Car hesitating and shaking.

ANSWER : It is very possible that you have a valve cover gasket or spark plug tube seal leak on your vehicle. These type of leaks will allow oil to leak onto the spark plugs causing misfires. When the engine misfires due to oil getting on the spark plug, the engine oil will burn. Since oil and tires are both petroleum products, they will both smell similar when they are burning. I would recommend having an oil leak inspection performed by a qualified professional to determine if there is an oil leak. Consider YourMechanic as an Oil/Fluid leak inspection can be peformed at your home or office.

ANSWER : Hi there. What had happened is the wrong key set the security to the vehicle. This is to prevent the vehicle from starting with the wrong keys. Try removing the battery cables (+) and (-) for 13 minutes. During that time, put the original key in the ignition and turn it on. Activate everything in the car even though there is no power. Then remove the key and hook up the battery cables. The computer should have reset and reset the security. If the security is still being tripped, then I recommend seeking out a professional, such as one from Your Mechanic, to help you

ANSWER : There are reports that the replacement alternators will not communicate with the engine computer and will not charge correctly. I recommend using only the manufacturer approved replacement part. It can be new or remanufactured but approved for use in the vehicle. Some lower cost alternators on the aftermarket will have charging problems since they will not communicate with the ECM on the vehicle and will stop charging.

ANSWER : This may be related to many different things that can cause the engine to struggle. One possibility may be a sign of a clogged catalytic converter. As you may already know, the catalytic converter converts toxic exhaust gases into less harmful pollutants that are suitable to be expelled into the atmosphere. When this is clogged, this causes these gases to be backed up into the exhaust system not allowing the engine to breathe properly (think of a backed up sink). When this happens, the engine is forced to work much harder to expel these gases. This often results in the engine bogging down, hesitating, shaking and causing very poor fuel economy. Typically when this happens it may also cause the catalytic converter to become very hot and in some cases turning bright red. This should also cause a check engine light to come on as the O2 sensors should be reading the incorrect amounts of oxygen in the exhaust gases if this is your problem. I would recommend having an expert from YourMechanic come to your location to diagnose and replace your catalytic converter.

ANSWER : Shaking with the a/c on can be caused by a number of reasons. The a/c compressor puts a lot of strain on the engine because the compressor is similar to being a small engine itself. When the a/c is switched on, the engine control unit should trigger components such as the idle speed/air control motor, to increase the idle slightly to compensate for the extra drag of the compressor. If that does not happen, then the additional drag can cause a low,shaky idle and even cause the engine to stall. Stalling can happen more often with the a/c on and turning the steering wheel as the power steering pump also creates drag on the engine. Excessive shaking can also be attributed to weak/broken motor mounts as well.

Have a certified technician look into the engine shake to isolate the exact cause.

ANSWER : You don’t mention the Check Engine Light being on, but if so, check trouble codes before any other diagnostic activity – usually saves time! Good call on your initial repair – oil in the spark plug well can short the spark plug, causing a "miss" from that cylinder. It’s possible you have a bad ignition coil (or more), or some other problem like a blown head gasket causing one or more cylinders to misfire. A professional mechanic, like a certified technician from YourMechanic, can check for good spark, good compression, and proper fuel injection on each cylinder to isolate the problem and make repairs.

ANSWER : If the shaking is occurring with the car stationary, that would not involve the wheels or driveshaft, although it could implicate the torque converter. A shaking engine diagnostic would start with the motor mounts. If those are judged solid (there are tests), one should assess the mechanical condition of the engine by checking cylinder compression.

The reason for that is if cylinder compression varies too much, that variance alone can account for this symptom. If the cylinder compression is too low or varies too much from high reading cylinder to low reading cylinder, one would then try to rule out easily repairable items like a mispositioned timing belt or chain. Of course, if compression issues are traced to valve train problems, the heads have to be serviced.

Other potential causes of the vibration are a broken harmonic balancer, engine ignition timing being off, and flexplate and/or torque converter damage or imbalance. Prior to getting involved with diagnosing an imbalance in something as hidden as the torque converter, though, the engine should be put on a scope to determine if there is something going on in individual cylinder firing conditions that would account for the vibration. Varying power output from individual cylinders, due to possible fuel and ignition system problems, obviously will cause vibration: you could have a bad coil, plug, injector, and so forth. A scope makes that diagnostic easy.

I recommend having a certified mechanic, such as one from YourMechanic, come to your location to determine why the engine is shaking and suggest any necessary repairs.

ANSWER : I believe that it is very possible that you could have another ignition coil going bad. If the first ignition coil resolved the issue you were having and it was actually faulty, it is not unlikely that another ignition coil may have gone bad at the same time. If your vehicle has a Check Engine Light, this would be helpful in determining which cylinder is misfiring. Whichever misfire code is stored in your PCM, will tell the technician which cylinder is having the issue. If the affected cylinder is not the same one you recently had issues with, you likely have another faulty ignition coil.