Have new fuel pump and filter.. truck will stall while driving...will restart but will only rough idle.. turning ignition switch completly off and on..restarts and eventually rpms return to normal..drives a few miles and same problem occurs..this also has happened after parking overnight and trying to start in the morning..
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Car idle is rough Inspection Service & Cost
A rough idling engine can be caused by a number of issues, some of them are serious while others tend to be minor, but the symptoms remain pretty much the same. The car will feel rough and bouncy when the engine is running. The car will also idle below its regular speed, display inconsistent RPMs and may produce a shaking, skipping or slipping sound when the vehicle is running.
While a rough idling engine may seem to be a simple inconvenience it often indicates a deeper problem within the engine. The vehicle should be inspected and repaired as soon as possible because small problems have a way of turning into expensive repairs.
How this system works:
The idle speed of an engine is basically the rotational speed the engine runs on when it is un-coupled from the drivetrain and the throttle pedal is not being depressed. The idle speed is measured in the revolutions per minute of the crankshaft.
When an engine is running at idle speed it generates enough power to smoothly operate equipment such as the water pump, alternator, and power steering but not enough power to move the vehicle itself. A passenger car will usually idle between 600 RPMs and 1000 RPMs. A properly functioning idle should run smoothly without skipping or slipping.
Common reasons for this to happen:
Dirty Fuel Injectors: The fuel injection system injects fuel into the cylinders, which creates a mix of air, and fuel to ignite and burn. Fuel injectors have tiny nozzles to spray the fuel into the cylinder and they can become clogged over time. clogged or failing fuel injector creates a lack of fuel in the vehicle's engine. This can cause a rough idle, it can also cause symptoms such as slow acceleration or the car not feeling as if it has enough power. If the problem is addressed early, it is possible to clean the injectors, which will restore them to full function. If this condition is not addressed in a timely manner the injectors will need to be replaced. Incorrect Idle Speed: While the average idle speed falls between 600 to 1,000 RPMs, if your vehicle is experiencing a rough idle it could be due to an incorrect idle speed setting. A trained mechanic can easily adjust the idle speed, and it should stay at the proper speed. If an adjusted idle speed becomes inconsistent or changes at random intervals there may be a bigger problem that needs to be explored. Vacuum Leak: If the vacuum system has a leak, it can seriously affect the ability of the vehicle's computer to regulate the air to fuel ratio. This can lead to a rough idle and if the problem is not addressed the car may experience slow acceleration and a lack of power. Vacuum leaks should be inspected and repaired immediately. Incorrectly Installed or Damaged Plugs: Spark plugs are responsible for creating the spark that allows the vehicle to burn fuel. If spark plugs are improperly installed or malfunctioning, the idle speed can be affected. The vehicle's engine may vibrate or there may be slipping or straining sounds coming from the engine. Defective or Clogged Fuel Pump: A rough idle can be related to fuel delivery issues. The fuel pump, which is responsible for pulling fuel from the gas tank to the fuel injectors, can become clogged or defective. If this happens the engine will not get enough fuel, which can cause a rough idle, sputtering, stalling and even slow acceleration. Clogged Fuel Filter: A clogged fuel filter can cause similar problems. The job of the fuel filter is to screen out contaminants in the fuel, over time it will become clogged and need to be replaced. A rough idle is one symptom of a clogged fuel filter. Failing Electrical Components: A problem or failure in the ignition system or various electronic components can cause a rough idle. If this is the case, the problem will usually get worse as RPMs increase. Common culprits include the ignition control module, plug wires, coils, and spark plugs. Defective Airflow Sensor: A defective airflow sensor can be responsible for a rough idle. A mass airflow sensor detects the amount of air coming into the fuel injection system and sends that information to the vehicle's computer. The computer uses that data to deliver the proper amount of fuel to the air in the vehicle. Over time these sensors can malfunction or become dirty. One of the first symptoms of a malfunctioning airflow sensor is a rough idle. The car may also accelerate slowly and even stutter or stall as the problem progresses. Dirty Oxygen Sensor: Oxygen sensors measure how rich or lean the gases are as they exit the combustion chamber. Depending on the results, the amount of fuel entering the engine is adjusted by the vehicle computer. The ultimate goal is to maintain an ideal mixture that produces the lowest emissions. A dirty or failing oxygen sensor will usually trigger the check engine light and can lead to a rough idle, lower fuel efficiency and failed emission test.
If your car stalled while you were driving it, look for an obvious reason first. Check to make sure you have fuel in the tank (if your gas gauge is working). Do not sit there and crank the car over, trying to get it to start, as you will quickly wear down the battery if it's not already bad. Check the probable causes for this kind of problems:- Ignition The ignition system is composed of: ignition switch, neutral safety switch, security bypass, plugs, wires (if applicable) and a coil, or in the case of coil-over systems, many coils. The ignition is also tied into the computer. The crank and cam sensors tell the engine where top dead center is. Though these sensors do not usually cause a no start, if they break, the computer will go into "limp home mode," which allows you to get the car to a service station. The car will run badly, and may stall out on you. If the plug wires, plugs or coils are bad and are causing the engine to misfire, the engine will run rough. This may also cause the car to stall when driving. Generally, it will start back up, but it may be difficult to keep the car running. Fuel The fuel system is composed of a fuel pump, fuel filters, and fuel injectors or a carburetor. Some cars have a throttle body---this looks similar to a carburetor and has only one or two fuel injectors in the middle of it. The injectors feed all of the cylinders. In a multi-port system, each cylinder has its own injector. Should the fuel pump go bad, the car will stall while you are driving, as no fuel is getting pumped up to the engine. Bad injectors in a multi-port system will make the car run rough, which can cause a stalling situation, but generally, the car will restart. Other Problems There are other problems that can make a car stall---in the ignition system, the fuel system or in the drivetrain. If the timing belt breaks, the car will stall. If the computer itself stops working, the car will stall. Neither item will allow a car to start back up until it is repaired.All vehicles have an idle air motor or valve. The idle air is governed by the computer and changes the idle. When you turn on the air compressor, you use some engine resources. This makes the idle speed on the engine drop. The computer senses this drop and sends information to the idle air to turn up the idle so the car does not stall. If this part breaks, when you slow down to a stop or to turn a corner, the car may stall. Because the running of a vehicle is complicated, there are many more things that can cause a vehicle to stall. These are the most common things that can cause a car to stall. Other things include wiring, fuses, relays, other sensors not working properly or at all, a bad alternator or a bad battery, or an overheating problem, just to name a few.
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signs of a bad fuel pressure regulator. the vehicle runs rough, the engine will not start usually in the mornings. many times engine starts but stalls shortly after starting. a bad regulator can result in fouled plugs. black soot on plugs, blake smoke from tailpipe, running rough, stalling. you could have residue in fuel tank and need to change fuel filter again. have a very good day !!
Check your 91 Accord's ignition coil. The coil goes bad at apprx. 150k miles and cause the car to run rough, hard to start(long cranking time) in the morning, stall after the vehicle has warmed up, cut out while driving and backfire horribly when accelerating from a standstill.
Sounds the EGR valve and EVP sen is bad even if you tested it. The EGR valve cntrols idle and if carbon up will make the car stall or idle high and low (rpms going up and down) This was common on all cars during that time. I would say replace the EGR valve and senosr. This should take care of the problem. One more thing have the fuel pressure check on the car.
you might want to chk. the crank sensor and or cam sensor. sounds more to me that it could be fuel problem. chk. fuel pressure. pump could be on its way out. don't be fooled by hearing the pump running as they sound like they are pumping but there not, at least not enought pressure to keep it running. pressure should be around 50 p.s.i.