ensure the fuel pump is pumping sufficiently (check fuel pressure on fuel injected engines or delivery volume for carburetted systems). 3) Ignition--If you see a 'light show' under your hood at night, you definitely need new ignition cables. Even if you don't see arcing and sparking, the cables degrade over time, especially when they are mis-routed close to hot engine parts. If you have over 80K miles on the engine, just replace them--ONE AT A TIME (so you don't scramble the firing order). As you unplug the cables, inspect the distributor cap for thin black cracks (carbon tracks). They will bleed the spark to ground and cause the affected cylinder to misfire. A cheap way to check the ignition is to clamp a clean spark plug to something metal that doesn't move when the engine starts. One at a time, plug each ignition cable to that plug and start the engine. You should see a nice, hot, blue spark jump the gap. CAUTION, you don't want your hands anywhere close because the spark can do you some serious harm, especially on the newer capacitive discharge systems. 4) Timing--Obtain a timing light and follow the instructions in a shop manual. Adjust as necessary. 5) Compression--Check the compression of each cylinder by screwing a pressure gage into each spark plug hole, one at a time, and starting the engine momentarily. The proper method is to perform both a dry and wet (squirt about a half ounce of oil into the cylinder) reading. A big difference (>20 psi) between wet and dry or between cylinders indicates problems that are going to send you to the shop. A difference between wet and dry means that the rings are worn. A difference between cylinders can indicate leaking valves or a cracked head or block or leaking head gasket. 6) Exhaust--Power loss will result if the exhaust is blocked. Inspect for crushed pipes or obstructions in the tailpipe (Do kids still put potatos in tailpipes?) A catalytic converter can become blocked for various reasons, too. There was a notice out a while back regarding double-walled exhaust pipes. The pipe will get hot and expand uniformly but when the car goes through water, the outer wall will rapidly contract and cause the hot inner wall to buckle and obstruct the exhaust flow. A trained eye might be able to diagnose this. It is very rare to see this today because nobody uses double-walled pipes anymore. Tell your mechanic what you have done. It will save you money because it will help the mechanic rule out problems and shorten the diagnosis time and it will also impress your mechanic that you are not an easy mark (not to say that all mechanics are crooked, mind you).