Intermittent Stalling

ANSWER : Hi There,
This may be related to low fuel pressure, faulty or dirty fuel injectors, a faulty or dirty idle air control valve (this relays information about air intake to the computer which makes fuel adjustments), or potentially a faulty fuel pressure regulator or fuel pump. Fuel delivery problems will typically not allow the proper amount of fuel to be delivered to the cylinders which results in a lean fuel condition which can cause backfiring or simply cause the motor not to start as a result of fuel starvation. I would recommend having an expert from YourMechanic come to your location to diagnose and inspect your vehicle.

ANSWER : Without visually inspecting the problem, it would be hard to see why the stall happens. These vehicles have many possible problems and you replaced most of them. This is not to say that is it is impossible for one of these parts to be failing again. Since this is an intermittent problem, this makes the issue tougher to diagnose. Only way to find the problem is to visually inspect the vehicle, scan for codes, check fuel pressure, and check for spark as the problem is happening. If you want to have this diagnosed, a technician from YourMechanic can come to your car’s location to inspect your stalling issue and determine what is going wrong.

ANSWER : You should have the check engine light and engine scanned to see if the engine may be running lean due to low fuel pressures or clogged injectors. You should also have the mass airflow sensor cleaned and checked for proper readings and replace if not within specifications. The vehicle runs richer in colder weather and may be the reason for not stalling. You should clean injectors, clean throttle body and idle control valve then clean mass air sensor and relearn idle.

ANSWER : Hello. Thank you for writing in. Fuel pump issues and malfunctions do often start out intermittently. If the fuel pump is the problem, you can expect it to increase in frequency until it completely fails. It would be beneficial to know why he thought it was a fuel pump issue, but a fuel pressure test may be able to shed more light on the situation. A step you can take, specifically in cold weather, is to turn the key to the "On" position for a moment before turning over the engine. This will give the pump a moment to prime before the engine makes its demands. Catching that warning light and reading those codes is another step you can take to make sure it’s the same problem occurring again. Get a second opinion, do some further testing, or just go ahead and replace the fuel pump considering the first diagnosis.

ANSWER : Hey there. You cannot operate a motor vehicle on public roadways if you know for a fact that it stalls unexpectedly. So the first order of business is to STOP driving the car especially given the two frankly lurid examples of near catastrophic crashes that you have described in your question. The second issue is easier: although there are AT LEAST a dozen obvious causes of the symptom you are reporting, and it is laborious to track down each possible "cause," the problem is definitely fixable.

You either have fuel or ignition related component(s), possibly both, that are intermittently cutting out. It might be possible to obtain enough data via your car’s OBD-II DTC interface to diagnose the problem at the time of failure and/or get in the general "area" of the failure. Given the age of the car, one issue to keep in mind is you could have a combination of problems that ultimately cause the stall. To have this problem scoped out, a certified professional from YourMechanic can come to your home or office to inspect the stalling issue and have this corrected.

ANSWER : This problem may involve the heavy duty test tools, such as an oscilloscope, but it seems likely that the ignition control module has all but completely failed. It lives in/on the distributor – a hot place with a lot of vibration. Testing the spark path from trigger to spark plug is needed: from the magnetic pickup in the distributor to the ignition control module to the cap & rotor, plug wires, and then the plugs themselves.

I would recommend having a mobile, professional mechanic, such as one from YourMechanic, perform an inspection to determine why the car is starting and dying and give an accurate assessment of the damage and cost estimate for repairs.

ANSWER : Failures in the charging circuit (alternator, etc.) do not typically cause a rough idle. A faulty throttle position sensor and/or clogged fuel injectors can cause the engine to run roughly but those are just two among many, many potential causes of a rough running engine. What will help you is a rough idle diagnostic during which the individual cylinder firing patterns can be evaluated on a scope. Those firing patterns will allow the mechanic to see if perhaps there is "a" or a couple bad cylinders and also whether the engine is experiencing a fuel system versus ignition system problem and in which cylinders. On an engine with so many miles, 240,000 in your case, compression should be tested in each cylinder as wear in the engine could potentially cause enough imbalance, from cylinder to cylinder, to cause the engine to run roughly. You have to keep in mind that typically there will be multiple issues with an old engine, for example you could have dirty fuel injectors, a sticky EGR valve and fouled plugs due to the inevitable leakage from old valve stem oil seals, or any of a number of other combinations. The best thing to do, to see if you can get additional service life out of the engine, and you likely can, is to methodically and carefully go through the list of possibilities. YourMechanic certified technicians specialize in just that so if you set up a diagnostic, a technician will get to the bottom of this for you and give you repair options so that the engine can be restored to reasonable operating condition.

ANSWER : Check the ignition coil on your engine. If the coil in new with the distributor, then the problem could be the computer or module of the vehicle. An ECM or PCM will cause the ignition system to shut down if there is too much heat. If the vehicle has an external ignition module, then the module could be getting too hot causing the engine to stall out. If you need further assistance with your engine stalling, then seek out a professional, such as one from Your Mechanic, to help you.